"uuid","repository link","title","author","contributor","publication year","abstract","subject topic","language","publication type","publisher","isbn","issn","patent","patent status","bibliographic note","access restriction","embargo date","faculty","department","research group","programme","project","coordinates"
"uuid:78b3ee0c-71ac-41f6-8564-53b3e1e4d31c","http://resolver.tudelft.nl/uuid:78b3ee0c-71ac-41f6-8564-53b3e1e4d31c","Measurements of morphodynamics of a sheltered beach along the Dutch Wadden Sea","van der Lugt, M.A. (TU Delft Coastal Engineering; Deltares); Bosma, Jorn W. (Universiteit Utrecht); de Schipper, M.A. (TU Delft Coastal Engineering); Price, Timothy D. (Universiteit Utrecht); van Maarseveen, Marcel C. G. (Universiteit Utrecht); van der Gaag, P. (TU Delft Lab Hydraulic Engineering); Ruessink, Gerben (Universiteit Utrecht); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Aarninkhof, S.G.J. (TU Delft Civil Engineering & Geosciences)","","2024","A field campaign was carried out at a sheltered sandy beach with the aim of gaining new insights into the driving processes behind sheltered beach morphodynamics. Detailed measurements of the local hydrodynamics, bed-level changes and sediment composition were collected at a man-made beach on the leeside of the barrier island Texel, bordering the Marsdiep basin that is part of the Dutch Wadden Sea. The dataset consists of (1) current, wave and turbidity measurements from a dense cross-shore array and a 3 km alongshore array; (2) sediment composition data from beach surface samples; (3) high-temporal-resolution RTK-GNSS beach profile measurements; (4) a pre-campaign spatially covering topobathy map; and (5) meteorological data. This paper outlines how these measurements were set up and how the data have been processed, stored and can be accessed. The novelty of this dataset lies in the detailed approach to resolve forcing conditions on a sheltered beach, where morphological evolution is governed by a subtle interplay between tidal and wind-driven currents, waves and bed composition, primarily due to the low-energy (near-threshold) forcing. The data are publicly available at 4TU Centre for Research Data at: https://doi.org/10.4121/19c5676c-9cea-49d0-b7a3-7c627e436541 (Van der Lugt et al., 2023).","","en","journal article","","","","","","","","","Civil Engineering & Geosciences","","Coastal Engineering","","",""
"uuid:08100443-b972-48cc-9582-ec2478cc247f","http://resolver.tudelft.nl/uuid:08100443-b972-48cc-9582-ec2478cc247f","The impact of modulational instability on coastal wave forecasting using quadratic models","Akrish, G. (TU Delft Environmental Fluid Mechanics); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Zijlema, Marcel (TU Delft Environmental Fluid Mechanics); Smit, P.B. (Sofar Ocean Technologies)","","2024","Coastal wave forecasting over large spatial scales is essential for many applications (e.g., coastal safety assessments, coastal management and developments, etc.). This demand explains the necessity for accurate yet effective models. A well-known efficient modelling approach is the quadratic approach (often referred to as frequency-domain models, nonlinear mild-slope models, amplitude models, etc.). The efficiency of this approach stems from a significant modelling reduction of the original governing equations (e.g., Euler equations). Most significantly, the description of wave nonlinearity essentially collapses into a single mode coupling term determined by the quadratic interaction coefficients. As a result, it is expected that the efficiency achieved by the quadratic approach is accompanied by a decrease in prediction accuracy. In order to gain further insight into the predictive capabilities of this modelling approach, this study examines six different quadratic formulations, three of which are of the Boussinesq type and the other three are referred to as fully dispersive. It is found that while the Boussinesq formulations reliably predict the evolution of coastal waves, the predictions by the fully dispersive formulations tend to be affected by false developments of modulational instability. Consequently, the predicted wave fields by the fully dispersive formulations are characterized by unexpectedly strong modulations of the sea-swell part and associated unexpected infragravity response. The impact of the modulational instability on wave prediction based on the quadratic approach is further demonstrated using existing laboratory results of bichromatic and irregular wave conditions.","Modulation instability; Spectral modelling; Quadratic modelling; Coastal waves; Wave nonlinearity; Infragravity waves","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:734b79ec-8e6b-4f1f-b50d-111414f8d4ff","http://resolver.tudelft.nl/uuid:734b79ec-8e6b-4f1f-b50d-111414f8d4ff","Dune erosion during storm surges: A review of the observations, physics and modelling of the collision regime","van Wiechen, P.P.J. (TU Delft Coastal Engineering); de Vries, S. (TU Delft Coastal Engineering); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Aarninkhof, S.G.J. (TU Delft Hydraulic Engineering)","","2023","Dune erosion during storm surges can lead to excessive damage to the dune system with devastating floods as a potential consequence. A risk assessment of areas protected by dunes can be facilitated by an understanding and description of the physical processes that take place. Field measurements, knowledge of underlying processes and numerical modelling have developed with time, which enabled a more comprehensive description and new predictive techniques. This review concerns dune erosion in the collision regime, and summarises relevant observations, describes underlying processes and explains existing models predicting dune erosion. Observations of dune erosion consist of field observations, laboratory experiments and manipulative field campaigns. The underlying physical processes that contribute to dune erosion are divided into processes that contribute to sediment transport due to hydrodynamic forcing, which occurs in the surf and swash zone, and sediment transport due to avalanching, which occurs in the swash zone, on the dune face and on the dune crest. The existing dune erosion models that are discussed here contain (empirical) equilibrium profile models and process-based models, which can both be a valuable tool for the risk assessment of storm surges. However, model uncertainties still remain, as specific processes are not yet fully understood and described. Examples are the influences of wave obliquity, sediment grain size, and vegetation on the dune face. By improving our knowledge through research and reducing these uncertainties, we can further improve our predictive models. This could eventually lead to more accurate predictions, more complete risk assessments, and sandy coastlines which are more resilient to excessive dune erosion and possible floods.","dune erosion; storm surges; collision regime; review","en","review","","","","","","","","","","Hydraulic Engineering","Coastal Engineering","","",""
"uuid:3fdd202f-1e2e-411d-a90f-5001508b3871","http://resolver.tudelft.nl/uuid:3fdd202f-1e2e-411d-a90f-5001508b3871","Quantifying spit growth and its hydrodynamic drivers in wind-dominated lake environments","van Kouwen, Niels C. (Royal HaskoningDHV; Student TU Delft); Ton, A.M. (TU Delft Coastal Engineering); Vos, S.E. (TU Delft Coastal Engineering; Baars-CIPRO); Vijverberg, Thomas (Royal Boskalis Westminster); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Aarninkhof, S.G.J. (TU Delft Hydraulic Engineering)","","2023","Many sand spits are morphodynamically complex landforms, that are either analysed with complex and expensive computational models or at a conceptual level. Therefore, most case studies on spits in different environments are descriptive. A novel method based on the use of polar coordinates was devised to quantitatively analyse spit morphodynamics in a non-tidal, wind-dominated lake environment, using the Marker Wadden islands in Lake Markermeer, the Netherlands, as a case study. A high-resolution morphological data set allowed for the quantification of sedimentation processes around two spits, in two distinctive depth zones. Spit-platform growth is governed by alongshore currents that transport sediment over the spit-platform into deeper waters; the size of the spit-platform in turn affects the growth of the spit around the mean water level. Insight in this complex interplay of processes is crucial to understand spit behaviour in low-energy lake environments. At the Marker Wadden the submerged spit-platform grows during high energy wind events while the emerged spit part grows under mild to moderate energy conditions. With this new method we can quantitatively explore the role of different wave and flow conditions and predict spit growth direction in non-tidal, wind-dominated environments, beyond the level of conceptual descriptions.","Low-energy; Marker Wadden (Lake Markermeer, the Netherlands); Spit growth; Spit-platform","en","journal article","","","","","","","","","","Hydraulic Engineering","Coastal Engineering","","",""
"uuid:2088b05e-b259-400b-9a8d-75523d9b353e","http://resolver.tudelft.nl/uuid:2088b05e-b259-400b-9a8d-75523d9b353e","Optimising the wave attenuation of bamboo fences using the numerical wave model SWASH","Alferink, M. (TU Delft Environmental Fluid Mechanics); Gijón Mancheño, A. (TU Delft Hydraulic Structures and Flood Risk); Suzuki, Tomohiro (Flanders Hydraulics Research); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2023","The coastline of Demak, Indonesia, has been eroding during the
last 15 years. Coastal retreat in Demak is caused by a combination
of mangrove deforestation and local subsidence due to groundwater
extraction in the nearby city of Semarang. To restore the lost mangrove
forest, permeable dams, consisting of bamboo poles with a
brushwood filling, have been built to attenuate the waves, facilitate
sedimentation at their land side, and thus create a suitable habitat
for mangroves. However, existing designs required frequent brushwood
maintenance. Therefore, a new type of design is proposed,
consisting of only vertical bamboo poles without a filling of brushwood.
Nevertheless, the hydrodynamic performance of this type of
structure is not known. This study assesses the wave transformation
through structures formed by bamboo poles for the physical
conditions of Demak, Indonesia, with the numerical wave model
SWASH. Field measurements and WaveWatch III data are analyzed
to obtain the design conditions for the structures in Demak.
SWASH is validated against laboratory experiments, and applied
to investigate different structure designs. The model shows that for
a structure consisting of two rows of bamboo poles, the transmission
rate Et/Ei decreases from 75% to 55% when the row spacing
in the wave direction is increased from sx = 0.42 m to sx =5.8
m. Even larger spacings do not result in less transmission, and
at least three rows are needed to have a transmission rate lower
than 50 % - a common wave reduction target used in restoration
efforts with structures. This study thus identifies potential strategies
to maximize wave attenuation by bamboo structures, which
can be used to reduce wave attack along muddy coasts without
the need of a brushwood filling. Hereby it provides an economically
and user friendly alternative with respect to the previous
brushwood structure designs, as it requires less material costs and
maintenance.","SWASH; Nature Based Solutions; Wave Attenuation; Mangroves","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:786b07c9-2141-4cf3-a5a2-7eecae296186","http://resolver.tudelft.nl/uuid:786b07c9-2141-4cf3-a5a2-7eecae296186","Cross-shore transformation of bound and free infragravity waves off the Dutch coast","Rutten, J. (TU Delft Environmental Fluid Mechanics); Tissier, M.F.S. (TU Delft Environmental Fluid Mechanics); Zhang, Xinyi (Student TU Delft); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); van Wiechen, P.P.J. (TU Delft Coastal Engineering); de Vries, S. (TU Delft Coastal Engineering); Rijnsdorp, D.P. (TU Delft Environmental Fluid Mechanics); Mol, Jan Willem (Rijkswaterstaat); Wilmink, Rinse (Rijkswaterstaat)","Cox, Dan (editor)","2023","Infragravity (IG) waves are key drivers for coastal erosion and thus need to be properly included in process-based modelling of coastal hazards. Uncertainties remain regarding the offshore boundary conditions for these long waves. Typically, only bound IG waves are included at the boundary, which means that the possible contribution of free IG waves, such as those radiated from distant coastlines, is neglected. Recent studies however suggest that incoming free IG waves could be significant, particularly in semi-enclosed basins such as the North Sea where they could contribute to coastal hazards (e.g., Reniers et al., 2021, Rijnsdorp et al. 2021). The objective of this work is to improve the understanding of the incoming IG wave field along the Dutch coast. We will quantify how bound and free IG waves develop in intermediate water depths and assess in which conditions (onshore directed) free IG waves become significant.","","en","conference paper","Coastal Engineering Research Council","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:dd1a1937-ef67-4a3b-8fde-a4a373c88bff","http://resolver.tudelft.nl/uuid:dd1a1937-ef67-4a3b-8fde-a4a373c88bff","Measurements and Modeling of Pore-Pressure Gradients in the Swash Zone Under Large-Scale Laboratory Bichromatic Waves","Kranenborg, J. W.M. (University of Twente; Deltares); Pauli, T. (University of Twente; Now at Nebest BV); Jacobsen, N. G. (Vattenfall Denmark); van der Werf, J. J. (University of Twente; Deltares); Dionisio Antonio, S. (University of Twente); Campmans, G. H.P. (University of Twente); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Hulscher, S. J.M.H. (University of Twente)","","2023","The present work presents physical laboratory measurements of surface elevation and pore water pressures in a fine sand bed under bichromatic waves in a large-scale laboratory experiment. This was done at three cross-shore locations in the swash zone, with pressures being measured at different depths in the bed. The measurements show that the pore pressure signal decays and shifts with increased depth. These measurements are used to validate a practical model, based on the theory of Yamamoto et al. (1978, https://doi.org/10.1017/S0022112078003006) and Guest and Hay (2017, https://doi.org/10.1002/2016JC012257). The model corresponds well with the measurements (nRMSE < 0.2 and R2 > 0.95 for most probes) and shows that a frequency-based model can reproduce the pressures in the bed, despite the bed being exposed during dry periods. Furthermore, the model provides the opportunity to calculate pressure gradients, both throughout the bed and at the bed surface. These modeled pressure gradients at the bed surface show that the vertical pressure gradient can have an important impact on the Shields parameter, thereby influencing sediment transport.","","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:f567f476-0545-4e94-bbd3-c40cdcbdc212","http://resolver.tudelft.nl/uuid:f567f476-0545-4e94-bbd3-c40cdcbdc212","Including the effect of depth-uniform ambient currents on waves in a non-hydrostatic wave-flow model","Rijnsdorp, D.P. (TU Delft Environmental Fluid Mechanics); van Rooijen, Arnold (University of Western Australia); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Tissier, M.F.S. (TU Delft Environmental Fluid Mechanics); de Wit, F.P. (TU Delft Environmental Fluid Mechanics; Svašek Hydraulics); Zijlema, Marcel (TU Delft Environmental Fluid Mechanics)","","2023","Currents can affect the evolution of waves in nearshore regions through altering their wavenumber and amplitude. Including the effect of ambient currents (e.g., tidal and wind-driven) on waves in phase-resolving wave models is not straightforward as it requires appropriate boundary conditions in combination with a large domain size and long simulation duration. In this paper, we extended the non-hydrostatic wave-flow model SWASH with additional terms that account for the influence of a depth-uniform ambient current on the wave dynamics, in which the current field can be taken from an external source (e.g., from observations or a circulation model). We verified the model ability by comparing predictions to results from linear theory, laboratory experiments and a spectral wave model that accounts for wave interference effects. With this extension, the model was able to account for current-induced changes to the wave field (i.e., changes to the wave amplitude, length and direction) due to following and opposing currents, and two classical examples of sheared currents (a jet-like current and vortex ring). Furthermore, the model captured the wave dynamics in the presence of strong opposing currents. This includes reflections of relatively small amplitude waves at the theoretical blocking point, and transmission of breaking waves beyond the theoretical blocking point for larger wave amplitudes. The proposed model extension allows phase-resolving models to more accurately and efficiently simulate the wave dynamics in coastal regions with tidal and/or wind-driven flows.","Non-hydrostatic; SWASH; Wave–current interactions","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:76b83523-5b61-4f2a-ba13-b2625a1f1058","http://resolver.tudelft.nl/uuid:76b83523-5b61-4f2a-ba13-b2625a1f1058","Modeling Multi-Fraction Coastal Aeolian Sediment Transport With Horizontal and Vertical Grain-Size Variability","van IJzendoorn, Christa (TU Delft Coastal Engineering); Hallin, E.C. (TU Delft Coastal Engineering; Lund University); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); de Vries, S. (TU Delft Coastal Engineering)","","2023","Grain size affects the rates of aeolian sediment transport on beaches. Sediment in coastal environments typically consists of multiple grain-size fractions and exhibits spatiotemporal variations. Still, conceptual and numerical aeolian transport models are simplified and often only include a single fraction that is constant over the model domain. It is unclear to what extent this simplification is valid and if the inclusion of multi-fraction transport and spatial grain-size variations affects aeolian sediment transport simulations and predictions of coastal dune development. This study applies the numerical aeolian sediment transport model AeoLiS to compare single-fraction to multi-fraction approaches for a range of grain-size distributions and spatial grain-size scenarios. The results show that on timescales of days to years, single-fraction simulations with the median grain size, D50, often give similar results to multi-fraction simulations, provided the wind is able to mobilize all fractions within that time frame. On these timescales, vertical variability in grain size has a limited effect on total transport rates, but it does influence the simulation results on minute timescales. Horizontal grain-size variability influences both the total transport rates and the downwind bed grain-size composition. The results provide new insights into the influence of beach sediment composition and spatial variability on total transport rates toward the dunes. The findings of this study can guide the implementation of grain-size variability in numerical aeolian sediment transport models.","aeolian processes; AeoLiS; beaches; coastal processes; grain size; modeling; nearshore processes; sediment transport","en","journal article","","","","","","","","","","","Coastal Engineering","","",""
"uuid:df138b42-996d-4c9f-b181-bd4112dfb291","http://resolver.tudelft.nl/uuid:df138b42-996d-4c9f-b181-bd4112dfb291","A mild-slope formulation based on Weyl rule of association with application to coastal wave modelling","Akrish, G. (TU Delft Environmental Fluid Mechanics); Smit, Pieter (Sofar Ocean Technologies); Zijlema, Marcel (TU Delft Environmental Fluid Mechanics); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2023","Weyl rule of association, proposed by Hermann Weyl for quantum mechanics applications (Weyl, 1931), can be used to associate between the dispersion relation of water waves and a non-local pseudo-differential operator. The central result of this study is that this operator correctly approximates the Dirichlet-to-Neumann operator derived for linear waves over a slowly varying bathymetry. This opens the door to a formal use of Weyl's operational calculus, and consequently, allowing straightforward derivations and generalizations of water waves’ models over mild slopes. Specifically, within the framework of linear wave theory, the formulation based on Weyl rule of association provides a generalized mild-slope model which does not impose a limit on the spectral width. Most significantly, the mild-slope formulation based on Weyl rule of association allows to derive a general linear kinetic equation for which the widely used energy balance equation (the central equation of forecasting models such as SWAN and WAVEWATCH) serves as a special case. This result not only provides a formal link between the deterministic description (i.e., Euler equations) and the stochastic description (i.e., the energy balance equation), but also establishes the theoretical foundations for the statistical description of bathymetry-induced wave interferences. Such a statistical description is especially important over coastal waters, where through the interaction with the bathymetry, waves are rapidly scattered and tend to form focal zones and associated interference patterns.","A mild-slope formulation; Phase-averaged models; Spectral modelling of coastal waves; Statistical wave interferences; The energy balance equation; Weyl rule of association","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:99e88b1c-75e8-4ed4-8207-75b33cea4b96","http://resolver.tudelft.nl/uuid:99e88b1c-75e8-4ed4-8207-75b33cea4b96","Drivers of cross-shore chenier dynamics off a drowning coastal plain","Tas, S.A.J. (TU Delft Environmental Fluid Mechanics); van Maren, D.S. (TU Delft Environmental Fluid Mechanics; East China Normal University; Deltares); Helmi, Muhammad (Universitas Diponegoro); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2022","A chenier is a beach ridge, consisting of sand and/or shells, overlying a muddy substrate. In this paper, we explore the cross-shore dynamics of cheniers in their ‘active’ phase, i.e. the phase between their formation and their landing on the shore and can no longer be reached by daily wave and tidal influences. While cheniers described in literature are known to only migrate onshore until they reach a stable position with their crest level above tidal influences, observations in Demak suggest the existence of an alternative stable state, highly dynamic on the short term, but stable on the longer term. To explore this alternative stable state, we developed an idealised chenier model to investigate cross-shore chenier dynamics under daily wave and tidal influences. The model is able to predict both onshore and offshore migration; onshore migration is mainly driven by wave action, while offshore migration is induced by a tidal phase lag, or the effect of the storm season. For certain combinations of waves, tide (incl. phase lag) and a storm season effect, the model predicts a dynamically stable chenier. In absence of a phase lag and storm season effect, the model yields a ‘classic’ stable chenier that welds onto the shoreline by onshore migration.","Cheniers; Modelling; Morphodynamics; Tide; Waves","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:219cdb99-e105-48a1-92b9-dda7d4c2ac31","http://resolver.tudelft.nl/uuid:219cdb99-e105-48a1-92b9-dda7d4c2ac31","SWAN SurfBeat-1D","Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Zijlema, Marcel (TU Delft Environmental Fluid Mechanics)","","2022","The Simulating WAves Nearshore (SWAN) model has been extended with an infragravity module to predict the Wave-Group-Forced (WGF) infragravity response to a frequency-directional sea-swell spectrum at a mildly sloping alongshore uniform beach. To that end the SWAN model has been extended with an WGF-infragravity source term denoted Ssb where the subscript denotes surfbeat. The corresponding WGF infragravity energy model has been verified with a set of benchmark tests using the infragravity amplitude model of Reniers et al. (2002). Next the implementation of the energy balance in SWAN has been validated with both prototype-scale laboratory experiments and field observations, showing a good comparison with observations not affected by the nodal structure of the (partially) standing infragravity waves. This suggests that the model is capable of providing improved infragravity boundary conditions in relatively shallow water compared to the typical assumption of equilibrium forcing conditions using for instance Hasselmann's equilibrium theory (Hasselmann, 1962). These infragravity boundary conditions can subsequently can be used by other more sophisticated models to compute runup, overtopping and dune erosion.","Bound and free infragravity waves; Field and laboratory validation; Spectral modeling","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:4c08ad65-db9a-402c-86bf-1b21bd23a799","http://resolver.tudelft.nl/uuid:4c08ad65-db9a-402c-86bf-1b21bd23a799","Reconstruction of Directional Spectra of Infragravity Waves","Matsuba, Yoshinao (IHE Delft Institute for Water Education); Roelvink, D. (IHE Delft Institute for Water Education); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Rijnsdorp, D.P. (TU Delft Environmental Fluid Mechanics); Shimozono, Takenori (University of Tokyo)","","2022","Understanding directional spectra of infragravity (IG) waves composed of free and bound components is required due to their impacts on various coastal processes (e.g., coastal inundation and morphological change). However, conventional reconstruction methods of directional spectra relying on linear wave theory are not applicable to IG waves in intermediate water depths (20–30 m) due to the presence of bound waves. Herein, a novel method is proposed to reconstruct directional spectra of IG waves in intermediate depth based on weakly nonlinear wave theory. This method corrects cross-spectra among observed wave signals by taking account of the nonlinearity of bound waves in order to reconstruct directional spectra of free IG waves. Numerical experiments using synthetic data representing various directional distributions show that the proposed method reconstructs free IG wave directional spectra more accurately than the conventional method. The method is subsequently applied to observations of severe sea-states at two field sites. At these sites, free IG waves are not isotropic and have clear peak directions. Numerical modeling of the wave fields shows that these peak directions correspond to the reflection of IG waves from the shore and/or coastal structures. Additionally, the validity of the underlying weakly nonlinear wave theory of the present method is assessed by a newly proposed method employing bispectral analysis. The bound wave response generally agrees with the theory at the field sites but deviates slightly for energetic sea states. The applicability of the present method on a sloping bottom is further discussed by an analytical solution.","directional spectra; infragravity waves; nonlinear waves","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2023-01-02","","","Environmental Fluid Mechanics","","",""
"uuid:496e509d-61f8-4e9b-bc7d-381a69427741","http://resolver.tudelft.nl/uuid:496e509d-61f8-4e9b-bc7d-381a69427741","Depth-Resolved Modelling of Intra-Swash Morphodynamics Induced by Solitary Waves","Kranenborg, Joost W.M. (University of Twente); Campmans, Geert H.P. (University of Twente); Jacobsen, Niels G. (Deltares); van der Werf, Jebbe J. (University of Twente; Deltares); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Hulscher, Suzanne J.M.H. (University of Twente)","","2022","We present a fully coupled 2DV morphodynamic model, implemented in OpenFOAM® that is capable of simulating swash-zone morphodynamics of sandy beaches. The hydrodynamics are described by the Reynolds-averaged Navier–Stokes (RANS) equations with a (Formula presented.) turbulence model and the Volume of Fluid (VoF) approach for discriminating between air and water. Sediment transport is described in terms of bedload and suspended load transport. We show that the default divergence scheme in OpenFOAM can become numerically unstable and lead to negative sediment concentrations, and propose a solution to avoid this problem. The model performance is assessed in terms of surface elevation, flow velocities, runup, suspended sediment concentrations, bed profile evolution and sediment transport volumes by comparing with measurements of field-scale (wave height of 0.6 m) solitary waves. The model shows reasonable agreement in terms of hydrodynamics and predicts the correct sediment transport volumes, although the deposition is predicted more onshore compared to the measurements. This is partially attributed to an overprediction of the runup. The model shows that the suspended sediment concentration displays a strong vertical dependence. These results show the potential of depth-resolving models in providing more insight into morphodynamic processes in the swash zone, particularly with respect to vertical structures in the flow and suspended sediment transport.","depth-resolving model; intra-swash; morphodynamical modelling; sediment transport; solitary wave; swash zone","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:dbb4fdca-32d1-450b-bedd-4807d792fce7","http://resolver.tudelft.nl/uuid:dbb4fdca-32d1-450b-bedd-4807d792fce7","Evaluation of Implicit and Explicit Wave Dissipation Models for Submerged and Emergent Aquatic Vegetation","Ascencio, Jaime A. (Reefy); Jacobsen, Niels G. (Deltares; Vattenfall Denmark); McFall, Brian C. (U.S. Army Engineer Research and Development Center); Groeneweg, Jacco (Deltares); Vuik, V. (TU Delft Coastal Engineering; HKV Consultants); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2022","To address the important research question of whether implicit (bottom friction) or explicit (stem drag) dissipation models are most appropriate for the prediction of wave attenuation due to aquatic vegetation, the Simulating Waves Nearshore (SWAN) spectral wave model has been extended with an explicit frequency-dependent dissipation model for submerged and emergent vegetation. The new explicit model is compared to existing explicit and implicit dissipation models in SWAN, and the distinguishing features of each of the dissipation models are quantified. The present work verifies the implementation of the new and existing dissipation models, outlines their distinguishing features, and compares model predictions against experimental data. The emphasis is on the transformation of the spectral wave periods Tm0;1 and Tm 1;0 over a canopy. Model evaluation based on academic and laboratory cases allows for recommendations regarding applicability of the three dissipation models, where the new method has the broadest applicability, since it bridges the gap in applicability between the other two dissipation models. The implementation of Jacobsen, McFall, and van der A (2019; A frequency distributed dissipation model for canopies; Coastal Engineering, 150, 135-146) is publicly available in SWAN version 41.31B.","spectral energy dissipation; SWAN; Vegetated canopies","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2022-09-03","","","Coastal Engineering","","",""
"uuid:d89668b0-9b2b-4783-a0dc-ae2dc76cd4df","http://resolver.tudelft.nl/uuid:d89668b0-9b2b-4783-a0dc-ae2dc76cd4df","Chenier Formation Through Wave Winnowing and Tides","Tas, S.A.J. (TU Delft Environmental Fluid Mechanics); van Maren, D.S. (TU Delft Environmental Fluid Mechanics; East China Normal University; Deltares); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2022","Cheniers are ridges consisting of coarse-grained sediments, resting on top of the fine sediment that forms the otherwise muddy coast. In this paper, we use Delft3D to explore how cheniers are formed through wave winnowing. We identify three phases of chenier development: (a) a winnowing phase, during which mud is washed out of the seabed initially consisting of a mixture of sand and mud, (b) a sand transport phase, when the sand in the upper layer is transported onshore, and (c) a crest formation phase, during which a chenier crest rapidly develops at the landward limit of onshore sediment transport. The main mechanism driving onshore sand transport is wave asymmetry. During calm conditions, sand transport takes place within a narrow band limiting the volume of sand delivered nearshore, and therefore no chenier develops. In contrast, average storm conditions mobilize sufficient sand for a crest to develop. Our results thus reveal that chenier formation through wave winnowing does not require extreme storm conditions. Furthermore, our study showed that chenier formation through wave winnowing is a relatively slow process, with the largest time scales associated with the winnowing and sand transport. Once sufficient sand is available in the intertidal zone, the crest develops rapidly.","chenier; Delft3D; sediment transport; wave asymmetry; winnowing","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:4d278dc4-fc88-4bdc-abb2-adf7c128eb16","http://resolver.tudelft.nl/uuid:4d278dc4-fc88-4bdc-abb2-adf7c128eb16","Novel sediment sampling method provides new insights into vertical grain size variability due to marine and aeolian beach processes","van IJzendoorn, Christa (TU Delft Coastal Engineering); Hallin, E.C. (TU Delft Coastal Engineering; Lund University); Cohn, Nicholas (U.S. Army Engineer Research and Development Center); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); de Vries, S. (TU Delft Coastal Engineering)","","2022","In sandy beach systems, the aeolian sediment transport can be governed by the vertical structure of the sediment layers at the bed surface. Here, data collected with a newly developed sand scraper is presented to determine high-resolution vertical grain size variability and how it is affected by marine and aeolian processes. Sediment samples at up to 2 mm vertical resolution down to 50 mm depth were collected at three beaches: Waldport (Oregon, USA), Noordwijk (the Netherlands) and Duck (North Carolina, USA). The results revealed that the grain size in individual layers can differ considerably from the median grain size of the total sample. The most distinct temporal variability occurred due to marine processes that resulted in significant morphological changes in the intertidal zone. The marine processes during high water resulted both in fining and coarsening of the surface sediment. Especially near the upper limit of wave runup, the formation of a veneer of coarse sediment was observed. Although the expected coarsening of the near-surface grain size during aeolian transport events was observed at times, the opposite trend also occurred. The latter could be explained by the formation and propagation of aeolian bedforms within the intertidal zone locally resulting in sediment fining at the bed surface. The presented data lays the basis for future sediment sampling strategies and sediment transport models that investigate the feedbacks between marine and aeolian transport, and the vertical variability of the grain size distribution.","aeolian; coastal geomorphology; coastal processes; grain size; intertidal beach; sediment availability; sediment transport","en","journal article","","","","","","","","","","","Coastal Engineering","","",""
"uuid:6ee00ae3-9cc2-4c28-b77c-05c54ee43bd9","http://resolver.tudelft.nl/uuid:6ee00ae3-9cc2-4c28-b77c-05c54ee43bd9","North sea infragravity wave observations","Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Naporowski, Remy (Student TU Delft); Tissier, M.F.S. (TU Delft Environmental Fluid Mechanics); de Schipper, M.A. (TU Delft Coastal Engineering); Akrish, G. (TU Delft Environmental Fluid Mechanics); Rijnsdorp, D.P. (TU Delft Environmental Fluid Mechanics)","","2021","Coastal safety assessments with wave-resolving storm impact models require a proper offshore description for the incoming infragravity (IG) waves. This boundary condition is generally obtained by assuming a local equilibrium between the directionally-spread incident sea-swell wave forcing and the bound IG waves. The contribution of the free incident IG waves is thus ignored. Here, in-situ observations of IG waves with wave periods between 100 s and 200 s at three measurement stations in the North Sea in water depths of O(30) m are analyzed to explore the potential contribution of the free and bound IG waves to the total IG wave height for the period from 2010 to 2018. The bound IG wave height is computed with the equilibrium theory of Hasselmann using the measured frequency-directional sea-swell spectra as input. The largest IG waves are observed in the open sea with a maximum significant IG wave height of O(0.3) m at 32 m water depth during storm Xaver (December 2013) with a concurrent significant sea-swell wave height in excess of 9 m. Along the northern part of the Dutch coast, this maximum has reduced to O(0.2) m at a water depth of 28 m with a significant sea-swell wave height of 7 m and to O(0.1) m at the most southern location at a water depth of 34 m with a significant sea-swell wave height of 5 m. These appreciable IG wave heights in O(30) m water depth represent a lower bound for the expected maximum IG wave heights given the fact that in the present analysis only a fraction of the full IG frequency range is considered. Comparisons with the predicted bound IG waves show that these can contribute substantially to the observed total IG wave height during storm conditions. The ratio between the predicted bound-and observed total IG variance ranges from 10% to 100% depending on the location of the observations and the timing during the storm. The ratio is typically high at the peak of the storm and is lower at both the onset and waning of the storm. There is significant spatial variability in this ratio between the stations. It is shown that differences in the directional spreading can play a significant role in this. Furthermore, the observed variability along the Dutch coast, with a substantially decreased contribution of the bound IG waves in the south compared to the northern part of the Dutch coast, are shown to be partly related to changes in the mean sea-swell wave period. For the southern part of the Dutch coast this corresponds to an increased difference with the typically assumed equilibrium boundary condition although it is not clear how much of the free IG-energy is onshore directed barring more sophisticated observations and/or modeling.","Bound and free infragravity waves; Infragravity wave observations; North sea; Storm conditions","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:a26b3354-907e-4f80-b0c7-c371dd3e8b07","http://resolver.tudelft.nl/uuid:a26b3354-907e-4f80-b0c7-c371dd3e8b07","High-resolution, large-scale laboratory measurements of a sandy beach and dynamic cobble berm revetment","Blenkinsopp, Chris E. (University of Bath); Bayle, Paul M. (University of Bath); Conley, Daniel C. (Plymouth University); Masselink, Gerd (Plymouth University); Gulson, Emily (Plymouth University); Kelly, Isabel (Plymouth University); Rijper, Huub (Deltares; Royal Boskalis Westminster; Student TU Delft); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Tissier, M.F.S. (TU Delft Environmental Fluid Mechanics)","","2021","High quality laboratory measurements of nearshore waves and morphology change at, or near prototype-scale are essential to support new understanding of coastal processes and enable the development and validation of predictive models. The DynaRev experiment was completed at the GWK large wave flume over 8 weeks during 2017 to investigate the response of a sandy beach to water level rise and varying wave conditions with and without a dynamic cobble berm revetment, as well as the resilience of the revetment itself. A large array of instrumentation was used throughout the experiment to capture: (1) wave transformation from intermediate water depths to the runup limit at high spatio-temporal resolution, (2) beach profile change including wave-by-wave changes in the swash zone, (3) detailed hydro and morphodynamic measurements around a developing and a translating sandbar.","","en","journal article","","","","","","Corrigendum DOI: 10.1038/s41597-021-00874-2","","","","","Environmental Fluid Mechanics","","",""
"uuid:e665c815-37bd-4815-8fe3-4fe770bbee8b","http://resolver.tudelft.nl/uuid:e665c815-37bd-4815-8fe3-4fe770bbee8b","Global mapping of seaport operability risk indicators using open-source metocean data","Wiegel, M.F. (TU Delft Materials and Environment; Deltares); de Boer, W.P. (TU Delft Rivers, Ports, Waterways and Dredging Engineering; Deltares); van Koningsveld, M. (TU Delft Rivers, Ports, Waterways and Dredging Engineering; Van Oord); van der Hout, A.J. (TU Delft Rivers, Ports, Waterways and Dredging Engineering; Deltares); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2021","Seaport operability is key to the economic viability of ports. Metocean conditions (e.g., wind, short waves, and infragravity waves) affect this operability when certain thresholds are exceeded. This paper describes a method for the global mapping of seaport operability risk indicators using open-source metocean data. This global-scale assessment provides a geographic overview of operability risks and first-order insights into the most relevant metocean risk indicators at each location. The results show that locations around the equator and inland seas have lower operability risk than locations farther away from the equator. “Hotspots” are mainly located along the southern capes (Cape of Good Hope, Leeuwin, Horn), around the ‘Roaring Forties’, and at exposed locations along the oceans. Of the metocean parameters considered, short waves are found to be the most critical risk indicator for port operability at most locations. Using (the insights of) this study, port authorities, operators, and designers can prepare for metocean risks at an early stage and effectively respond with mitigation measures and layout adjustments to improve port operability.","Downtime; ERA5; Global mapping; Infragravity waves; Metocean; Port operability; Seaports; Short waves; Wind","en","journal article","","","","","","","","","","","Materials and Environment","","",""
"uuid:0f94abec-8f8e-4207-940a-dfdad694f568","http://resolver.tudelft.nl/uuid:0f94abec-8f8e-4207-940a-dfdad694f568","Relationship between three-dimensional radiation stress and Vortex-Force representations","Nguyen, T.D. (TU Delft Coastal Engineering; Vietnam Institute of Seas and Islands; IHE Delft Institute for Water Education); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Roelvink, D. (TU Delft Coastal Engineering; Deltares; IHE Delft Institute for Water Education)","","2021","In numerical ocean models, the effect of waves on currents is usually expressed by either vortex-force or radiation stress representations. In this paper, the differences and similarities between those two representations are investigated in detail in conditions of both conservative and nonconservative waves. In addition, comparisons between different sets of equations of mean motion that apply different representations of wave-induced forcing terms are included. The comparisons are useful for selecting a suitable numerical ocean model to simulate the mean current in conditions of waves combined with currents.","Generalized Lagrangian Mean; Mean current; Quasi-Eulerian mean; Radiation stress; Wave-current interaction","en","journal article","","","","","","","","","","","Coastal Engineering","","",""
"uuid:75277099-8390-4ccc-abbd-26eb9797d9dc","http://resolver.tudelft.nl/uuid:75277099-8390-4ccc-abbd-26eb9797d9dc","Modelling cross‐shore shoreline change on multiple timescales and their interactions","Schepper, Rob (Student TU Delft; International Marine and Dredging Consultants (IMDC Nv)); Almar, Rafael (IRD-LEGOS); Bergsma, Erwin (CNES-LEGOS; CNES Centre National d'Etudes Spatiales); de Vries, S. (TU Delft Coastal Engineering); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Davidson, Mark (Plymouth University); Splinter, Kristen (University of New South Wales)","","2021","In this paper, a new approach to model wave‐driven, cross‐shore shoreline change incorporating multiple timescales is introduced. As a base, we use the equilibrium shoreline prediction model ShoreFor that accounts for a single timescale only. High‐resolution shoreline data collected at three distinctly different study sites is used to train the new data‐driven model. In addition to the direct forcing approach used in most models, here two additional terms are introduced: a time-upscaling and a time‐downscaling term. The upscaling term accounts for the persistent effect of short‐term events, such as storms, on the shoreline position. The downscaling term accounts for the effect of long‐term shoreline modulations, caused by, for example, climate variability, on shorter event impacts. The multi‐timescale model shows improvement compared to the original ShoreFor model (a normalized mean square error improvement during validation of 18 to 59%) at the three contrasted sandy beaches. Moreover, it gains insight in the various timescales (storms to inter‐an-nual) and reveals their interactions that cause shoreline change. We find that extreme forcing events have a persistent shoreline impact and cause 57–73% of the shoreline variability at the three sites. Moreover, long‐term shoreline trends affect short‐term forcing event impacts and determine 20– 27% of the shoreline variability.","Cross‐shore sediment transport; Equilibrium shoreline modelling; Multiple timescales; ShoreFor","en","journal article","","","","","","","","","","","Coastal Engineering","","",""
"uuid:1f6ce4d2-22fd-4208-ab35-f59a76a171a7","http://resolver.tudelft.nl/uuid:1f6ce4d2-22fd-4208-ab35-f59a76a171a7","Wave transmission and drag coefficients through dense cylinder arrays: Implications for designing structures for mangrove restoration","Gijón Mancheño, A. (TU Delft Hydraulic Structures and Flood Risk); Jansen, W. (Student TU Delft); Uijttewaal, W.S.J. (TU Delft Environmental Fluid Mechanics); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); van Rooijen, A. A. (University of Western Australia); Suzuki, T. (TU Delft Environmental Fluid Mechanics; Flanders Hydraulics Research); Etminan, V. (University of Western Australia); Winterwerp, J.C. (TU Delft Environmental Fluid Mechanics)","","2021","Mangrove vegetation constitutes a natural coastal defence against waves and erosion. Despite their protective role, mangrove ecosystems have experienced continuous degradation over the last decades due to human causes. At retreating mangrove coastlines, bamboo structures are built to create new habitat for mangrove colonization. Existing structures have experienced mixed rates of success due to the lack of a scientific basis in their design. Optimizing future structure designs requires investigating the effect of the bamboo poles on waves. We consequently conducted laboratory experiments to measure wave transformation, hydrodynamic forces, and flow velocities inside cylinder arrays, mimicking bamboo poles, with varying cylinder configurations and orientations. The experiments provided relationships for wave transmission, wave reflection, and the drag coefficients for configurations with volumetric porosities between n = 0.64 − 0.9. Configurations with a small lateral spacing (causing higher blockage) and a relatively longer streamwise spacing (causing less sheltering) exhibit larger forces and dissipation per element. Such arrangements enable optimizing wave dissipation at locations where the wave direction has low variability over the year. Placing the poles horizontally instead of vertically increases the forces and wave dissipation per element in relatively deeper water. Based on the experiments, we developed a conceptual analytical model that predicts wave reflection and dissipation through cylinder arrays, including blockage and sheltering. The model can reproduce the influence of cylinder arrangement on wave transformation, and it suggests that accurate predictions of sheltering and wave reflection are important to find optimal designs. Overall, these results provide useful insights on how to model and optimize the design of structures for mangrove restoration.","Bamboo structure; Building with nature; Dense cylinder arrays; Drag coefficient; Flume experiments; Mangrove restoration; Wave dissipation; Wave reflection","en","journal article","","","","","","","","","","","Hydraulic Structures and Flood Risk","","",""
"uuid:fc5dd17b-0d89-41df-9fd0-cf840e4d0d39","http://resolver.tudelft.nl/uuid:fc5dd17b-0d89-41df-9fd0-cf840e4d0d39","Free Infragravity Waves in the North Sea","Rijnsdorp, D.P. (TU Delft Environmental Fluid Mechanics); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Zijlema, Marcel (TU Delft Environmental Fluid Mechanics)","","2021","Infragravity waves are low-frequency surface waves that can impact a variety of nearshore and oceanic processes. Recent measurements in the North Sea showed that significant bursts of infragravity energy occurred during storm events. Using a spectral wave model, we show that a substantial part of this energy was radiated from distant shorelines where it was generated by the incident sea-swell waves. These radiated infragravity waves can cross the North Sea basin and reach distant shorelines. The origin of the infragravity wave energy varied between the different storms, and particularly depends on where largest sea-swell waves made landfall. Along the coastlines of the North Sea, shoreward directed infragravity waves that originate from a remote source were non-negligible during storm events. This suggests that radiated infragravity waves can potentially contribute to coastal dynamics and hazards away from their region of generation.","","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:63c0651d-bbdb-46aa-bbef-ef6deb8aca27","http://resolver.tudelft.nl/uuid:63c0651d-bbdb-46aa-bbef-ef6deb8aca27","Simulating wave runup on an intermediate–reflective beach using a wave-resolving and a wave-averaged version of XBeach","de Beer, A. F. (Deltares; Student TU Delft); McCall, R. T. (Deltares); Long, J. W. (St. Petersburg Coastal and Marine Science Center; University of North Carolina); Tissier, M.F.S. (TU Delft Environmental Fluid Mechanics); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2021","The prediction of wave runup, as well as its components, time-averaged setup and the time-varying swash, is a key element of coastal storm hazard assessments, as wave runup controls the transitions between morphodynamic response types such as dune erosion and overwash, and the potential for flooding by wave overtopping. While theoretically able to simulate the dominant low-frequency swash, previous studies using the infragravity-wave–resolving model XBeach (XBSB) have shown an underestimation of the observed swash variance and wave runup, which was in part related to the absence of incident-band swash motions in the model. Here, we use an incident-band wave-resolving, non-hydrostatic version of the XBeach model (XBNH) to simulate wave runup observed during the SandyDuck '97 experiment on an intermediate–reflective sandy beach. The results show that the XBNH model describes wave runup and the individual setup and swash components well. We subsequently examine differences in wave runup prediction between the XBSB and XBNH models and find that the XBNH model is a better predictor of wave runup than XBSB for this beach, which is due to better predictions of both the incident-band and infragravity-band swash. For a range of beach states from reflective to dissipative it is shown that incident-band swash is underestimated by XBSB relative to XBNH, in particular for reflective conditions. Infragravity-band swash is shown to be lower in XBSB than XBNH for most conditions, including dissipative conditions for which the mean difference is 16% of the deep water wave height. The difference in infragravity-band swash in XBNH relative to XBSB is shown to mainly be the result of processes occurring outside the swash zone, but approximately 15% of the difference is caused by explicitly resolving incident-band wave motions within the swash zone, such as swash-swash interactions, which inherently cannot be simulated by wave-averaged models.","Infragravity waves; Non-hydrostatic modeling; Runup; Swash; XBeach","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2021-03-30","","","Environmental Fluid Mechanics","","",""
"uuid:2025fc04-5e7e-4509-8834-3eb3b19f1ae9","http://resolver.tudelft.nl/uuid:2025fc04-5e7e-4509-8834-3eb3b19f1ae9","Efficient two-layer non-hydrostatic wave model with accurate dispersive behaviour","de Ridder, M.P. (Deltares); Smit, Pieter B. (Sofar Ocean Technologies); van Dongeren, Ap R. (Deltares; IHE Delft Institute for Water Education); McCall, Robert T. (Deltares); Nederhoff, Kees (Deltares-USA); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2021","A 2-layer non-hydrostatic model with improved dispersive behaviour is presented. Due to the assumption of a constant non-hydrostatic pressure distribution in the lower layer, the dispersive behaviour is improved without much additional computational time. A comparison with linear wave theory showed that this 2-layer model gives a better result for the dispersion relation and shoaling of waves in intermediate water. This means that the 2-layer model is applicable in shallow and intermediate water depths (up to relative depths kh equals 4), whereas the 1-layer model is only applicable in shallow water depths (kh smaller than 1). Three laboratory experiments, including a fringing reef and a barred beach, were used to validate the presented mode for different hydrodynamic conditions. Based on these results, it can be concluded that the 2-layer model can be applied to accurately simulate the bulk wave height and spectral properties. The low frequency wave height, the setup and in particular the second order statistics contain more scatter, but the model accurately captured the general trend. Furthermore, the model showed good results for complex bathymetries in shallow to intermediate water.","Dispersive behaviour; Non-hydrostatic model; Wave modelling; XBeach","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2021-05-05","","","Environmental Fluid Mechanics","","",""
"uuid:45d31353-c1d4-4590-8126-9f555d61129a","http://resolver.tudelft.nl/uuid:45d31353-c1d4-4590-8126-9f555d61129a","Modelling statistical wave interferences over shear currents","Akrish, G. (TU Delft Environmental Fluid Mechanics); Smit, Pieter (Sofar Ocean Technologies); Zijlema, Marcel (TU Delft Environmental Fluid Mechanics); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2020","Wave forecasting in ocean and coastal waters commonly relies on spectral models based on the spectral action balance equation. These models assume that different wave components are statistically independent and as a consequence cannot resolve wave interference due to statistical correlation between crossing waves, as may be found in, for instance, a focal zone. This study proposes a statistical model for the evolution of wave fields over non-uniform currents and bathymetry that retains the information on the correlation between different wave components. To this end, the quasi-coherent model (Smit & Janssen, J. Phys. Oceanogr., vol. 43, 2013, pp. 1741-1758) is extended to allow for wave-current interactions. The outcome is a generalized action balance model that predicts the evolution of the wave statistics over variable media, while preserving the effect of wave interferences. Two classical examples of wave-current interaction are considered to demonstrate the statistical contribution of wave interferences: (1) swell field propagation over a jet-like current and (2) the interaction of swell waves with a vortex ring. In both examples cross-correlation terms lead to development of prominent interference structures, which significantly change the wave statistics. Comparison with results of the SWAN model demonstrates that retention of cross-correlation terms is essential for accurate prediction of wave statistics in shear-current-induced focal zones.","surface gravity waves; wave scattering","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:4ad2d7d7-df5a-43b2-a05b-ab8401173fc4","http://resolver.tudelft.nl/uuid:4ad2d7d7-df5a-43b2-a05b-ab8401173fc4","Hydro-Morphological Characterization of Coral Reefs for Wave Runup Prediction","Scott, Fred (Deltares; W.F. Baird Associates); Antolinez, Jose A.A. (Deltares); McCall, Robert (Deltares); Storlazzi, Curt (North Central Climate Science Centre); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Pearson, S.G. (TU Delft Coastal Engineering; Deltares)","","2020","Many coral reef-lined coasts are low-lying with elevations <4 m above mean sea level. Climate-change-driven sea-level rise, coral reef degradation, and changes in storm wave climate will lead to greater occurrence and impacts of wave-driven flooding. This poses a significant threat to their coastal communities. While greatly at risk, the complex hydrodynamics and bathymetry of reef-lined coasts make flood risk assessment and prediction costly and difficult. Here we use a large (>30,000) dataset of measured coral reef topobathymetric cross-shore profiles, statistics, machine learning, and numerical modeling to develop a set of representative cluster profiles (RCPs) that can be used to accurately represent the shoreline hydrodynamics of a large variety of coral reef-lined coasts around the globe. In two stages, the large dataset is reduced by clustering cross-shore profiles based on morphology and hydrodynamic response to typical wind and swell wave conditions. By representing a large variety of coral reef morphologies with a reduced number of RCPs, a computationally feasible number of numerical model simulations can be done to obtain wave runup estimates, including setup at the shoreline and swash separated into infragravity and sea-swell components, of the entire dataset. The predictive capability of the RCPs is tested against 5,000 profiles from the dataset. The wave runup is predicted with a mean error of 9.7–13.1%, depending on the number of cluster profiles used, ranging from 312 to 50. The RCPs identified here can be combined with probabilistic tools that can provide an enhanced prediction given a multivariate wave and water level climate and reef ecology state. Such a tool can be used for climate change impact assessments and studying the effectiveness of reef restoration projects, as well as for the provision of coastal flood predictions in a simplified (global) early warning system.","cluster analysis; coral reefs; data mining; K-means; wave runup; XBeach","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:ebbcfdd0-e7f3-4a26-844e-7062a7cc49c3","http://resolver.tudelft.nl/uuid:ebbcfdd0-e7f3-4a26-844e-7062a7cc49c3","Uncertainties in coastal flood risk assessments in small island developing states","Parodi, Matteo U. (Deltares); Giardino, Alessio (Deltares); Van Dongeren, Ap (Deltares); Pearson, S.G. (TU Delft Coastal Engineering; Deltares); Bricker, J.D. (TU Delft Hydraulic Structures and Flood Risk); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2020","Considering the likely increase in coastal flooding in small island developing states (SIDSs) due to climate change, coastal managers at the local and global levels have been developing initiatives aimed at implementing disaster risk reduction (DRR) and adaptation measures. Developing science-based adaptation policies requires accurate coastal flood risk (CFR) assessments, which in the case of insular states are often subject to input uncertainty. We analysed the impact of a number of uncertain inputs on coastal flood damage estimates: (i) significant wave height, (ii) storm surge level and (iii) sea level rise (SLR) contributions to extreme sea levels, as well as the error-driven uncertainty in (iv) bathymetric and (v) topographic datasets, (vi) damage models, and (vii) socioeconomic changes. The methodology was tested through a sensitivity analysis using an ensemble of hydrodynamic models (XBeach and SFINCS) coupled with a direct impact model (Delft-FIAT) for a case study of a number of villages on the islands of São Tomé and Príncipe. Model results indicate that for the current time horizon, depth damage functions (DDFs) and digital elevation models (DEMs) dominate the overall damage estimation uncertainty. When introducing climate and socioeconomic uncertainties to the analysis, SLR projections become the most relevant input for the year 2100 (followed by DEM and DDF). In general, the scarcity of reliable input data leads to considerable predictive uncertainty in CFR assessments in SIDSs. The findings of this research can help to prioritize the allocation of limited resources towards the acquisitions of the most relevant input data for reliable impact estimation.","","en","journal article","","","","","","","","","","","Coastal Engineering","","",""
"uuid:ded75c83-5fbe-47b9-84c8-1ce2b5a0f1a9","http://resolver.tudelft.nl/uuid:ded75c83-5fbe-47b9-84c8-1ce2b5a0f1a9","Measurements of hydrodynamics, sediment, morphology and benthos on Ameland ebb-tidal delta and lower shoreface","van Prooijen, Bram (TU Delft Environmental Fluid Mechanics); Tissier, M.F.S. (TU Delft Environmental Fluid Mechanics); de Wit, F.P. (TU Delft Environmental Fluid Mechanics); Pearson, S.G. (TU Delft Coastal Engineering; Deltares); Holzhauer, H. (Deltares; University of Twente); Gawehn, M.A. (Deltares); Antolínez, José A. Á. (TU Delft Coastal Engineering); de Vet, P.L.M. (TU Delft Coastal Engineering; Deltares); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Wang, Zhengbing (TU Delft Coastal Engineering; Deltares); den Heijer, C. (TU Delft Management Support; Data2day); Wilmink, R.J.A. (Ministry of Infrastructure and the Environment)","","2020","A large-scale field campaign was carried out on the ebb-tidal delta (ETD) of Ameland Inlet, a basin of the Wadden Sea in the Netherlands, as well as on three transects along the Dutch lower shoreface. The data have been obtained over the years 2017-2018. The most intensive campaign at the ETD of Ameland Inlet was in September 2017. With this campaign, as part of KustGenese2.0 (Coastal Genesis 2.0) and SEAWAD, we aim to gain new knowledge on the processes driving sediment transport and benthic species distribution in such a dynamic environment. These new insights will ultimately help the development of optimal strategies to nourish the Dutch coastal zone in order to prevent coastal erosion and keep up with sea level rise. The dataset obtained from the field campaign consists of (i) single-and multi-beam bathymetry; (ii) pressure, water velocity, wave statistics, turbidity, conductivity, temperature, and bedform morphology on the shoal; (iii) pressure and velocity at six back-barrier locations; (iv) bed composition and macrobenthic species from box cores and vibrocores; (v) discharge measurements through the inlet; (vi) depth and velocity from X-band radar; and (vii) meteorological data. The combination of all these measurements at the same time makes this dataset unique and enables us to investigate the interactions between sediment transport, hydrodynamics, morphology and the benthic ecosystem in more detail. The data provide opportunities to calibrate numerical models to a high level of detail. Furthermore, the open-source datasets can be used for system comparison studies. The data are publicly available at 4TU Centre for Research Data at https://doi.org/10.4121/collection:seawad (Delft University of Technology et al., 2019) and https://doi.org/10.4121/collection:kustgenese2 (Rijkswaterstaat and Deltares, 2019). The datasets are published in netCDF format and follow conventions for CF (Climate and Forecast) metadata. The http://data.4tu.nl (last access: 11 November 2020) site provides keyword searching options and maps with the geographical position of the data.","","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:8e8fdbc5-18ed-43e1-a7f6-59554cd7408a","http://resolver.tudelft.nl/uuid:8e8fdbc5-18ed-43e1-a7f6-59554cd7408a","Numerical experiments on resonant wave amplification over a fringing reef","Lasserre, Camila Gaido (Student TU Delft); Tissier, M.F.S. (TU Delft Environmental Fluid Mechanics); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Pearson, S.G. (TU Delft Coastal Engineering); Bricker, J.D. (TU Delft Hydraulic Structures and Flood Risk)","Lynett, Patrick (editor)","2020","Waves are important drivers for reef hydrodynamics, and therefore strongly contribute to flooding over reef-lined coasts. While high-frequency waves are largely dissipated when they propagate over the reef flat due to breaking and friction, low-frequency (LF) waves are generally able to reach the back-reef beach. There, they can reflect and form (quasi-) standing wave patterns, which under resonant conditions can lead to disproportionally high run-up on the beach (e.g., Pequignet et al., 2009; Gawehn et al., 2016). The probability of this phenomenon is expected to increase due to sea-level rise (e.g., Pequignet et al., 2009). In this study, we numerically investigate long wave resonance and the processes enhancing or limiting the resonant amplification of long waves over the reef flat. Besides the role of frictional dissipation (e.g., Pomeroy et al. 2012), we investigate how the nonlinear transformation of long waves influences the amplification rate.","","en","conference paper","Coastal Engineering Research Council","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:2d312d8b-75c2-4e86-86b0-f7f92ae89471","http://resolver.tudelft.nl/uuid:2d312d8b-75c2-4e86-86b0-f7f92ae89471","Optimal sediment transport for morphodynamic model validation","Bosboom, J. (TU Delft Coastal Engineering); Mol, M. (MIcompany); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Stive, M.J.F. (TU Delft Coastal Engineering); de Valk, C. F. (Royal Netherlands Meteorological Institute (KNMI))","","2020","Although commonly used for the validation of morphological predictions, point-wise accuracy metrics, such as the root-mean-squared error (RMSE), are not well suited to demonstrate the quality of a high-variability prediction; in the presence of (often inevitable) location errors, the comparison of depth values per grid point tends to favour predictions that underestimate variability. In order to overcome this limitation, this paper presents a novel diagnostic tool that defines the distance between predicted and observed morphological fields in terms of an optimal sediment transport field, which moves the misplaced sediment from the predicted to the observed morphology. This optimal corrective transport field has the “cheapest” quadratic transportation cost and is relatively easily found through a parameter-free and symmetric solution procedure solving an elliptic partial differential equation. Our method, which we named effective transport difference (ETD), is a variation to a partial differential equation approach to the Monge–Kantorovich L2 optimal transport problem. As a new error metric, we propose the root-mean-squared transport error (RMSTE) as the root-mean-squared value of the optimal transport field. We illustrate the advantages of the RMSTE for simple 1D and 2D cases as well as for more realistic morphological fields, generated with Delft3D, for an idealized case of a tidal inlet developing from an initially highly schematized geometry. The results show that by accounting for the spatial structure of morphological fields, the RMSTE, as opposed to the RMSE, is able to discriminate between predictions that differ in the misplacement distance of predicted morphological features, and avoids the consistent favouring of the underprediction of morphological variability that the RMSE is prone to.","Effective transport difference; Model accuracy; Model validation; Monge–Kantorovich; Morphodynamic modelling; Optimal transport; Root-mean-squared error; Root-mean-squared transport error","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2020-08-06","","","Coastal Engineering","","",""
"uuid:9836848e-1ce2-4407-97b6-6a0e6fab4c36","http://resolver.tudelft.nl/uuid:9836848e-1ce2-4407-97b6-6a0e6fab4c36","Observations of cross-shore chenier dynamics in Demak, Indonesia","Tas, S.A.J. (TU Delft Environmental Fluid Mechanics); van Maren, D.S. (TU Delft Environmental Fluid Mechanics; Deltares); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2020","Cheniers are important for stabilising mud-dominated coastlines. A chenier is a body of wave-reworked, coarse-grained sediment consisting of sand and shells overlying a muddy substrate. In this paper we present and analyse a week of field observations of the dynamics of a single chenier along the coast of Demak, Indonesia. Despite relatively calm hydrodynamics during the one-week observational period, the chenier migrated surprisingly fast in the landward direction. The role of the tide and waves on the cross-shore chenier dynamics is explored using velocity moments as a proxy for the sediment transport. This approach shows that both tide and waves are capable of transporting the sediment of the chenier system. During calm conditions (representative for the south-east monsoon season), the tides generate a landward-directed sediment transport when the chenier crest is high relative to mean sea level. Waves only generate substantial sediment transport (direct, via skewness, and indirect, via stirring) when the chenier is submerged during periods with higher waves. The cross-shore chenier dynamics are very sensitive to the timing of tide and waves: most transport takes place when high water levels coincide with (relatively) high waves.","Cheniers; Field measurements; Indonesia; Mangroves; Muddy coast; Sediment transport","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:04c2d3c9-80e2-4c3c-a7aa-89e413ea8d71","http://resolver.tudelft.nl/uuid:04c2d3c9-80e2-4c3c-a7aa-89e413ea8d71","The relationship between sea-swell bound wave height and wave shape","de Wit, F.P. (TU Delft Environmental Fluid Mechanics); Tissier, M.F.S. (TU Delft Environmental Fluid Mechanics); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2020","The nonlinear wave shape, expressed by skewness and asymmetry, can be calculated from surface elevation or pressure time series using bispectral analysis. Here, it is shown that the same analysis technique can be used to calculate the bound superharmonic wave height. Using measured near-bed pressures from three different field experiments, it is demonstrated that there is a clear relationship between this bound wave height and the nonlinear wave shape, independent of the measurement time and location. This implies that knowledge on the spatially varying bound wave height can be used to improve wave shape-induced sediment transport predictions. Given the frequency-directional sea-swell wave spectrum, the bound wave height can be predicted using second order wave theory. This paper shows that in relatively deep water, where conditions are not too nonlinear, this theory can accurately predict the bispectrally estimated bound superharmonic wave height. However, in relatively shallow water, the mismatch between observed and predicted bound wave height increases significantly due to wave breaking, strong currents, and increased wave nonlinearity. These processes are often included in phase-averaged wind-wave models that predict the evolution of the frequency-directional spectrum over variable bathymetry through source terms in a wave action balance, including the transfer of energy to bound super harmonics. The possibility to calculate and compare with the observed bound super harmonic wave height opens the door to improved model predictions of the bound wave height, nonlinear wave shape and associated sediment transport in large-scale morphodynamic models at low additional computational cost.","Bispectrum; Bound wave height; Field measurements; Wave shape","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:19bb017f-3f04-4767-b696-73fbfd94f703","http://resolver.tudelft.nl/uuid:19bb017f-3f04-4767-b696-73fbfd94f703","Cross-shore intertidal bar behavior along the dutch coast: Laser measurements and conceptual model","Vos, S.E. (TU Delft Coastal Engineering); Spaans, Lennard (Svašek Hydraulics); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Holman, Rob (Oregon State University); McCall, Robert (Deltares); de Vries, S. (TU Delft Coastal Engineering)","","2020","Intertidal bars are naturally occurring morphological features along the waterline of sandy beaches. Present quantitative knowledge on intertidal bar behavior is limited, due to the scarcity of data resources and the limitations of traditional survey techniques. To investigate and quantify the cross-shore morphologic behavior of intertidal bars, hourly terrestrial laser scans of Kijkduin beach (The Netherlands) are used and a conceptual evolution intertidal bar model is constructed. In a six-week period in January and February 2017, a pronounced intertidal bar formed at Kijkduin beach and migrated onshore during mild wave conditions and eroded again during storm conditions. The observed maximum shoreward migration was 30 m horizontally with a maximum growth of about 1 m in the vertical direction. Onshore sediment transport fluxes peaked around 2 m3 per m width per day. In the conceptual model proposed here, run-up and overwash processes are dominant for shoreward growth and migration of the bar and submersion processes are responsible for bar destruction.","Coastal monitoring; Conceptual model; Cross-shore sediment transport; Intertidal sandbars; LiDAR","en","journal article","","","","","","","","","","","Coastal Engineering","","",""
"uuid:eaa35868-235a-4063-94ea-76d591f19e4b","http://resolver.tudelft.nl/uuid:eaa35868-235a-4063-94ea-76d591f19e4b","The impact of wind on flow and sediment transport over intertidal flats","Colosimo, I. (TU Delft Environmental Fluid Mechanics); de Vet, P.L.M. (TU Delft Coastal Engineering; Deltares); van Maren, D.S. (TU Delft Environmental Fluid Mechanics; Deltares); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Winterwerp, J.C. (TU Delft Environmental Fluid Mechanics); van Prooijen, Bram (TU Delft Environmental Fluid Mechanics)","","2020","Sediment transport over intertidal flats is driven by a combination of waves, tides, and wind-driven flow. In this study we aimed at identifying and quantifying the interactions between these processes. A five week long dataset consisting of flow velocities, waves, water depths, suspended sediment concentrations, and bed level changes was collected at two locations across a tidal flat in the Wadden Sea (The Netherlands). A momentum balance was evaluated, based on field data, for windy and non-windy conditions. The results show that wind speed and direction have large impacts on the net flow, and that even moderate wind can reverse the tidal flow. A simple analytical tide–wind interaction model shows that the wind-induced reversal can be predicted as a function of tidal flow amplitude and wind forcing. Asymmetries in sediment transport are not only related to the tide–wind interaction, but also to the intratidal asymmetries in sediment concentration. These asymmetries are influenced by wind-induced circulation interacting with the large scale topography. An analysis of the shear stresses induced by waves and currents revealed the relative contributions of local processes (resuspension) and large-scale processes (advection) at different tidal flat elevations.","Intertidal flats; Sediment storage; Sediment transport; Suspended sediment fluxes; Tide–wind interaction; Wind-driven flow","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:9b6b35d0-a86d-41b6-acf7-e6cd01d34a99","http://resolver.tudelft.nl/uuid:9b6b35d0-a86d-41b6-acf7-e6cd01d34a99","Tidal Wave Propagation in the Flat Basin Under Wind Monsoon Climate","Phan, M.H. (TU Delft Coastal Engineering); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Stive, M.J.F. (TU Delft Coastal Engineering); Ye, Qinghua (Deltares)","Nguyen, Kim Dan (editor); Guillou, Sylvain (editor); Gourbesville, Philippe (editor); Thiébot, Jérôme (editor)","2020","Tide is influenced due to not only mainly tide generating force but also local wind and weather patterns. The East Asian monsoons cause strong seasonal climatic variations in the Mekong Delta. A two-dimensional, barotropic numerical model was employed to investigate the dynamics of tidal wave propagation in the South China Sea with a particular interest for its characteristics along the Mekong deltaic coast under wind monsoon climate. The results reveal that wind monsoon climate could causes damped or amplified tidal amplitudes around Mekong deltaic coast approximately 2–3 cm due to the changing atmospheric pressure, the tangential stress of wind over the water surface, and wind enhanced bottom friction. The monsoon climate influences rather strongly on the M2 semidiurnal tide system in the eastern Mekong deltaic coast, meanwhile the monsoon climate controls K1 diurnal tide in the western region of Mekong delta.","Delft3D; Mekong deltaic coast; Tidal wave propagation; Wind monsoon climate","en","book chapter","Springer","","","","","Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2020-08-29","","","Coastal Engineering","","",""
"uuid:de593a28-a273-4e73-ac03-49228fe3af8c","http://resolver.tudelft.nl/uuid:de593a28-a273-4e73-ac03-49228fe3af8c","Performance evaluation of wave input reduction techniques for modeling inter-annual sandbar dynamics","de Queiroz, Bruna (Deltares); Scheel, F. (Deltares); Caires, Sofia (Deltares); Walstra, D.J.R. (TU Delft Coastal Engineering; Deltares); Olij, Derrick (PwC); Yoo, Jeseon (Korea Institute of Ocean Science and Technology); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); de Boer, W.P. (TU Delft Rivers, Ports, Waterways and Dredging Engineering; Deltares)","","2019","In process-based numerical models, reducing the amount of input parameters, known as input reduction (IR), is often required to reduce the computational effort of these models and to enable long-term, ensemble predictions. Currently, a comprehensive performance assessment of IR-methods is lacking, which hampers guidance on selecting suitable methods and settings in practice. In this study, we investigated the performance of 10 IR-methods and 36 subvariants for wave climate reduction to model the inter-annual evolution of nearshore bars. The performance of reduced wave climates is evaluated by means of a brute force simulation based on the full climate. Additionally, we tested how the performance is affected by the number of wave conditions, sequencing, and duration of the reduced wave climate. We found that the Sediment Transport Bins method is the most promising method. Furthermore, we found that the resolution in directional space is more important for the performance than the resolution in wave height. The results show that a reduced wave climate with fewer conditions applied on a smaller timescale performs better in terms of morphology than a climate with more conditions applied on a longer timescale. The findings of this study can be applied as initial guidelines for selecting input reduction methods at other locations, in other models, or for other domains.","Input reduction; Markov Chain; Monte Carlo; Morphodynamics; Process-based modeling; Sandbars; Sequencing; Wave climate","en","journal article","","","","","","","","","","","Coastal Engineering","","",""
"uuid:aab92ce9-8fbf-462d-8e26-174ad1a9f36b","http://resolver.tudelft.nl/uuid:aab92ce9-8fbf-462d-8e26-174ad1a9f36b","Characterizing wave shape evolution on an ebb-tidal shoal","de Wit, F.P. (TU Delft Environmental Fluid Mechanics); Tissier, M.F.S. (TU Delft Environmental Fluid Mechanics); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2019","Field measurements of waves and currents were obtained at ten locations on an ebb-tidal shoal seaward of Ameland Inlet for a six-week period. These measurements were used to investigate the evolution of the near-bed velocity skewness and asymmetry, as these are important drivers for wave-induced sediment tranport. Wave shape parameters were compared to traditionally used parameterizations to quantify their performance in a dynamic area with waves and tidal currents coming in from different directions over a highly variable bathymetry. Spatially and temporally averaged, these parameterizations compared very well to observed wave shape. However, significant scatterwas observed. The largest deviations fromthe parameterizationwere observed at the shallowest locations, where the contribution of wave-induced sediment transport was expected to be the largest. This paper shows that this scatter was caused by differences in wave-breaking, nonlinear energy transfer rate, and spatial gradients in tidal currents. Therefore, it is proposed to include the prior evolution of the wave before reaching a location in future parameterizations in numerical modeling instead of only using local parameters to predict wave shape.","Asymmetry; Ebb-tidal shoal; Field measurements; Skewness; Ursell number; Wave shape","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:ae4257d3-0ef9-49ce-bd1b-cc0e499462aa","http://resolver.tudelft.nl/uuid:ae4257d3-0ef9-49ce-bd1b-cc0e499462aa","Wave-Skewness And Current-Related Ebb-Tidal Sediment Transport: Observations And Modeling","Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); de Wit, F.P. (TU Delft Environmental Fluid Mechanics); Tissier, M.F.S. (TU Delft Environmental Fluid Mechanics); Pearson, S.G. (TU Delft Coastal Engineering; Deltares); Brakenhof, L.B. (Universiteit Utrecht); van der Vegt, M. (Universiteit Utrecht); Mol, J. (Rijkswaterstaat); van Prooijen, Bram (TU Delft Environmental Fluid Mechanics)","","2019","A combination of observations and modeling of wave-and current-related sediment transport at the ebb-tidal delta of Ameland, The Netherlands, has been used to examine the dominant sediment transport contributions shaping the ebb-tidal delta. The calibrated model shows a good comparison with the observations for a range of conditions. The results show distinctly different transport modes and directions for current and wave-dominated conditions respectively, with a significant contribution owing to the skewness of the waves emphasizing the importance of wave non-linearity in shaping the ebb-tidal delta.","","en","conference paper","World Scientific Publishing","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2019-12-01","","","Coastal Engineering","","",""
"uuid:bcc96320-13e0-4106-99b5-1e1c106b351c","http://resolver.tudelft.nl/uuid:bcc96320-13e0-4106-99b5-1e1c106b351c","Aeolian modelling of coastal landform development","van Westen, B. (Deltares); de Vries, S. (TU Delft Coastal Engineering); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); den Bieman, Joost P. (Deltares); Hoonhout, B.M. (Van Oord); Rauwoens, P. (Katholieke Universiteit Leuven); van Puijenbroek, M.E.B. (Wageningen University & Research)","","2019","In order to improve the current aeolian modeling, a process-based model is developed by implementing biological and physical processes adapted from different existing models. The current version of the model is capable of simulating barchan and parabolic dunes and the initial stage of coastal dune formation: Embryo dunes. Potentially the model can be used to determine the influence of tidal ranges, storm frequencies, armoring, salinity and precipitation on dune building processes. This will result in a greater insight in the general behavior of coastal systems and on the other hand the model can also be used for engineering purposes.","","en","conference paper","World Scientific Publishing","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2019-12-01","","","Coastal Engineering","","",""
"uuid:14f328ed-d0b6-4bc4-be31-f2c9c8a08231","http://resolver.tudelft.nl/uuid:14f328ed-d0b6-4bc4-be31-f2c9c8a08231","Observations of mixing and transport on a steep beach","Brown, Jenna A. (Naval Post Graduate School of Engineering and Applied Sciences); MacMahan, Jamie H. (Naval Post Graduate School of Engineering and Applied Sciences); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics; University of Miami); Thornton, Ed B. (Naval Post Graduate School of Engineering and Applied Sciences); Shanks, Alan L. (University of Oregon); Morgan, Steven G. (University of California); Gallagher, Edie L. (Franklin and Marshall College, Lancaster)","","2019","Surfzone mixing and transport on a sandy, steep (∼1/8 slope), reflective beach at Carmel River State Beach, California, are described for a range of wave and alongshore flow conditions. Depth-limited wave breaking occurred close to the shore due to the steepness of the beach, creating a narrow surf/swash zone (∼10 m wide). Fluorescent Rhodamine dye was released as a slug in the surfzone, and the temporal and spatial evolution was measured using in-situ dye sensors. Dye concentration measured as a function of time reveals sharp fronts that quickly decay resulting in narrow peaks near the dye release, which subsequently broaden and decrease in peak concentration with alongshore distance. The measurements indicate two stages of mixing and transport occur inside the surfzone on the steep beach. 1) In the near-field (<50 m downstream of the dye release location), the dye fully mixed throughout the water column after a few incident waves then continued to disperse in two dimensions, with both advection and diffusion processes being important. 2) In the far-field (>50 m downstream from the dye release location), the mass transport was dominated by advection. The distance to the far-field is much shorter in the alongshore on a steep beach compared with a dissipative beach. Estimates of cross-shore and alongshore diffusion coefficients (κ x , κ y ) were found to be similar in magnitude within the surfzone. Outside the surfzone in the far-field, the results suggest that the mixing processes are independent of those inside the surfzone. The mixing and transport of material observed on this steep beach are found to be analogous to that previously measured on dissipative beaches, however the diffusion coefficients within and outside the surfzone were found to be smaller on this steep beach.","Diffusion; Dispersion; Dye; Mass transport; Steep beach; Surfzone","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2019-09-23","","","Environmental Fluid Mechanics","","",""
"uuid:cfd445c2-91aa-45da-8476-ec33544bd9d9","http://resolver.tudelft.nl/uuid:cfd445c2-91aa-45da-8476-ec33544bd9d9","Tidal wave propagation along The Mekong deltaic coast","Phan, M.H. (TU Delft Coastal Engineering; Ministry of Agriculture and Rural Development); Ye, Qinghua (Deltares); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Stive, M.J.F. (TU Delft Coastal Engineering)","","2019","A two-dimensional, barotropic numerical model was employed to investigate the dynamics of tidal wave propagation in the South China Sea with a particular interest for its characteristics along the Mekong deltaic coast. The study indicates that tidal waves propagate from the Pacific Ocean into the South China Sea mainly through the Luzon Strait (LS), where the K 1 diurnal tide dominates due to a quarter wavelength resonance in this semi-enclosed basin, and that the incoming tidal waves from the Celebes open boundary play a more important role than those from the Andaman and Flores open boundaries. Previous studies have not explained why both adjacent seas including the South China Sea and the Gulf of Thailand are dominated by a diurnal tide, while a semidiurnal tide dominates along the eastern Mekong deltaic coast. By means of Green's law, continental shelf tidal resonance theory and standing wave theory, this study clarifies that the large amplified M 2 semidiurnal amplitude leading to a prevailing mixed semidiurnal tide is caused not only by the shoaling effect and the continental shelf oscillation resonance phenomenon but also by the position on the standing wave anti-node line. Moreover, the finding of radial tidal currents occurring along the southern Mekong estuarine coast has not been revealed in earlier studies. Based on a number of numerical, geometrically schematised experiments, we suggest that the interaction between the large amplified amplitude near the shoreline associated with the adjacent low amplitude band system, causing convex hydraulic gradients of tidal amplitude due to basin geometry as well as sloping topography, is the mechanism for developing these radial tidal current systems. The results reveal that wind monsoon climate could cause either damped or amplified tidal amplitudes around the Mekong deltaic coast of which approximately 2–3 cm is due to the changing atmospheric pressure, the tangential stress of wind over the water surface and wind enhanced bottom friction. Also, this study suggests that the tidal generating forces should be considered to achieve accurate model results depending on the geographical region of interest. Findings achieved from this study contribute to a deeper insight of tidal wave propagation from a deep ocean to a shallow flat basin similar to the South China Sea and its Mekong deltaic coast.","Mekong deltaic coast; Radial tidal currents; Resonance; Standing wave; Tidal wave propagation","en","journal article","","","","","","","","","","","Coastal Engineering","","",""
"uuid:9521b0ac-bb4d-4bfd-a7df-84acae5c95b8","http://resolver.tudelft.nl/uuid:9521b0ac-bb4d-4bfd-a7df-84acae5c95b8","Analysing decadal-scale crescentic bar dynamics using satellite imagery: A case study at Anmok beach, South Korea","Athanasiou, Panagiotis (Deltares); de Boer, W.P. (TU Delft Rivers, Ports, Waterways and Dredging Engineering; Deltares); Yoo, Jeseon (Korean Institute of Ocean Science and Technology (KIOST)); Ranasinghe, Roshanka (Deltares; IHE Delft Institute for Water Education; University of Twente); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2018","Understanding long-term sandbar dynamics can be crucial for informed coastal zone management, but is often hampered by data availability. To increase the number of sandbar observations available from bathymetric surveys, this study proposes and evaluates a method to manually extract the sandbar location using freely available satellite imagery for the case study of Anmok beach in South Korea. Validation of the satellite extracted sandbar locations against 9 in-situ measurements shows good agreement with errors well within the pixel resolution of the satellite imagery (i.e. 30 m for Landsat missions). The applicability of the method is constrained to locations where (1) the cross-shore crescentic length scales are larger than the image resolution, (2) frequent wave breaking and clouds are absent and (3) the water clarity is sufficient to enable the manual extraction of the sandbar crest line. Using the additional sandbar observations from the satellite imagery significantly increases the temporal extent and resolution of the dataset for Anmok beach. This allows the study of sandbar characteristics, dynamics and impacts of human interventions to an extent that would not have been possible without the satellite imagery. Within the study period 1990–2017 it is found that the sandbar maintains a persistent crescentic pattern that is only altered during prolonged and very intense storm conditions. The cumulative alongshore migration of the sandbars is investigated and found to be in the order of hundreds of meters over the 27 years study period. Comparing the sandbar characteristics prior and after the construction of Gangneung port shows that both the amplitudes and wavelengths of the sandbar crescents near the port have decreased after its construction.","Anmok beach; Crescentic sandbars; Human interventions; Sandbar dynamics; Satellite imagery","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2019-02-04","","","Rivers, Ports, Waterways and Dredging Engineering","","",""
"uuid:1837f76c-87af-40c6-9144-9c83165bf176","http://resolver.tudelft.nl/uuid:1837f76c-87af-40c6-9144-9c83165bf176","Wave Generation of Gravity-Driven Sediment Flows on a Predominantly Sandy Seabed","Flores, Raúl P. (University of Washington; Universidad Técnica Federico Santa María); Rijnsburger, S. (TU Delft Environmental Fluid Mechanics); Meirelles, Saulo (TU Delft Coastal Engineering); Horner-Devine, Alexander R. (University of Washington); Souza, Alejandro J. (CINVESTAV Unidad Merida); Pietrzak, J.D. (TU Delft Environmental Fluid Mechanics); Henriquez, M. (TU Delft Coastal Engineering); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2018","Wave-supported gravity flows (WSGFs) generate rates of sediment flux far exceeding other cross-shelf transport processes, contributing disproportionately to shelf morphology and net cross-shelf fluxes of sediment in many regions worldwide. However, the conditions deemed necessary for the formation of WSGF limit them to a narrow set of shelf conditions; they have been observed exclusively in regions where the seabed consists of very fine-grained sediment and typically co-occur with nearby river flood events. Here we document the occurrence of a WSGF event on a predominantly sandy seabed and in the absence of a preceding river flood. Our measurements confirm that the dynamics are governed by the friction-buoyancy balance observed in other WSGF and that WSGF can form in mixed grain-size environments and transport high concentrations of sand. The occurrence of WSGF on a predominantly sandy seabed suggests that they may occur under a much wider range of conditions and, given the global prevalence of sandy shelves, they may be a more frequent and more ubiquitous feature of shelf dynamics than previously thought.","cross-shelf transport; marine gravity-driven flows; sandy seabed; sediment transport; wave-supported gravity flows","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:24795a43-8fcd-408f-bd28-e221b16a0349","http://resolver.tudelft.nl/uuid:24795a43-8fcd-408f-bd28-e221b16a0349","Coastal protection by a small scale river plume against oil spills in the Northern Gulf of Mexico","Kuitenbrouwer, D. (TU Delft QN/Afdelingsbureau); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); MacMahan, Jamie (Naval Post Graduate School of Engineering and Applied Sciences); Roth, Mathias K. (Naval Post Graduate School of Engineering and Applied Sciences)","","2018","The Deepwater Horizon oil spill damaged some beaches along the Northern Gulf of Mexico (NGoMex) coast more than others, possibly related to the presence of natural protection mechanisms. In order to optimize future mitigation efforts to protect the coast, these mechanisms should be understood. The NGoMex coast is characterized by relatively long stretches of sandy beach interrupted by tidal inlets creating ebb-tidal river plumes featuring frontal zones that may act as transport barriers. This research investigates to what extent these plumes are capable of protecting the adjacent coast. This is done by means of a combination of a 3D Eulerian flow model and a Lagrangian particle model to track oil pathways and visualize Lagrangian Coherent Structures located at the plume front. The models are verified with measurements from a field experiment adjacent to Destin Inlet, Florida. The effects of wind, tidal range and river discharge on the oil fate are discussed. It was found that wind is the dominant parameter. Offshore wind prevents oil from beaching. During onshore winds, oil is pushed to shore, but near the inlet the plume is effective in reducing the amount of oil washing ashore during the ebbing tide. In general, the plume redistributes the oil but is not capable of preventing oil from beaching. For strong winds, the influence of the plume is reduced.","Coastal barriers; Inner shelf; Oil spill; River plume; Surface material transport","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2018-11-12","","","QN/Afdelingsbureau","","",""
"uuid:33c358c2-e9c7-4661-a5c6-2840fd9e1c14","http://resolver.tudelft.nl/uuid:33c358c2-e9c7-4661-a5c6-2840fd9e1c14","Mechanisms of cross-shore transport and spatial variability of phytoplankton on a rip-channeled beach","Fujimura, Atsushi G. (University of Guam); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Paris, Claire B. (Rosenstiel School of Marine and Atmospheric Science); Shanks, Alan L. (University of Oregon); MacMahan, Jamie H. (Naval Post Graduate School of Engineering and Applied Sciences); Morgan, Steven G. (Davis)","","2018","We investigated whether cross-shore distributions of coastal phytoplankton to the surf zone are controlled by hydrodynamics and their biological characteristics. Data from a rip-channeled beach indicate that concentrations of phytoplankton are higher in the surf zone than offshore. To examine how phytoplankton is transported toward the shore, we used a coupled biophysical model, comprised of a 3D physical model of coastal dynamics and an individual-based model (IBM) for tracking phytoplankton on the rip-channeled beach. Waves and wind in the biophysical model were parameterized by the conditions during the sampling period. Previous studies indicated that growth rates of phytoplankton can be enhanced by high turbulence, which might contribute to high phytoplankton concentration in the surf zone. Some numerical and laboratory works showed that turbulence can also increase the downward velocity of phytoplankton, which could be carried by onshore bottom currents and remain in the surf zone. Furthermore, we adapted the IBM with the theoretical model of diurnal vertical migration (DVM) for phytoplankton. The theoretical DVM works as follows: in the morning, phytoplankton cells adhere to air bubbles and stay at the surface and close to the shore in the daytime because onshore wind and surface current direction is usually onshore; in the late afternoon, the cells switch their attachment from air bubbles to sand grains and sink to the bottom where the water flow is normally onshore at night. Finally, depth-varying growth of phytoplankton was also incorporated into the DVM module. Simulations using neutral passive particles do not give the expected results of observed patterns. All tested mechanisms, i.e., wind- and wave-driven currents, rip-current circulation, turbulence-driven growth and sinking, DVM, and depth-varying growth, enhanced onshore phytoplankton migration and cell concentrations in the surf zone, indicating that both biological traits and physical factors can be essential to phytoplankton cross-shore transport and spatial variability. Our model is open to be modified and re-parameterized, followed by further analysis and validation, so that it can be more adequate for ecological assessment of coastal areas.","Cell growth; Cross-shore transport; Phytoplankton; Rip current; Surf zone; Turbulence; Vertical migration","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:cfbb6d08-2bb7-4831-b957-18587869ef34","http://resolver.tudelft.nl/uuid:cfbb6d08-2bb7-4831-b957-18587869ef34","Sensitivity of rip current forecasts to errors in remotely-sensed bathymetry","Radermacher, M. (TU Delft Coastal Engineering; WaveDroid); de Schipper, M.A. (TU Delft Coastal Engineering; Shore Monitoring & Research); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2018","Operational nearshore current forecasts based on numerical model simulations are gaining popularity as a measure to increase the safety of swimmers. Applying remotely-sensed bathymetry in these model simulations is often proposed in order to cope with rapidly changing nearshore bathymetry. Errors in the remotely-sensed bathymetry may negatively affect performance of the hydrodynamic model. Hence, this study aims to determine the sensitivity of modelled nearshore currents (with a strong focus on rip currents) to errors in remotely-sensed bathymetries. The errors in the remotely-sensed bathymetries (depth inversion algorithm applied to video stream) were quantified with a length scale-aware validation technique, providing useful insights in the contribution of pattern and amplitude errors to the total error throughout the analysis domain and over a range of bathymetric length scales. Subsequently, simulations with a nearshore hydrodynamic model were performed, using both in-situ and remotely-sensed bathymetries as an input. A comparison of predicted rip currents on either bathymetry yielded performance statistics for operational current forecasts on remotely-sensed bathymetries, taking the model with in-situ bathymetry as a reference. Linking these performance statistics back to the quantified errors in the remotely-sensed bathymetry finally revealed the relation between errors in flow and bathymetry. Of all rip currents generated on an in-situ bathymetry, 55% were reproduced on the remotely-sensed bathymetry, showing that models predicting nearshore currents on remotely-sensed bathymetry have predictive value. Positive rip current predictions were promoted significantly by accurate reproduction of the pattern and amplitude of nearshore bars at length scales between 200 and 400 m. In contrast to the length-scale aware validation technique applied here, commonly used domain-wide bulk error metrics lack important information about spatial variations in the quality of remotely-sensed bathymetry.","Depth inversion; Numerical modeling; Remote sensing; Rip currents; Sand motor; Swimmer safety","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2018-08-03","","","Coastal Engineering","","",""
"uuid:4cae77ec-45fd-4029-b8e5-5c3e68015b34","http://resolver.tudelft.nl/uuid:4cae77ec-45fd-4029-b8e5-5c3e68015b34","Effect of beach management policies on recreational water quality","Kelly, Elizabeth A. (University of Miami); Feng, Zhixuan (Woods Hole Oceanographic Institution; University of Miami); Gidley, Maribeth L. (University of Miami; NOAA Atlantic Oceanographic and Meteorological Laboratory); Sinigalliano, Christopher D. (NOAA Atlantic Oceanographic and Meteorological Laboratory; University of Miami); Kumar, Naresh (University of Miami); Donahue, Allison G. (University of Miami); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics; NSF NIEHS Oceans and Human Health Center; University of Miami); Solo-Gabriele, Helena M. (University of Miami)","","2018","When beach water monitoring programs identify poor water quality, the causes are frequently unknown. We hypothesize that management policies play an important role in the frequency of fecal indicator bacteria (FIB) exceedances (enterococci and fecal coliform) at recreational beaches. To test this hypothesis we implemented an innovative approach utilizing large amounts of monitoring data (n > 150,000 measurements per FIB) to determine associations between the frequency of contaminant exceedances and beach management practices. The large FIB database was augmented with results from a survey designed to assess management policies for 316 beaches throughout the state of Florida. The FIB and survey data were analyzed using t-tests, ANOVA, factor analysis, and linear regression. Results show that beach geomorphology (beach type) was highly associated with exceedance of regulatory standards. Low enterococci exceedances were associated with open coast beaches (n = 211) that have sparse human densities, no homeless populations, low densities of dogs and birds, bird management policies, low densities of seaweed, beach renourishment, charge access fees, employ lifeguards, without nearby marinas, and those that manage storm water. Factor analysis and a linear regression confirmed beach type as the predominant factor with secondary influences from grooming activities (including seaweed densities and beach renourishment) and beach access (including charging fees, employing lifeguards, and without nearby marinas). Our results were observable primarily because of the very large public FIB database available for analyses; similar approaches can be adopted at other beaches. The findings of this research have important policy implications because the selected beach management practices that were associated with low levels of FIB can be implemented in other parts of the US and around the world to improve recreational beach water quality.","Beach management; Beach use; Enterococci; Fecal coliform; Fecal indicator bacteria; Water quality","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2018-08-22","","","Environmental Fluid Mechanics","","",""
"uuid:bca7efc4-0662-465f-87d6-0280e32aa75c","http://resolver.tudelft.nl/uuid:bca7efc4-0662-465f-87d6-0280e32aa75c","Behaviour of subtidal sandbars in response to nourishments","Radermacher, M. (TU Delft Coastal Engineering; WaveDroid); de Schipper, M.A. (TU Delft Coastal Engineering; Shore Monitoring & Research); Price, Timothy (Universiteit Utrecht); Huisman, B.J.A. (TU Delft Coastal Engineering; Deltares); Aarninkhof, S.G.J. (TU Delft Coastal Engineering); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2018","The behaviour of subtidal sandbars can be strongly influenced by the introduction of sand nourishments in the coastal system. This study focuses on the impact of nourishments on subtidal bar behaviour at spatio-temporal scales beyond a single nourishment project. It aims to determine the long-term behaviour of subtidal sandbars along an entire coastal cell, taking into account both the unnourished and nourished regime, and covering various types of nourishments. The analysis is based on over 50 years of sandbar evolution along the Delfland coast, a 17-km long coastal cell at the Dutch North Sea coastline protected by groynes and maintained with frequent sand nourishments. Observations reveal clearly different sandbar behaviour during the unnourished (first 20 years) and nourished periods of the dataset. Introduction of the first beach nourishments (nourished sand primarily placed at the subaerial beach) was found to stimulate sandbar development along previously unbarred sections of the coast. Shoreface nourishments (nourished sand placed at the seaward face of the pre-existing subtidal sandbar) tended to migrate shoreward rapidly at a rate of 20 to 60 m/year at this coast, thereby forcing the pre-existing sandbar to weld to the dry beach. An abrupt transition of sandbar dynamics was observed following a major nourishment operation (∼ 37.5 Mm3 of nourished sand) that covered the entire coastal cell. A new, shallow sandbar formed with a degree of alongshore variability that was unprecedented at the Delfland coast over the full study period. These results imply that individual nourishments can influence the formation and migration of individual sandbars, while continued nourishments can fundamentally change long-term sandbar dynamics along an entire coastal cell.","sand nourishment; nearshore sandbars; sand motor; alongshore variability","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2018-10-15","","","Coastal Engineering","","",""
"uuid:549794c9-ff18-4bff-b8a5-6c41eaed5f21","http://resolver.tudelft.nl/uuid:549794c9-ff18-4bff-b8a5-6c41eaed5f21","Cross-shore stratified tidal flow seaward of a mega-nourishment","Meirelles, Saulo (TU Delft Coastal Engineering); Henriquez, M. (TU Delft Coastal Engineering); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Luijendijk, Arjen (TU Delft Coastal Engineering; Deltares); Pietrzak, J.D. (TU Delft Environmental Fluid Mechanics); Horner-Devine, Alexander R. (University of Washington); Souza, Alejandro J. (National Oceanography Center); Stive, M.J.F. (TU Delft Coastal Engineering)","","2018","The Sand Engine is a 21.5 million m3 experimental mega-nourishment project that was built in 2011 along the Dutch coast. This intervention created a discontinuity in the previous straight sandy coastline, altering the local hydrodynamics in a region that is influenced by the buoyant plume generated by the Rhine River. This work investigates the response of the cross-shore stratified tidal flow to the coastal protrusion created by the Sand Engine emplacement by using a 13 h velocity and density survey. Observations document the development of strong baroclinic-induced cross-shore exchange currents dictated by the intrusion of the river plume fronts as well as the classic tidal straining which are found to extend further into the nearshore (from 12 to 6m depth), otherwise believed to be a mixed zone. Estimates of the centrifugal acceleration directly after construction of the Sand Engine showed that the curvature effects were approximately 2 times stronger, suggesting that the Sand Engine might have played a role in controlling the cross-shore exchange currents during the first three years after the completion of the nourishment. Presently, the curvature effects are minute.","Baroclinic forcing; Centrifugal acceleration; Cross-shore exchange currents; Sand Engine","en","journal article","","","","","","","","2019-12-22","","","Coastal Engineering","","",""
"uuid:51796f78-a6c4-4279-9c38-ba585d9e556b","http://resolver.tudelft.nl/uuid:51796f78-a6c4-4279-9c38-ba585d9e556b","Long-term bar dynamics using satellite imagery: A case study at Anmok beach, South Korea","Athanasiou, Panagiotis (University of Twente; Deltares); de Boer, W.P. (TU Delft Rivers, Ports, Waterways and Dredging Engineering; Deltares); Tonnon, Pieter Koen (Deltares); Yoo, Jeseon (Korean Institute of Ocean Science and Technology); de Schipper, M.A. (TU Delft Coastal Engineering); de Vries, S. (TU Delft Coastal Engineering); Ranasinghe, Roshanka (TU Delft Coastal Engineering; University of Twente; Deltares); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2018","Nearshore sandbar patterns can affect the hydrodynamics and, as a result, the beach morphodynamics in the nearshore zone. Hence, spatial and temporal variability in the sandbars can influence beach accretion and erosion. Understanding the variability of the sandbar system can therefore be crucial for informed coastal zone management. So far, the methods to study sandbar dynamics mainly include datasets of video observations or occasional bathymetric surveys. However, at most locations around the world, these types of data are not or only scarcely available. In this paper we present an alternative method to analyze long-term sandbar variability by means of freely available satellite imagery. These images are globally available since the 1980’s and, thus, have the potential to be applicable at any location in the world. Here, we will illustrate the methodology by means of a case study at Anmok beach at the South Korean East coast.","","en","journal article","","","","","","","","","","","Rivers, Ports, Waterways and Dredging Engineering","","",""
"uuid:b7da6e56-bc6d-4b3b-b816-6d324f244b92","http://resolver.tudelft.nl/uuid:b7da6e56-bc6d-4b3b-b816-6d324f244b92","Persistent Differences in Horizontal Gradients in Phytoplankton Concentration Maintained by Surf Zone Hydrodynamics","Shanks, Alan L. (University of Oregon); Morgan, Steven G. (University of California); MacMahan, Jamie (Naval Post Graduate School of Engineering and Applied Sciences); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Jarvis, Marley (University of Oregon); Brown, Jenna (Naval Post Graduate School of Engineering and Applied Sciences); Fujimura, Atsushi G. (Rosenstiel School of Marine and Atmospheric Science); Ziccarelli, Lisa (University of California); Griesemer, Chris D. (University of California)","","2018","Surf zones, regions of breaking waves, are at the interface between the shore and coastal ocean. Surf zone hydrodynamics may affect delivery of phytoplankton subsidies to the intertidal zone. Over a month of daily sampling at an intermediate surf zone with bathymetric rip currents and a reflective surf zone, we measured surf zone hydrodynamics and compared concentrations of coastal phytoplankton taxa in the surf zones to concentrations offshore. At the intermediate surf zone, ~80% of the variability in the concentration of coastal phytoplankton taxa within the surf zone was explained by their variation offshore; however, concentrations were much higher and lower than those offshore in samples from a bathymetric rip current and over the adjacent shoal, respectively. Hydrodynamics at this intermediate surf zone did not hinder the delivery of coastal phytoplankton to the surf zone, but the bathymetric rip current system appeared to redistribute phytoplankton concentrating them within eddies. At the reflective shore, we sampled surf zones at a beach and two adjacent rocky intertidal sites. Concentrations of typical coastal phytoplankton taxa were usually an order of magnitude or more lower than those offshore, even when offshore samples were collected just 20 m beyond the breakers. The phytoplankton assemblages inside and outside the surf zone often appeared to be disconnected. Surf zone hydrodynamics at the steep, reflective shore coupled with low phytoplankton concentrations in near-surface water appeared to limit delivery of phytoplankton subsidies to the surf zone. Surf zone hydrodynamics may be a key factor in the alongshore variation in phytoplankton subsidies to coastal communities.","Beach morphodynamics; Benthic pelagic coupling; Dissipative; Intermediate; Reflective; Rip current","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2022-02-02","","","Environmental Fluid Mechanics","","",""
"uuid:f83c0000-e209-48ff-9673-e8edeaf900cf","http://resolver.tudelft.nl/uuid:f83c0000-e209-48ff-9673-e8edeaf900cf","On the accuracy of automated shoreline detection derived from satellite imagery: A case study of the Sand Motor mega-scale nourishment","Hagenaars, Gerben (Deltares); de Vries, S. (TU Delft Coastal Engineering); Luijendijk, Arjen (TU Delft Coastal Engineering; Deltares); de Boer, W.P. (TU Delft Rivers, Ports, Waterways and Dredging Engineering; Deltares); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2018","Measured trends and variability in shoreline position are used by coastal managers, scientists and engineers to understand and monitor coastal systems. This paper presents a new and generic method for automated shoreline detection from the largely unexplored collection of publicly available satellite imagery. The position of the obtained Satellite Derived Shoreline (SDS) is tested for accuracy for 143 images against high resolution in-situ data along a coastal stretch near the Sand Motor, a well-documented mega-scale nourishment along the Dutch coast. In this assessment, we quantify the effects of potential inaccuracy drivers such as the presence of clouds and wave-induced foam. The overall aim of this study is to verify whether the SDS is suitable to study structural coastline trends for coastal engineering practice.
In the ideal case of a cloud free satellite image without the presence of waves, with limited morphological changes between the time of image acquisition and the date of the in-situ measurement, the accuracy of the SDS is with subpixel precision (smaller than 10–30 m, depending on the satellite mission) and depends on intertidal beach slope and image pixel resolution. For the highest resolution images we find an average offset of 1 m between the SDS position and the in-situ shoreline in the considered domain. The accuracy deteriorates in the presence of clouds and/or waves on the image, satellite sensor corrections and georeferencing errors. The case study showed that especially the presence of clouds can lead to a considerable seaward offset of the SDS of multiple pixels (e.g. order 200 m). Wave-induced foam results in seaward offsets in the order of 40 m.
These effects can largely be overcome by creating composite images, which results in a continuous dataset with subpixel precision (10–30 m, depending on the satellite mission). This implies that structural trends can be detected for coastlines that have changed with at least the pixel resolution within the considered timespan.
Given the accuracy of composite images along the Sand Motor in combination with the worldwide availability of public satellite imagery covering the last decades, this technique can potentially be applied at other locations with large (structural) coastline trends.
For this purpose, fine material, dredged in the Port of Harlingen, is used to increase the bed level of the intertidal flats at North-East of the harbour. The sediment is not disposed directly on the mudflat but at the North-East edge of the Kimstergat Channel (Figure1b). The strategy is based on the presumption that the flood dominant system results in an extra net sediment transport onto the Koehool Mudflat (Figure1b). The imposed higher mud supply will gradually feed the mudflat (hence the name of the project: The Mud Motor) and is expected to accelerate the rate of bed level increase and, as consequence, the switch from a bare to a vegetated mudflat state.","","en","abstract","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:5561eccb-d11d-42dc-a277-41bcfd0e7956","http://resolver.tudelft.nl/uuid:5561eccb-d11d-42dc-a277-41bcfd0e7956","Wave attenuation by brushwood dams in a mud-mangrove coast","Gijón Mancheño, A. (TU Delft Environmental Fluid Mechanics); Tas, S.A.J. (TU Delft Environmental Fluid Mechanics); Herman, P.M.J. (TU Delft Environmental Fluid Mechanics; Deltares); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Uijttewaal, W.S.J. (TU Delft Environmental Fluid Mechanics); Winterwerp, J.C. (TU Delft Environmental Fluid Mechanics)","","2017","During recent decades, mangrove forests have experienced severe degradation due to unsustainable land use. Restoration of mangrove ecosystems requires the recovery of their habitat, considering ecology, hydrology, hydrodynamics, and sediment transport. In a first pilot in 2013, brushwood dams were built on the eroding coast of Demak, Indonesia, in order to emulate the function of mangrove roots and provide the physical conditions for natural colonization. However, at present there is little research on how soft structures affect the local hydrodynamics. The present study aims to improve the understanding of wave attenuation by permeable brushwood dams in Demak, combining field observations and hydrodynamic modelling using Delft3D. The findings of the study will be used to develop a landscape bio-morphodynamic model, which will be applied for planning future mangrove restoration efforts.","","en","abstract","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:df13ed15-6581-469b-87a6-84e66393c6e6","http://resolver.tudelft.nl/uuid:df13ed15-6581-469b-87a6-84e66393c6e6","A conceptual model for spatial Grain size variability on the surface of and within beaches","Gallagher, Edith (Franklin and Marshall College, Lancaster); Wadman, Heidi (US Army Corps of Engineers); McNinch, Jesse (US Army Corps of Engineers); Reniers, A.J.H.M. (TU Delft Hydraulic Engineering; TU Delft Environmental Fluid Mechanics); Koktas, Melike (Student TU Delft)","","2016","Grain size on the surface of natural beaches has been observed to vary spatially and temporally with morphology and wave energy. The stratigraphy of the beach at Duck, North Carolina, USA was examined using 36 vibracores (~1-1.5 m long) collected along a cross-shore beach profile. Cores show that beach sediments are finer (~0.3 mm) and more uniform high up on the beach. Lower on the beach, with more swash and wave action, the sand is reworked, segregated by size, and deposited in layers and patches. At the deepest measurement sites in the swash (~-1.4 to -1.6 m NAVD88), which are constantly being reworked by the energetic shore break, there is a thick layer (60-80 cm) of very coarse sediment (~2 mm). Examination of two large trenches showed that continuous layers of coarse and fine sands comprise beach stratigraphy. Thicker coarse layers in the trenches (above mean sea level) are likely owing to storm erosion and storm surge elevating the shore break and swash, which act to sort the sediment. Those layers are buried as water level retreats, accretion occurs and the beach recovers from the storm. Thinner coarse layers likely represent similar processes acting on smaller temporal scales.","Beach; Depth of disturbance; Grain size; Morphodynamics; Morphology; Sediment; Shore break; Storms; Stratigraphy; Swash","en","journal article","","","","","","Part of the special Issue ""Coastal Morphodynamics""","","","","Hydraulic Engineering","Environmental Fluid Mechanics","","",""
"uuid:cc24fc2b-0a91-415c-bef5-b128b2ba9dac","http://resolver.tudelft.nl/uuid:cc24fc2b-0a91-415c-bef5-b128b2ba9dac","Resonant near-surface inertial oscillations in the northeastern Gulf of Mexico","Gough, M.K.; Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); MacMahan, JH; Howden, SD","","2016","The inertial frequency is nearly diurnal at 30°N latitude which transects the northeastern Gulf of Mexico (NeGoM). At this latitude, near-surface inertial oscillations can amplify due to resonance with diurnal wind forcing. Diurnal oscillations have also been attributed to diurnal tidal forcing in this region. Because tidal forcing, wind forcing, and inertial oscillations are nearly diurnal, a unique series of comparative analyses are required to determine their relative influence on surface circulation. By comparing surface currents obtained by HF radar to predictions of the inertial response to wind forcing and barotropic tidal currents, it is found that diurnal oscillations in the NeGoM were predominantly due to wind-forced inertial oscillations in June 2010. The analyses provide a unique spatiotemporal perspective of inertial oscillations in the NeGoM where there is evidence of propagation, frequency and phase shifts, and amplitude variability. Because inertial oscillations mix the ocean differently than the tides, these results provide insight into how inertial oscillations potentially mixed oil from the Deepwater Horizon spill in June 2010. Near-diurnal oscillations during the winter were found to be predominantly due to tidal forcing when wind-driven inertial oscillations were diminished due to a presumably deeper mixed layer","","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:3e84d4aa-2f38-4895-b7a0-8bf8bc763e2e","http://resolver.tudelft.nl/uuid:3e84d4aa-2f38-4895-b7a0-8bf8bc763e2e","Statistical properties of the surface velocity field in the northern Gulf of Mexico sampled by GLAD drifters","Mariano, A.J. (University of Miami); Ryan, E.H.; Huntley, H.S. (University of Delaware); Laurindo, L.C. (University of Miami); Coelho, E. (CRME-STO); Ozgokmen, TM (University of Miami); Berta, M. (Istituto di Scienze Marine); Bogucki, D (Texas A and M University); Chen, S.S. (University of Miami); Curcic, M. (University of Miami); Drouin, K.L. (University of Miami); Gough, M (University of Miami); Haus, BK (University of Miami); Haza, A.C. (University of Miami); Hogan, P (Naval Research Laboratory); Iskandarani, M (University of Miami); Jacobs, G (Naval Research Laboratory); Kirwan Jr., A.D. (University of Delaware); Laxague, N (University of Miami); Lipphardt Jr., B. (University of Delaware); Magaldi, M.G. (Istituto di Scienze Marine; Texas A and M University); Novelli, G. (University of Miami); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics); Restrepo, J.M. (Oregon State University); Smith, C (University of Miami); Valle-Levinson, A. (University of Florida); Wei, M. (Naval Research Laboratory)","","2016","The Grand LAgrangian Deployment (GLAD) used multiscale sampling and GPS technology to observe time series of drifter positions with initial drifter separation of O(100 m) to O(10 km), and nominal 5 min sampling, during the summer and fall of 2012 in the northern Gulf of Mexico. Histograms of the velocity field and its statistical parameters are non-Gaussian; most are multimodal. The dominant periods for the surface velocity field are 1–2 days due to inertial oscillations, tides, and the sea breeze; 5–6 days due to wind forcing and submesoscale eddies; 9–10 days and two weeks or longer periods due to wind forcing and mesoscale variability, including the period of eddy rotation. The temporal e-folding scales of a fitted drifter velocity autocorrelation function are bimodal with time scales, 0.25–0.50 days and 0.9–1.4 days, and are the same order as the temporal e-folding scales of observed winds from nearby moored National Data Buoy Center stations. The Lagrangian integral time scales increase from coastal values of 8 h to offshore values of approximately 2 days with peak values of 3–4 days. The velocity variance is large, O(1)m2/s2, the surface velocity statistics are more anisotropic, and increased dispersion is observed at flow bifurcations. Horizontal diffusivity estimates are O(103)m2/s in coastal regions with weaker flow to O(105)m2/s in flow bifurcations, a strong jet, and during the passage of Hurricane Isaac. The Gulf of Mexico surface velocity statistics sampled by the GLAD drifters are a strong function of the feature sampled, topography, and wind forcing","","en","journal article","","","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:316f1b84-41ae-49a9-a479-8c50a2da24d5","http://resolver.tudelft.nl/uuid:316f1b84-41ae-49a9-a479-8c50a2da24d5","Modeling the effect of wave-vegetation interaction on wave setup","van Rooijen, A.A. (Deltares); McCall, R.T. (Deltares); van Thiel De Vries, J.S.M. (TU Delft Coastal Engineering; Royal Boskalis Westminster); van Dongeren, AR (Deltares); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics; Deltares); Roelvink, D. (Deltares; IHE Delft Institute for Water Education)","","2016","Aquatic vegetation in the coastal zone attenuates wave energy and reduces the risk of coastal hazards, e.g., flooding. Besides the attenuation of sea-swell waves, vegetation may also affect infragravity-band (IG) waves and wave setup. To date, knowledge on the effect of vegetation on IG waves and wave setup is lacking, while they are potentially important parameters for coastal risk assessment. In this study, the storm impact model XBeach is extended with formulations for attenuation of sea-swell and IG waves, and wave setup effects in two modes: the sea-swell wave phase-resolving (nonhydrostatic) and the phase-averaged (surfbeat) mode. In surfbeat mode, a wave shape model is implemented to capture the effect of nonlinear wave-vegetation interaction processes on wave setup. Both modeling modes are verified using data from two flume experiments with mimic vegetation and show good skill in computing the sea-swell and IG wave transformation, and wave setup. In surfbeat mode, the wave setup prediction greatly improves when using the wave shape model, while in nonhydrostatic mode (nonlinear) intrawave effects are directly accounted for. Subsequently, the model is used for a range of coastal geomorphological configurations by varying bed slope and vegetation extent. The results indicate that the effect of wave-vegetation interaction on wave setup may be relevant for a range of typical coastal geomorphological configurations (e.g., relatively steep to gentle slope coasts fronted by vegetation).","","en","journal article","","","","","","","","","","","Coastal Engineering","","",""
"uuid:d4bbee17-b99f-458f-9b19-9199a007e6f2","http://resolver.tudelft.nl/uuid:d4bbee17-b99f-458f-9b19-9199a007e6f2","Tidal flow separation at protruding beach nourishments","Radermacher, M. (TU Delft Coastal Engineering; WaveDroid); de Schipper, M.A. (TU Delft Coastal Engineering; Shore Monitoring & Research); Swinkels, Cilia M. (Deltares); MacMahan, Jamie (Naval Postgraduate School); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics; Deltares)","","2016","In recent years, the application of large-scale beach nourishments has been discussed, with the Sand Motor in the Netherlands as the first real-world example. Such protruding beach nourishments have an impact on tidal currents, potentially leading to tidal flow separation and the generation of tidal eddies of
length scales larger than the nourishment itself. The present study examines the characteristics of the tidal flow field around protruding beach nourishments under varying nourishment geometry and tidal conditions, based on extensive field observations and numerical flow simulations. Observations of the flow field around the Sand Motor, obtained with a ship-mounted current profiler and a set of fixed current profilers, show that a tidal eddy develops along the northern edge of the mega-nourishment every flood period. The eddy is generated around peak tidal flow and gradually gains size and strength, growing much
larger than the cross-shore dimension of the coastline perturbation. Based on a 3 week measurement period, it is shown that the intensity of the eddy modulates with the spring-neap tidal cycle. Depth-averaged tidal currents around coastline perturbations are simulated and compared to the field observations. The occurrence and behavior of tidal eddies is derived for a large set of simulations with varying nourishment size and shape. Results show that several different types of behavior exist, characterized by different combinations of the nourishment aspect ratio, the size of the nourishment relative to the tidal excursion length, and the influence of bed friction.","beach nourishment; flow separation; tidal flow; Sand Motor","en","journal article","","","","","","","","","","","Coastal Engineering","","",""
"uuid:600f4416-d924-4706-904b-cf50f3882543","http://resolver.tudelft.nl/uuid:600f4416-d924-4706-904b-cf50f3882543","Identification and classification of very low frequency waves on a coral reef flat","Gawehn, M. (Deltares); van Dongeren, AR (Deltares; University of Western Australia); van Rooijen, A.A. (Deltares); Storlazzi, C.D. (Pacific Coastal and Marine Science Center); Cheriton, O.M. (Pacific Coastal and Marine Science Center); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2016","Very low frequency (VLF, 0.001–0.005 Hz) waves are important drivers of flooding of low-lying coral reef-islands. In particular, VLF wave resonance is known to drive large wave runup and subsequent overwash. Using a 5 month data set of water levels and waves collected along a cross-reef transect on Roi-Namur Island in the Republic of the Marshall Islands, the observed VLF motions were categorized into four different classes: (1) resonant, (2) (nonresonant) standing, (3) progressive-growing, and (4) progressive-dissipative waves. Each VLF class is set by the reef flat water depth and, in the case of resonance, the incident-band offshore wave period. Using an improved method to identify VLF wave resonance, we find that VLF wave resonance caused prolonged (∼0.5–6.0 h), large-amplitude water surface oscillations at the inner reef flat ranging in wave height from 0.14 to 0.83 m. It was induced by relatively long-period, grouped, incident-band waves, and occurred under both storm and nonstorm conditions. Moreover, observed resonant VLF waves had nonlinear, bore-like wave shapes, which likely have a larger impact on the shoreline than regular, sinusoidal waveforms. As an alternative technique to the commonly used Fast Fourier Transformation, we propose the Hilbert-Huang Transformation that is more computationally expensive but can capture the wave shape more accurately. This research demonstrates that understanding VLF waves on reef flats is important for evaluating coastal flooding hazards","","en","journal article","","","","","","","","2017-03-31","","","Environmental Fluid Mechanics","","",""
"uuid:98a66b95-8fed-421a-9bfe-4ae978375dbe","http://resolver.tudelft.nl/uuid:98a66b95-8fed-421a-9bfe-4ae978375dbe","Modeling of wave attenuation by vegetation with XBeach","Van Rooijen, A.A.; Van Thiel de Vries, J.S.M.; McCall, R.T.; Van Dongeren, A.R.; Roelvink, J.A.; Reniers, A.J.H.M.","","2015","Over the past decades the effect of vegetation (e.g. kelp, mangroves, sea grass) on nearshore coastal processes has received more and more attention. In recent years several numerical wave models have been extended to include this effect. In the current study, the numerical storm impact model XBeach was extended with formulations found in literature for damping of short waves, infragravity waves, and mean flow. The model was then verified using a number of laboratory test cases. XBeach was well able to reproduce the damping effect of vegetation on waves, even though the amount of calibration done was limited. This work is considered as a first step only, and further model developments regarding vegetation implementation in XBeach are foreseen for the near future. Eventually, XBeach should be able to accurately take into account the effect of relatively complex vegetation species (e.g. mangroves) on the nearshore hydro- and morphodynamics in a computationally efficient way.","storm impact model; wave damping; kelp; mangroves; sea grass","en","conference paper","IAHR","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:acfebcdc-0364-4dc6-a914-99ffdd1440bb","http://resolver.tudelft.nl/uuid:acfebcdc-0364-4dc6-a914-99ffdd1440bb","Tilt current meter array: Field validation","Radermacher, M.; Thackeray, Z.H.; De Schipper, M.A.; Gordon, L.; Chrystal, C.; Leuci, R.; Reniers, A.J.H.M.","","2015","Measurements of nearshore currents can be performed using a range of existing measurement techniques. Although every technique has its specific benefits, capturing strong spatial gradients in a flow field with sufficiently high spatial resolution often proves to be difficult due to high costs or practical difficulties associated with these techniques. In this study, the use of an array of Tilt Current Meters is explored as a way of measuring these spatial gradients. Observed tilt angle and direction have a high correlation with flow velocity magnitude and direction measured with acoustic instruments. Furthermore, the capabilities of a dense spatial grid of Tilt Current Meters are demonstrated in a spatially variable flow field.","instrumentation; sand motor; measurements; flow; hydrodynamics","en","conference paper","IAHR","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:1ca82668-4f72-4894-b6dd-7b45e0fac841","http://resolver.tudelft.nl/uuid:1ca82668-4f72-4894-b6dd-7b45e0fac841","Field Observations of Surf Zone-Inner Shelf Exchange on a Rip-Channeled Beach","Brown, J.A.; MacMahan, J.H.; Reniers, A.J.H.M.; Thornton, E.B.","","2015","Cross-shore exchange between the surf zone and the inner shelf is investigated using Lagrangian and Eulerian field measurements of rip current flows on a rip-channeled beach in Sand City, California. Surface drifters released on the inner shelf during weak wind conditions moved seaward due to rip current pulses and then returned shoreward in an arcing pattern, reentering the surf zone over shoals. The cross-shore velocities of the seaward- and shoreward-moving drifters were approximately equal in magnitude and decreased as a function of distance offshore. The drifters carried seaward by the rip current had maximum cross-shore velocities as they exited the surf zone and then decelerated as they moved offshore. The drifters moving shoreward accelerated as they approached the surfzone boundary with maximum cross-shore velocities as they reentered the surf zone over shoals. It was found that Stokes drift was not solely responsible for the onshore transport across the surfzone boundary. The cross-shore diffusivity on the inner shelf was greatest during observations of locally contained cross-shore exchange. These field observations provide evidence that the cross-shore exchange between the surf zone and inner shelf on a rip-channeled beach is due to wave-driven rip current circulations and results in surface material being contained within the nearshore region.","circulation/dynamics; currents; Lagrangian circulation/transport","en","journal article","American Meteorological Society","","","","","","","2015-12-05","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:7f632aae-a9e9-4139-8674-7931bdc769b3","http://resolver.tudelft.nl/uuid:7f632aae-a9e9-4139-8674-7931bdc769b3","Transport of larvae and detritus across the surf zone of a steep reflective pocket beach","Shanks, A.L.; MacMahan, J.; Morgan, S.G.; Reniers, A.J.H.M.; Jarvis, M.; Brown, J.; Fujimura, A.; Griesemer, C.","","2015","Larvae of many intertidal species develop offshore and must cross the surf zone to complete their onshore migration to adult habitats. Depending on hydrodynamics, the surf zone may limit this migration, especially on reflective rocky shores. As a logistically tractable analog of a rocky shore environment, we carried out a comprehensive biological and physical study of the hydrodynamics of a steep reflective sandy beach. Holoplankton and precompetent larval invertebrates were much less abundant within the surf zone than offshore, and their concentrations inside and outside the surf zone were not significantly correlated, suggesting that they were not entering the surf zone. Persistent offshore flow throughout the water column at the outer edge of the surf zone may prevent these organisms from entering the surf zone. In contrast, the concentrations of detritus and a competent larval invertebrate (i.e. cyprids), while also not significantly correlated with concentrations offshore, were frequently more concentrated in the surf zone than offshore. Within the surf zone, the concentration of detritus was significantly correlated with concentrations of competent larval invertebrates (barnacles, gastropods, polychaetes, and bopyrid amphipod) and organisms that may be associated with detritus (amphipods and harpacticoid copepods). These concentrations were significantly negatively correlated with average daily wave height. We hypothesize that detritus and larvae enter the surf zone near the bottom during calm wave conditions by a process of near-bottom streaming. Near-bottom streaming is associated with all surf zones and may be a general mechanism for onshore transport of larvae close to the coast.","streaming; cyprids; competent larvae; precompetent larvae; detritus; reflective beach; cross-shore exchange","en","journal article","Inter-Research","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:51a3948d-8bb1-4a2f-bcc1-c4b0f29f6e47","http://resolver.tudelft.nl/uuid:51a3948d-8bb1-4a2f-bcc1-c4b0f29f6e47","Surfzone monitoring using rotary wing unmanned aerial vehicles","Brouwer, R.L.; De Schipper, M.A.; Rynne, P.F.; Graham, F.J.; Reniers, A.J.H.M.; Macmahan, J.H.","","2015","This study investigates the potential of rotary wing unmanned aerial vehicles (UAVs) to monitor the surfzone. This paper shows that these UAVs are extremely flexible surveying platforms that can gather nearcontinuous moderate spatial resolution and high temporal resolution imagery from a fixed position high above a study site. The rotary wing UAVs used in this study can fly for ;12 min with a mean loiter radius of 1–3.5m and a mean loiter error of 0.75–4.5 m. These numbers depend on the environmental conditions, flying style, battery type, and vehicle type. The images obtained from the UAVs, and in combination with surveyed ground control points (GCPs), can be georectified to a pixel resolution between 0.01 and 1m, and a reprojection error—that is, the difference between the surveyed GPS location of a GCP and the location of the GCP obtained from the georectified image—of O(1 m). The flexibility of rotary wing UAVs provides moderate spatial resolution and high temporal resolution imagery, which are highly suitable to quickly obtain surfzone and beach characteristics in response to storms or for day-to-day beach safety information, as well as scientific pursuits of surfzone kinematics on different spatial and temporal scales, and dispersion and advection estimates of pollutants.","","en","journal article","American Meteorological Society","","","","","","","2015-10-30","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:6f5a59bd-250a-432f-964b-4cdcc3b95e38","http://resolver.tudelft.nl/uuid:6f5a59bd-250a-432f-964b-4cdcc3b95e38","Scaling laws for the upper ocean temperature dissipation rate","Bogucki, D.J.; Huguenard, K.; Haus, B.K.; Özgökmen, T.M.; Reniers, A.J.H.M.; Laxague, N.J.M.","","2015","Our understanding of temperature dissipation rate ? within the upper ocean boundary layer, which is critical for climate forecasts, is very limited. Near-surface turbulence also affects dispersion of contaminants and biogeochemical tracers. Using high-resolution optical turbulence measurements, scaling laws for ? are investigated under forcing states where either the daytime heat flux or the wind stress forcing is dominant. We find that ? remains constant over 1.5 times the significant wave height, while over a layer below, ? decays based on the local surface forcing. When the heat flux is dominant, traditional scaling based on the Monin-Obukhov similarity theory remains valid; ? ? z?1. When the wind stress dominates, we observe the emergence of a new scaling, ? ? z?1/2, which is explained by invoking the effect of small-scale coherent structures on vertical heat transport. These results have implications for improved modeling of the ocean's heat and CO2 intake.","","en","journal article","American Geophysical Union","","","","","","","2015-08-10","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:db0cce45-0f49-40cc-8a3a-14870096c6f5","http://resolver.tudelft.nl/uuid:db0cce45-0f49-40cc-8a3a-14870096c6f5","The spatial-temporal variability of air-sea momentum fluxes observed at a tidal inlet","Ortiz-Suslow, D.G.; Haus, B.K.; Williams, N.J.; Laxague, N.J.M.; Reniers, A.J.H.M.; Graber, H.C.","","2015","Coastal waters are an aerodynamically unique environment that has been little explored from an air-sea interaction point of view. Consequently, most studies must assume that open ocean-derived parameterizations of the air-sea momentum flux are representative of the nearshore wind forcing. Observations made at the New River Inlet in North Carolina, during the Riverine and Estuarine Transport experiment (RIVET), were used to evaluate the suitability of wind speed-dependent, wind stress parameterizations in coastal waters. As part of the field campaign, a small, agile research vessel was deployed to make high-resolution wind velocity measurements in and around the tidal inlet. The eddy covariance method was employed to recover direct estimates of the 10 m neutral atmospheric drag coefficient from the three-dimensional winds. Observations of wind stress angle, near-surface currents, and heat flux were used to analyze the cross-shore variability of wind stress steering off the mean wind azimuth. In general, for onshore winds above 5 m/s, the drag coefficient was observed to be two and a half times the predicted open ocean value. Significant wind stress steering is observed within 2 km of the inlet mouth, which is observed to be correlated with the horizontal current shear. Other mechanisms such as the reduction in wave celerity or depth-limited breaking could also play a role. It was determined that outside the influence of these typical coastal processes, the open ocean parameterizations generally represent the wind stress field. The nearshore stress variability has significant implications for observations and simulations of coastal transport, circulation, mixing, and general surf-zone dynamics.","","en","journal article","American Geophysical Union","","","","","","","2015-08-05","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:cb7b35ea-9b5e-4053-a78d-b48924e63b8b","http://resolver.tudelft.nl/uuid:cb7b35ea-9b5e-4053-a78d-b48924e63b8b","Scale-selective Validation of Morphodynamic Models","Bosboom, J.; Reniers, A.J.H.M.","","2014","Although it is generally acknowledged that the practical predictability at smaller scales may be limited, output of high-resolution morphodynamic area models is mostly presented at the resolution of the computational grid. The so- presented fields typically are realistic looking, but not necessarily of similar quality at all spatial scales. Unfortunately, commonly used single-number validation measures do not provide the necessary guidance as to which scales in the output can be considered skilful. Also, differences in skill throughout the model domain cannot be discerned. Here, we present a new, scale-selective validation method for 2D morphological predictions that provides information on the variation of model skill with spatial scale and within the model domain. The employed skill score weighs how well the morphological structure and variability are simulated, while avoiding the double penalty effect by which point-wise accuracy metrics tend to reward the underestimation of variability. The method enables us to tailor model validation to the study objectives and scales of interest, establish the resolution at which results are ideally presented and target model development specifically at certain morphological scales.","morphodynamic modelling; model validation; spatial scales; local statistics; skill; ICCE 2014","en","conference paper","Coastal Engineering Research Council","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:2051be62-09ce-4f44-9650-f874f1502456","http://resolver.tudelft.nl/uuid:2051be62-09ce-4f44-9650-f874f1502456","Displacement-based error metrics for morphodynamic models","Bosboom, J.; Reniers, A.J.H.M.","","2014","The accuracy of morphological predictions is generally measured by an overall point-wise metric, such as the mean-squared difference between pairs of predicted and observed bed levels. Unfortunately, point-wise accuracy metrics tend to favour featureless predictions over predictions whose features are (slightly) misplaced. From the perspective of a coastal morphologist, this may lead to wrong decisions as to which of two predictions is better. In order to overcome this inherent limitation of point-wise metrics, we propose a new diagnostic tool for 2-D morphological predictions, which explicitly takes (dis)agreement in spatial patterns into account. Our approach is to formulate errors based on a smooth displacement field between predictions and observations that minimizes the point-wise error. We illustrate the advantages of this approach using a variety of morphological fields, generated with Delft3D, for an idealized case of a tidal inlet developing from an initially very schematized geometry. The quantification of model performance by the new diagnostic tool is found to better reflect the qualitative judgement of experts than traditional point-wise metrics do.","","en","journal article","European Geosciences Union","","","","","","","","Civil Engineering and Geosciences","Water Management","","","",""
"uuid:19e43807-c638-481f-a55b-0fe7361af63b","http://resolver.tudelft.nl/uuid:19e43807-c638-481f-a55b-0fe7361af63b","Displacement based error metric for morphodynamic models (abstract)","Bosboom, J.; Reniers, A.J.H.M.","","2013","The quality of a morphological prediction is often expressed by an overall grid-point based skill score based on the Mean Squared Error (MSE) between the predicted and observed bed levels (Sutherland et al., 2004). Although the MSE is a good measure of the overall error between model and observations, it tends to penalize rather than reward the model’s capability to provide information on features of interest such as scour holes, accumulation zones and migrating tidal channels; a feature that is predicted correctly in terms of timing and size but is (slightly) misplaced leads to a relatively large MSE as compared to a smoother forecast. This makes it difficult to demonstrate the skill of a high variability prediction (Anthes, 1983). Our aim is to overcome this inherent limitation of the MSE and other grid-point based error metrics. To that end, we introduce a new distance measure for 2D morphological change that explicitly takes (dis)agreement in spatial patterns into account.","","en","conference paper","IAHR","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:6daed133-e9e4-41ad-8028-fe7a830d28a7","http://resolver.tudelft.nl/uuid:6daed133-e9e4-41ad-8028-fe7a830d28a7","Observations and modeling of steep-beach grain-size variability","Reniers, A.J.H.M.; Gallagher, E.L.; MacMahan, J.H.; Brown, J.A.; Van Rooijen, A.A.; Van Thiel de Vries, J.S.M.; Van Prooijen, B.C.","","2013","Novel observations of surface grain-size distributions are used in combination with intra-wave modeling to examine the processes responsible for the sorting of sediment grains on a relatively steep beach (slope?=?1:7.5). The field observations of the mean grain size collected with a digital camera system at consecutive low and high tides for a 2 week period show significant temporal and spatial variation. This variation is reproduced by the modeling approach when the surf zone flow-circulation is relatively weak, showing coarse grain sizes at the location of the shore break and finer sediment onshore and offshore of the shore break. The model results suggest that grain size sorting is dominated by the wave-breaking-related suspended sediment transport which removes finer sediment from the shore break and transports it both on-shore and offshore. The transport capacity of wave-breaking-related suspended sediment is controlled by the sediment response time scale in the advection-diffusion equation, where small (large) values promote onshore (offshore) transport. Comparisons with the observed beach profile evolution suggest a relatively short time scale for the suspended sediment response which could be explained by the vigorous breaking of the waves at the shore break.","grain-size variability; swash; field observation; modeling","en","journal article","American Geophysical Union","","","","","","","2013-08-04","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:ccfb0f0a-268b-4cea-b8ec-f47a78be7ae8","http://resolver.tudelft.nl/uuid:ccfb0f0a-268b-4cea-b8ec-f47a78be7ae8","Morphological developments after a beach and shoreface nourishment at Vlugtenburg beach","De Schipper, M.A.; De Vries, S.; Ranasinghe, R.W.M.R.J.B.; Reniers, A.J.H.M.; Stive, M.J.F.","","2012","Typically a beach is out of equilibrium after a nourishment is installed. To observe how a nourished beach behaves on the timescale of storms a monitoring campaign was set up at Vlugtenburg beach after a nourishment in the spring of 2009. Here we show a sediment budget analysis of the first 2.5 years for a coastal domain spanning 1750 m alongshore from -9 to +5 m NAP. To investigate the redistribution of nourished sand different sections of the profile are examined. Observations show that the initial response (first 6 to 12 months after construction) is large where the sediment eroded from the beach is transported offshore to form a subtidal bar. In the following period (until present) the losses in the domain are on the order of 40 m3 per m alongshore per year. These losses are concentrated in the profile around the waterline.","","en","conference paper","University of Twente","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:823bae6c-93df-47fc-8a4d-9483de9ab003","http://resolver.tudelft.nl/uuid:823bae6c-93df-47fc-8a4d-9483de9ab003","Vortex tubes in the wave bottom boundary layer","Henriquez, M.; Reniers, A.J.H.M.; Ruessink, B.G.; Stive, M.J.F.","","2012","The cause of sediment suspension events during flow reversal under waves in the nearshore is not well understood. Vortex tubes and horizontal pressure gradients have been suggested to be the cause of the suspension events. A medium sized wave flume experiment has been conducted to give insight in the hydrodynamics of the wave bottom boundary layer over a fixed single-barred profile. Flow measurements were made with PIV and the swirling strength of the velocity fields were analyzed. Around flow reversal vortex tubes were identified. The vortex tubes had similar size and swirling strength as vortices generated by vortex shedding over a rippled bed. Therefore, vortex tubes under waves in the nearshore could explain the sediment suspension events around flow reversal.","","en","conference paper","University of Twente","","","","","","","","Civil Engineering and Geosciences","Water Management","","","",""
"uuid:9ae8c759-79b1-4cf3-ad4c-a540e460bee5","http://resolver.tudelft.nl/uuid:9ae8c759-79b1-4cf3-ad4c-a540e460bee5","On the initiation of nearshore morphological rhythmicity","De Schipper, M.A.; Ranasinghe, R.W.M.R.J.B.; Reniers, A.J.H.M.; Stive, M.J.F.","","2010","Nearshore rhythmicity is often initiated in the period just after a storm where the subtidal bar is turned alongshore uniform. The initiation time as well as the length scales of the created rhythmicity varies from one storm period to another. Here we show that the post-storm wave conditions are related to the initiation of the morphological rhythmicity. Narrow-banded and long wave period, both proxies for swell waves, are often found to be present prior to the initiation of rhythmicity. Furthermore, numerical model computations illustrate that swell waves induce significantly larger wave group induced velocities on the bar. These findings imply that the arrival of swell waves can initiate and stimulate the nearshore morphological rhythmicity","rhythmicity,; nearshore sandbars; wave groups","en","conference paper","","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:116b4ac6-ffb2-4796-9eda-b2fc04fa8596","http://resolver.tudelft.nl/uuid:116b4ac6-ffb2-4796-9eda-b2fc04fa8596","Vortical surf zone velocity fluctuations with 0(10) min period","MacMahan, J.H.; Reniers, A.J.H.M.; Thornton, E.B.","","2010","Observations of velocity fluctuations with periods between about 4 and 30 min, thus longer than infragravity waves and referred to as very low frequency (VLF) surf zone motions, are described and compared with numerical simulations. The VLF motions discussed here exclude instabilities (generated by the wave-driven alongshore current velocity shear) that occur in the same frequency range by selecting cases with weak alongshore currents only. Numerical simulations are based on the linear shallow water equations including friction and forced by nonlinear difference-frequency interactions between incident sea and swell waves. The model is initialized with sea and swell frequency directional spectra observed seaward of the surf zone. Modeled and observed VLF velocity fluctuation magnitudes agree within a factor of 2; both increase approximately linearly with increasing incident wave height and rapidly decay seaward of the surf zone. Observed frequency-wave-number, f-ky, spectra of VLF velocity fluctuations, estimated with instrumented alongshore arrays, are energetic in a broad range of ky in the vortical band. Observed and modeled VLF pressure fluctuations are relatively weak. Still, the model momentum balance suggests that VLF pressure gradients are as important as the nonlinear wave group forcing by sea and swell in accelerating/decelerating the VLF velocities. Model calculations demonstrate that the VLF-f-ky response is a function of the modulations of short-wave forcing associated with the frequency directional distribution of the incident sea and swell spectra. This results in VLF motions which span the surf zone and have O(50–1000 m) alongshore scales with O(200–2000 s) time scales. Given the fact that modulations of short waves resulting from directionally spread incident waves are common during field conditions we expect VLFs to be ubiquitous.","surf zone; rip current","en","journal article","American Geophysical Union","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:8f05a032-d3d7-4041-95bb-2eaca53a282f","http://resolver.tudelft.nl/uuid:8f05a032-d3d7-4041-95bb-2eaca53a282f","Rip?current pulses tied to Lagrangian coherent structures","Reniers, A.J.H.M.; MacMahan, J.H.; Beron-Vera, F.J.; Olascoaga, M.J.","","2010","The trapping and ejection of surfzone floating material is examined by unveiling Lagrangian Coherent Structures (LCSs) hidden in the pulsating rip?current surface velocity field produced by a three?dimensional numerical model resolving wave?group induced Very Low Frequency motions (VLFs). LCSs explain the typically observed patchiness of flotsam within the surf zone and the streaky distribution outside of the surf zone. The ejection of surfzone material occurs when filament?like LCSs separate form the main rip?current circulation corresponding to a situation where eddies temporarily extend the rip current beyond the surf zone and subsequently detach. The LCSs support the idea that VLFs form the dominant exchange mechanism of surfzone floating material with the inner shelf.","Lagranian Coherent Structures; rip current pulses; surfzone exchange","en","journal article","American Geophysical Union","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:467f79fe-1bcc-4ab4-916b-24f0899bb185","http://resolver.tudelft.nl/uuid:467f79fe-1bcc-4ab4-916b-24f0899bb185","Surf zone diffusivity on a rip-channeled beach","Brown, J.; MacMahan, J.; Reniers, A.J.H.M.; Thornton, E.","","2009","Absolute and relative diffusivity are measured on a rip-channeled beach using 30 position-tracking drifters released in clusters (4–12 drifters) deployed on 7 days with different wave forcing and tidal elevations at Sand City, Monterey Bay, California. Diffusivity and dispersion were found to be larger on days with rip current flow patterns and larger waves. Rip currents cause material to diffuse quickly for t < 90 s in the cross shore (Kxx = 5.4–6.1 m2/s) before decreasing to an asymptotic oscillation (Kxx = 0.9–2.2 m2/s), while alongshore material diffusion is initially (t < 170 s) smaller than cross-shore diffusion and asymptotes at a larger value (Kyy = 2.8–3.8 m2/s). The cross- and alongshore absolute diffusivity modulate at ~300 s corresponding to the average circulation time for a rip current. Two-particle relative dispersion (Dp) grows like Dp2 ~ t4/3 and the relative diffusivity (Kp) is scale dependent, Kp ~ d0.2 (d is particle separation). Cluster relative diffusion (Ke) ranged from 1.0 to 4.5 m2/s and cluster relative dispersions (De) are significantly correlated with two-particle relative dispersions (DS) [R2 > 0.9]. Two independent methods are used to measure the small-scale turbulent diffusion contribution (kxy), which are found significantly correlated (R2 = 0.95) with each other and calculated surf zone wave breaking induced turbulent eddy viscosity. Here kxy is small relative to the total dispersion (Ke/kxy = 3–30), indicating that the shear flow is the primary mechanism responsible for dispersion in a rip current system.","rip current; diffusivity; surf zone","en","journal article","American Geophysical Union","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:f2b3996e-a252-4f53-a981-0489db89921d","http://resolver.tudelft.nl/uuid:f2b3996e-a252-4f53-a981-0489db89921d","Surf zone surface retention on a rip?channeled beach","Reniers, A.J.H.M.; MacMahan, J.H.; Thornton, E.B.; Stanton, T.P.; Henriquez, M.; Brown, J.W.; Brown, J.A.; Gallagher, E.","","2009","The retention of floating matter within the surf zone on a rip-channeled beach is examined with a combination of detailed field observations obtained during the Rip Current Experiment and a three-dimensional (3-D) wave and flow model. The acoustic Doppler current profiler–observed hourly vertical cross-shore velocity structure variability over a period of 3 days with normally incident swell is well reproduced by the computations, although the strong vertical attenuation of the subsurface rip current velocities at the most offshore location outside the surf zone in 4 m water depth is not well predicted. Corresponding mean alongshore velocities are less well predicted with errors on the order of 10 cm/s for the most offshore sensors. Model calculations of very low frequency motions (VLFs) with O(10) min timescales typically explain over 60% of the observed variability, both inside and outside of the surf zone. The model calculations also match the mean rip-current surface flow field inferred from GPS-equipped drifter trajectories. Seeding the surf zone with a large number of equally spaced virtual drifters, the computed instantaneous surface velocity fields are used to calculate the hourly drifter trajectories. Collecting the hourly drifter exits, good agreement with the observed surf zone retention is obtained provided that both Stokes drift and VLF motions are accounted for in the modeling of the computed drifter trajectories. Without Stokes drift, the estimated number of virtual drifter exits is O(80)%, almost an order of magnitude larger than the O(20)% of observed exits during the drifter deployments. Conversely, when excluding the VLF motions instead, the number of calculated drifter exits is less than 5%, thus significantly underestimating the number of observed exits.","surf zone; stokes drift; retention","en","journal article","American Geophysical Union","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:715d1cda-31d4-4987-87be-247cbb2d5529","http://resolver.tudelft.nl/uuid:715d1cda-31d4-4987-87be-247cbb2d5529","Surfing waves generated by a hull","De Schipper, M.A.; De Vries, S.; Henriquez, M.; Reniers, A.J.H.M.; De Koning Gans, H.J.; Labeur, R.J.; Stive, M.J.F.","","2009","In this paper a new wave pool concept is presented using ship hulls as wave generators. To evaluate the potential of such a concept a towing tank experiment is conducted to investigate ship wave generation in a confined space. In the towing tank experiment various hull sizes and velocities are examined to maximize the generated wave height. The laboratory data shows that when blocking of the cross section of the pool by the hull is large, the large return flow significantly influences the wave height. This is in contrast to the open water case where the return flow is much smaller and therefore is not incorporated in wave height predictions. Based on the results of the physical model tests an optimum hull size and velocity are derived to maximize the potential use for surfing and a preliminary design of the wave pool is proposed.","Wave generation; Wave current interaction; Ship waves; Surfing","en","conference paper","World Scientific Publishing","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:2f7472f0-2f7a-48ba-a4fa-7974bfdae63b","http://resolver.tudelft.nl/uuid:2f7472f0-2f7a-48ba-a4fa-7974bfdae63b","On the scaling of sediment transport in the nearshore","Henriquez, M.; Reniers, A.J.H.M.; Ruessink, B.G.; Stive, M.J.F.; Stanton, T.P.; Foster, D.L.","","2009","Scale relations are necessary to choose proper sediment for physical models. The use of lightweight artificial sediment makes it possible to preserve the Reynolds number, Shields number and relative settling velocity altogether. There is also the possibility to preserve the Shields number in combination with the Dean number which would be more suitable in the case of significant wave breaking. Both cases have significant scale effects. A physical model test showed that the scale relations are useful under restricted conditions.","nearshore physical model; scaling rules; scaling criteria; artificial sediment; lightweight sediment","en","conference paper","IAHR","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:6cf7903d-a615-4ba4-9ada-25e531a46051","http://resolver.tudelft.nl/uuid:6cf7903d-a615-4ba4-9ada-25e531a46051","Reducing uncertainty in prediction of dune erosion during extreme conditions","Den Heijer, C.; Reniers, A.J.H.M.; Van de Graaff, J.; Van Gelder, P.H.A.J.M.","","2008","Coastal dunes protect low lying coastal areas against the sea. Extreme waves and water levels during severe storms may cause breaching of the dunes. Consequently, serious damage due to flooding and direct wave attack could occur, resulting in loss of life and property. Proper coastal management implies that reinforcement measures will be taken if the actual safety level does not meet the agreed standard. In order to cope with small probabilities of failure, which are relevant for the Dutch dune coast, a proper safety assessment method is required. Various aspects, which are currently considered as relevant for dune erosion, are not included in the present safety assessment method. This study concerns (1) an approach to reduce the uncertainty in dune erosion prediction as well as (2) a probabilistic sensitivity analysis of various variables that are included in the current Dutch safety assessment method. The aim of the latter part is to get more insight in the influence of the stochastic characteristics of the various variables which are taken into account in the current method. The calculation values which are used for the actual safety assessment, in a semi-deterministic way, are based on a full probabilistic investigation. This full probabilistic investigation has been used as a reference for the present sensitivity analysis, in which all stochastic characteristics have been varied. Both the deterministic DUROS+ model, which is used in the current safety assessment method, as well as the process based DUROSTA model have been applied. Main conclusion is that for both DUROS+ and DUROSTA the stochastic characteristics for the water level and the grain size are the most important for the prediction of dune erosion.","dune erosion; probabilistic approach; uncertainty; extreme hydraulic conditions","en","conference paper","","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:02700f6f-29b6-42e5-98c7-647809586fe5","http://resolver.tudelft.nl/uuid:02700f6f-29b6-42e5-98c7-647809586fe5","Modeling cross-shore sandbar behavior on the timescale of weeks","Ruessink, B.G.; Kuriyama, Y.; Reniers, A.J.H.M.; Roelvink, J.A.; Walstra, D.J.R.","","2007","We compare predictions of a coupled, wave-averaged, cross-shore waves-currents-bathymetric evolution model to observations of onshore and offshore nearshore sandbar migration. The observations span a 10- and 44-day period with onshore/offshore bar migration at Duck, North Carolina, and at Hasaki, Kashima Coast, Japan, respectively, a 3.5-month period of onshore bar migration at Duck, and a 22-day period of offshore bar migration at Egmond, Netherlands. With best fit parameter values the modeled temporal evolution of the cross-shore bed profiles agrees well with the observations. Model skill, defined as 1 minus the ratio of prediction to no-change error variances, ranges from 0.50 at Egmond to 0.88 for the prolonged onshore bar migration at Duck. Localized (in time and space) reductions in model skill coincide with alongshore variations in the observed morphology. Consistent with earlier observations, simulated offshore bar migration takes place during storms when large waves break on the bar and is due to the feedback between waves, undertow, suspended sediment transport, and the sandbar. Simulated onshore bar migration is predicted for energetic, weakly to nonbreaking conditions and is due to the feedback between near-bed wave skewness, bedload transport, and the sandbar, with negligible to small effects of bound infragravity waves and near-bed streaming. Under small waves and conditions, when breaking and nonbreaking conditions alternate with the tide, the sandbar is predicted to remain stationary. The intersite differences in the optimum parameter values are, at least partly, induced by insensitivity to parameter variations, parameter interdependence, and errors in the offshore wave forcing.","nearshore; sandbars; numerical modeling","en","journal article","American Geophysical Union","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:59324aa4-f4ba-40ed-8212-1b49548b8ef8","http://resolver.tudelft.nl/uuid:59324aa4-f4ba-40ed-8212-1b49548b8ef8","Modeling of very low frequency motions during RIPEX","Reniers, A.J.H.M.; MacMahan, J.H.; Thornton, E.B.; Stanton, T.P.","","2007","Numerical computations are used to explain the presence of very low frequency motions (VLFs), with frequencies less than 0.004 Hz, in the rip current velocity signals observed during the Rip-current field Experiment (RIPEX) field experiment. Observations show that the VLF motions are most intense within the surfzone and then quickly taper off in the offshore direction. By comparing computed VLF intensity (URMS,vlf) distributions in both the cross-shore and alongshore direction with observations in a qualitative sense, the most important contributions to the VLF dynamics are established. VLF motions at neighboring rip-channels are seen to interact in the computations, with stronger surfzone intensity for increasing bathymetric variation. The intermittent forcing by spatially varying wave groups is essential in obtaining the correct URMS,vlf distribution in the cross-shore direction, suggesting this is the predominant mechanism responsible for the generation of the VLF motions observed during RIPEX. Computations also suggest that VLF motions can occasionally propagate offshore but are mostly confined to the surfzone corresponding to surfzone eddies. A quantitative comparison shows good correspondence between model computations and measurements of URMS,vlf with a model skill of O(0.7), with generally increased (decreased) URMS,vlf during mean low (high) water levels.","modeling VLFs; rip-currents; wave groups","en","journal article","American Geophysical Union","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:c94363aa-4505-485f-bf0e-9fabdd5907ae","http://resolver.tudelft.nl/uuid:c94363aa-4505-485f-bf0e-9fabdd5907ae","Incipient motion of coarse particles under regular shoaling waves","Terrile, E.; Reniers, A.J.H.M.; Stive, M.J.F.; Tromp, M.; Verhagen, H.J.","","2005","Incipient motion of coarse particles under regular shoaling waves is examined. Experiments are performed to investigate the effects of bed fluid acceleration on coarse particle stability. By varying wave height, wave period and water depth, combinations of similar peak orbital velocities and weak to strong intra-wave accelerations were created. The particles used in these experiments have two different sizes both of a centimeter order of- magnitude. The data confirm that acceleration is important for the initiation of motion, since combinations of similar orbital velocity and varying acceleration magnitude resulted in no motion, some motion and motion as acceleration increased. Qualitatively we found that initiation of motion occurs at or is very close to the maximum shear stress due to the combined effects of drag / lift and acceleration as introduced by Nielsen and Callaghan [Nielsen, P. and Callaghan, D.P. (2003), Shear stress and sediment transport calculations for swash zone modelling. Coastal Engineering, 47, pp. 347–354]. However, quantitatively their formulation does not lead to convincing discrimination between motion and nomotion. We expect this to be due to the assumption that the coefficients for drag / lift and acceleration in their formulation are taken equal and constant. From literature and from plotting our data against the Keulegan–Carpenter number we expect that these coefficients strongly vary due to flow separation effects. To arrive at a more convincing discrimination between motion and no-motion we introduce a new fluid acceleration descriptor for nonlinear shoaling waves. The combination of this descriptor with a Reynolds number Reg more clearly delineates the regions with particle motion and without particle motion and has the potential to serve as a descriptor of the incipient motion of coarse particles under nonlinear and skewed, regular waves.","incipient motion; skewed waves; wave acceleration; KC-number","en","journal article","Elsevier","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:b54e4876-3726-4c87-b578-e48304b334ce","http://resolver.tudelft.nl/uuid:b54e4876-3726-4c87-b578-e48304b334ce","Motion threshold of coarse particles under regular shoaling waves","Stive, M.J.F.; Terrile, E.; Reniers, A.J.H.M.; Verhagen, H.J.","","2005","Threshold of motion of coarse particles under regular shoaling waves is studied. Experiments were performed to investigate the effects of bed fluid acceleration on coarse particle stability. By varying wave height, wave period and water depth combinations of similar peak orbital velocities and weak to strong intra-wave accelerations were created. Qualitatively we found that initiation of motion occurs at or is very close to the maximum shear stress due to the combined effects of drag/lift and acceleration as introduced by Nielsen and Callaghan (2003). However, quantitatively their formulation does not lead to convincing discrimination between motion and no motion. We expect this to be due to the assumption that the coefficients for drag/lift and acceleration in their formulation are taken equal. From literature and from plotting our data against the Keulegan-Carpenter number we expect that the coefficients strongly vary caused by flow separation effects.","incipient particle motion; skewed waves; wave acceleration; KC-number; bed stability","en","conference paper","","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:5454b130-7ca5-4bbc-baf3-4f332fbd03aa","http://resolver.tudelft.nl/uuid:5454b130-7ca5-4bbc-baf3-4f332fbd03aa","Coarse particles' threshold of motion under shoaling waves","Stive, M.J.F.; Reniers, A.J.H.M.; Terrile, E.; Verhagen, H.J.","","2005","The threshold of motion of coarse particles under regular shoaling waves is studied. Experiments are performed to investigate the effects of bed fluid acceleration on coarse particle stability. By varying wave height, wave period and water depth, combinations of similar peak orbital velocities and weak to strong intra-wave accelerations were created. Qualitatively we found that initiation of motion occurs at or is very close to the maximum shear stress due to the combined effects of drag/lift and acceleration as introduced by Nielsen and Callaghan (2003). However, quantitatively their formulation does not lead to convincing discrimination between motion and no motion. We expect this to be due to the assumption that the coefficients for drag/lift and acceleration in their formulation are taken equal and constant. From literature and from plotting our data against the Keulegan-Carpenter number we expect that these coefficients strongly vary due to flow separation effects.","shields; bed shear stress; shoaling waves","en","conference paper","","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:61acf9eb-5ddb-4634-96ad-c10e4817b9c6","http://resolver.tudelft.nl/uuid:61acf9eb-5ddb-4634-96ad-c10e4817b9c6","Quantification of 2D subtidal bathymetry from video","Roelvink, J.A.; Aarninkhof, S.G.J.; Wijnberg, K.M.; Reniers, A.J.H.M.","","2003","","kustmorfologie; coastal morphology; beeldverwerking; image processing; data-assimilatie; data assimilation","en","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:bc19df9b-74b7-4687-9e43-718076f41aa4","http://resolver.tudelft.nl/uuid:bc19df9b-74b7-4687-9e43-718076f41aa4","Longshore current dynamics","Reniers, A.J.H.M.","Battjes, J.A. (promotor)","1999","","","en","doctoral thesis","","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:663d987d-0488-4591-9cf2-f9c570108af5","http://resolver.tudelft.nl/uuid:663d987d-0488-4591-9cf2-f9c570108af5","Onderzoek naar lange golven bij Petten (deel A en B)","Haas, P.C.A. de; Rijks, D.C.; Ruessink, G.; Roelvink, J.A.; Reniers, A.J.H.M.; Gent, M.R.A. van","","1999","","lange golven; long waves; meetmethoden; measuring methods; stromingsmodellen; flow models","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:40431520-1609-4c69-b9e0-083230ff1816","http://resolver.tudelft.nl/uuid:40431520-1609-4c69-b9e0-083230ff1816","Onderwateroeversuppletie Delfland: UNIBEST-TC berekeningen","Reniers, A.J.H.M.; Roelvink, J.A.","","1997","","morfodynamica; morphodynamics; computerprogramma's; software; bodemligging; bed level","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:1f5ae3bc-786e-40e9-ae4b-662efbe42140","http://resolver.tudelft.nl/uuid:1f5ae3bc-786e-40e9-ae4b-662efbe42140","Diagnostic studies NOURTEC: Comparison between Thorsminde and Terschelling shoreface nourishments","Reniers, A.J.H.M.; Roelvink, J.A.","","1996","","kustsuppletie; coastal nourishment; kusttransport; littoral transport; zandtransport; sand transport; kustlijnontwikkeling; coastline development; Nederland; Terschelling; Denmark","en","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:453d9ae7-c671-48fa-a280-a022181c856f","http://resolver.tudelft.nl/uuid:453d9ae7-c671-48fa-a280-a022181c856f","Yearly-averaged sand transport at the -20 and -8 NAP depth contours of the Jarkus profiles 14, 40, 76 and 103","Rijn, L.C. van; Reniers, A.J.H.M.; Zitman, T.J.; Ribberink, J.S.","","1995","","modelonderzoek; modelling; golfvoortplanting; wave propagation; zandtransportmodellen; sand transport models; sedimentverdeling; sediment distribution; kustmorfologie; coastal morphology; Nederland","en","report","Deltares (WL)","","","","","","","","","","","","",""