M.A. van der Lugt
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8 records found
1
Journal article
(2026)
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Marlies van der Lugt, Noémie Fritsch, Matthieu de Schipper, Ad Reniers, Meagan Wengrove, France Floc'h
Low-energy sandy beaches typically have a rippled bed, and the presence of bed forms can strongly affect net sediment transport rates under combined forcing of waves and currents. In case low-energetic forcing is combined with coarse sediment, bed load transport is an important mechanism to understand transport processes on such beaches. This study presents observations of ripple geometry and migration from a low-energy beach composed of coarse sediment ((Formula presented.) m) in the bed load transport regime. The concurrent hydrodynamics were monitored with free-stream point measurements of velocity and pressure, and with velocity profiles from 15 cm above the bed into the wave boundary layer. The bed was rippled with relic and orbital vortex ripples. Cross-shore bed load transport associated with ripple migration was highly intermittent and alternating in direction. A bed load sediment transport model forced with the measured free-stream velocity signal led to a consistent overprediction of offshore directed transport. Using the measured velocities excluding the mean cross-shore velocity, the model captured the correct direction of all but one observed instance of migration in our data set. Velocity profiles confirmed that mean free-stream velocity was not representative of the magnitude and at times the direction of the mean flow in the wave bottom boundary layer over a rippled bed. Phase coupling between sea-swell and infragravity frequencies in orbital velocity forcing proved essential to capture the cross-shore bed load direction.
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Low-energy sandy beaches typically have a rippled bed, and the presence of bed forms can strongly affect net sediment transport rates under combined forcing of waves and currents. In case low-energetic forcing is combined with coarse sediment, bed load transport is an important mechanism to understand transport processes on such beaches. This study presents observations of ripple geometry and migration from a low-energy beach composed of coarse sediment ((Formula presented.) m) in the bed load transport regime. The concurrent hydrodynamics were monitored with free-stream point measurements of velocity and pressure, and with velocity profiles from 15 cm above the bed into the wave boundary layer. The bed was rippled with relic and orbital vortex ripples. Cross-shore bed load transport associated with ripple migration was highly intermittent and alternating in direction. A bed load sediment transport model forced with the measured free-stream velocity signal led to a consistent overprediction of offshore directed transport. Using the measured velocities excluding the mean cross-shore velocity, the model captured the correct direction of all but one observed instance of migration in our data set. Velocity profiles confirmed that mean free-stream velocity was not representative of the magnitude and at times the direction of the mean flow in the wave bottom boundary layer over a rippled bed. Phase coupling between sea-swell and infragravity frequencies in orbital velocity forcing proved essential to capture the cross-shore bed load direction.
SnapWave
Fast, implicit wave transformation from offshore to nearshore
This paper presents an efficient, implicit, unstructured-grid wave propagation model, SnapWave (Roelvink, 2025), which provides a simple and fast way to predict nearshore wave conditions at specified locations, for coastline models such as ShorelineS, or wave fields and their forcing of flows, to be used in other models, such as Delft3D-FM, XBeach or SFINCS. We describe the numerical method and verify the correct implementation by comparing against analytical solutions for schematized cases. We then test the model application in four different coastal settings by propagating time series of ERA5 hourly wave conditions to observation points nearshore and through the surf zone. We conclude that the model is robust, easy to set up and fast, and can be applied on open coasts worldwide.
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This paper presents an efficient, implicit, unstructured-grid wave propagation model, SnapWave (Roelvink, 2025), which provides a simple and fast way to predict nearshore wave conditions at specified locations, for coastline models such as ShorelineS, or wave fields and their forcing of flows, to be used in other models, such as Delft3D-FM, XBeach or SFINCS. We describe the numerical method and verify the correct implementation by comparing against analytical solutions for schematized cases. We then test the model application in four different coastal settings by propagating time series of ERA5 hourly wave conditions to observation points nearshore and through the surf zone. We conclude that the model is robust, easy to set up and fast, and can be applied on open coasts worldwide.
Conference paper
(2024)
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R.A.J. Jaarsma, M. Daugharty, S.D. Kamminga, M.A. van der Lugt, M.A. de Schipper, S. Nylund
Monitoring suspended sediment concentration (SSC) can be challenging as direct sampling methods are labour intensive and indirect measurements based on optical or acoustic backscatter are sensitive to changes in particle properties. Regardless, using ADCP backscatter to predict SSC is promising because of the possibility to capture suspended sediment transport by combining with flow measurements. To reduce sensitivity of established backscatter-SSC relations to changing particle size, a methodology is proposed where acoustic particle radius is derived using multi-frequency backscatter measurements obtained with a Nortek Signature1000 ADCP equipped with a vertical beam echosounder. Considering acoustic particle radii in an adapted backscatter-SSC model shows promising improvement in correlations with water sample reference measurements compared to the traditional single frequency approach based on a field test. Follow-up assessment is required to overcome limitations in dataset sample size and to investigate further improvements of the method. Still, application of the method can significantly enhance capability of ADCPs predicting SSC and – since backscatter is recorded over depth in conjunction with flow measurements – the ability to monitor suspended sediment transport using a single instrument.
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Monitoring suspended sediment concentration (SSC) can be challenging as direct sampling methods are labour intensive and indirect measurements based on optical or acoustic backscatter are sensitive to changes in particle properties. Regardless, using ADCP backscatter to predict SSC is promising because of the possibility to capture suspended sediment transport by combining with flow measurements. To reduce sensitivity of established backscatter-SSC relations to changing particle size, a methodology is proposed where acoustic particle radius is derived using multi-frequency backscatter measurements obtained with a Nortek Signature1000 ADCP equipped with a vertical beam echosounder. Considering acoustic particle radii in an adapted backscatter-SSC model shows promising improvement in correlations with water sample reference measurements compared to the traditional single frequency approach based on a field test. Follow-up assessment is required to overcome limitations in dataset sample size and to investigate further improvements of the method. Still, application of the method can significantly enhance capability of ADCPs predicting SSC and – since backscatter is recorded over depth in conjunction with flow measurements – the ability to monitor suspended sediment transport using a single instrument.
Wave models are essential for coastal engineering applications, because the (nearshore) wave conditions are required for the design of coastal structures, important drivers of coastal floodings and coastal erosion. Various spectral wave models exist to model the wave propagation, wind growth and energy transfer within a spectrum (Booij, et al. 1996, Günther, et al., 1992). These models have been improved over the last years (e.g. Rogers et al., 2015) and are able to accurately be applied for various applications. As a consequence the wave models became rather slower in terms of computational time than faster. This constricts the use of state-of-the-art wave models in probablistic flooding forecasts or continental scale wave climate downscaling for forcing shoreline modelling. Both these types of applications demand ensemble mode simulations achieved running all simulations in parallel on a super computer. Given that uncertainties in forecasting outcomes are not only a result of model uncertainty but also forcing uncertainty (e.g. hurricane track, storm intensity), this study investigates two alternative approaches to modelling the spectral wave action balance. The first model aims to downscale climate models to the water depths and regions relevant for shoreline modelling. The second alternative model approach aims to provide input to continental scale probabilistic (hurricane-driven) wave forecasts.
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Wave models are essential for coastal engineering applications, because the (nearshore) wave conditions are required for the design of coastal structures, important drivers of coastal floodings and coastal erosion. Various spectral wave models exist to model the wave propagation, wind growth and energy transfer within a spectrum (Booij, et al. 1996, Günther, et al., 1992). These models have been improved over the last years (e.g. Rogers et al., 2015) and are able to accurately be applied for various applications. As a consequence the wave models became rather slower in terms of computational time than faster. This constricts the use of state-of-the-art wave models in probablistic flooding forecasts or continental scale wave climate downscaling for forcing shoreline modelling. Both these types of applications demand ensemble mode simulations achieved running all simulations in parallel on a super computer. Given that uncertainties in forecasting outcomes are not only a result of model uncertainty but also forcing uncertainty (e.g. hurricane track, storm intensity), this study investigates two alternative approaches to modelling the spectral wave action balance. The first model aims to downscale climate models to the water depths and regions relevant for shoreline modelling. The second alternative model approach aims to provide input to continental scale probabilistic (hurricane-driven) wave forecasts.
Wave nonlinearity plays an important role in cross-shore beach morphodynamics and is often parameterized in engineering-type morphodynamic models through a nonlinear relationship with the Ursell number. It is not evident that the relationship established in previous studies also holds for sheltered sites with fetch-limited seas as they are more prone to effects of local winds and currents, the waves are generally steeper, and the beaches are typically reflective. This study investigates near-bed orbital velocity nonlinearity from wave records collected at two sheltered beaches in The Netherlands and contrasts them to earlier observations made along the exposed, wave-dominated North Sea coast. Our observations at sheltered beaches show that the Ursell number has comparable skill in predicting wave nonlinearity as it has on previously studied exposed coasts. However, the orbital velocities at sheltered coasts are more asymmetric for the same Ursell number than on exposed coasts. When exposed coast data were examined for moments with comparable high-steepness waves, a similar effect on asymmetry was observed. In addition, following and opposing winds were found to have a clear relationship with total nonlinearity, while they did not affect the phase between skewness and asymmetry at the sheltered beaches. Refitting the free parameters of an Ursell-based predictor improved the bias for the asymmetry parameterization. Whether this has implications for modeling of the magnitude of wave-nonlinearity-driven sediment transport using engineering type models is strongly dependent on the sediment transport formulation used, as these formulations depend on additional calibration coefficients too.
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Wave nonlinearity plays an important role in cross-shore beach morphodynamics and is often parameterized in engineering-type morphodynamic models through a nonlinear relationship with the Ursell number. It is not evident that the relationship established in previous studies also holds for sheltered sites with fetch-limited seas as they are more prone to effects of local winds and currents, the waves are generally steeper, and the beaches are typically reflective. This study investigates near-bed orbital velocity nonlinearity from wave records collected at two sheltered beaches in The Netherlands and contrasts them to earlier observations made along the exposed, wave-dominated North Sea coast. Our observations at sheltered beaches show that the Ursell number has comparable skill in predicting wave nonlinearity as it has on previously studied exposed coasts. However, the orbital velocities at sheltered coasts are more asymmetric for the same Ursell number than on exposed coasts. When exposed coast data were examined for moments with comparable high-steepness waves, a similar effect on asymmetry was observed. In addition, following and opposing winds were found to have a clear relationship with total nonlinearity, while they did not affect the phase between skewness and asymmetry at the sheltered beaches. Refitting the free parameters of an Ursell-based predictor improved the bias for the asymmetry parameterization. Whether this has implications for modeling of the magnitude of wave-nonlinearity-driven sediment transport using engineering type models is strongly dependent on the sediment transport formulation used, as these formulations depend on additional calibration coefficients too.
Journal article
(2024)
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Marlies A. van der Lugt, Jorn W. Bosma, Matthieu A. de Schipper, Timothy D. Price, Marcel C. G. van Maarseveen, Pieter van der Gaag, Gerben Ruessink, Ad J.H.M. Reniers, Stefan G. J. Aarninkhof
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).
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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).
Modeling the Morphodynamics of Coastal Responses to Extreme Events
What Shape Are We In?
Review
(2022)
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Christopher R. Sherwood, Ap Van Dongeren, Marlies van der Lugt, Jay Veeramony, John C Warner, James Doyle, Christie A. Hegermiller, Tian-Jian Hsu, Tarandeep S. Kalra, Maitane Olabarrieta, Allison M. Penko, Yashar Rafati, Dano Roelvink
This review focuses on recent advances in process-based numerical models of the impact of extreme storms on sandy coasts. Driven by larger-scale models of meteorology and hydrodynamics, these models simulate morphodynamics across the Sallenger storm-impact scale, including swash,collision, overwash, and inundation. Models are becoming both wider (as more processes are added) and deeper (as detailed physics replaces earlier parameterizations). Algorithms for wave-induced flows and sediment transport under shoaling waves are among the recent developments. Community and open-source models have become the norm. Observations of initial conditions (topography, land cover, and sediment characteristics) have become more detailed, and improvements in tropical cyclone and wave models provide forcing (winds, waves, surge, and upland flow) that is better resolved and more accurate, yielding commensurate improvements in model skill. We foresee that future storm-impact models will increasingly resolve individual waves, apply data assimilation, and be used in ensemble modeling modes to predict uncertainties.
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This review focuses on recent advances in process-based numerical models of the impact of extreme storms on sandy coasts. Driven by larger-scale models of meteorology and hydrodynamics, these models simulate morphodynamics across the Sallenger storm-impact scale, including swash,collision, overwash, and inundation. Models are becoming both wider (as more processes are added) and deeper (as detailed physics replaces earlier parameterizations). Algorithms for wave-induced flows and sediment transport under shoaling waves are among the recent developments. Community and open-source models have become the norm. Observations of initial conditions (topography, land cover, and sediment characteristics) have become more detailed, and improvements in tropical cyclone and wave models provide forcing (winds, waves, surge, and upland flow) that is better resolved and more accurate, yielding commensurate improvements in model skill. We foresee that future storm-impact models will increasingly resolve individual waves, apply data assimilation, and be used in ensemble modeling modes to predict uncertainties.
Journal article
(2019)
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Marlies A. van der Lugt
The accurate prediction of a barrier island response to storms is challenging because of the complex interaction between hydro- and morphodynamic processes that changes at different stages during an event. Assessment of the predictive skill is further complicated because of uncertainty in the hydraulic forcing, initial conditions, and the parameterization of processes. To evaluate these uncertainties, we investigated the morphological change that occurred during two Atlantic hurricane events on two barrier islands at Matanzas (Florida) and Fire Island (New York) with differing topographies and forcing conditions.
We used the morphodynamic model XBeach with hydrodynamic forcing extracted from a regional coupled D-Flow FM/SWAN model. The XBeach model was initialized with a spatially varying roughness map derived from a land cover classification map generated with supervised conditional-random-field classification. The model was supplemented with a dynamic roughness module recognizing that, under extreme conditions, vegetation can be washed away or buried by sediment.
For the Fire Island case, the modeled spatial extent of roughness reduction as a proxy for vegetation removal during the storm was accurate. For both the Fire Island and Matanzas cases, the model predicted erosion and deposition volumes and dune-crest lowering well. The occurrence of breach formation was also predicted by the model, but the exact location of these breaches did not match observations. Variations of 10% in boundary conditions (surge, wave direction, significant wave height, and bay water levels) produced regime shifts in modeled barrier island response. These results not only stress the critical role of boundary conditions in morphodynamic model skill, but also show the limitations of single deterministic model runs in forecasting impact. ...
We used the morphodynamic model XBeach with hydrodynamic forcing extracted from a regional coupled D-Flow FM/SWAN model. The XBeach model was initialized with a spatially varying roughness map derived from a land cover classification map generated with supervised conditional-random-field classification. The model was supplemented with a dynamic roughness module recognizing that, under extreme conditions, vegetation can be washed away or buried by sediment.
For the Fire Island case, the modeled spatial extent of roughness reduction as a proxy for vegetation removal during the storm was accurate. For both the Fire Island and Matanzas cases, the model predicted erosion and deposition volumes and dune-crest lowering well. The occurrence of breach formation was also predicted by the model, but the exact location of these breaches did not match observations. Variations of 10% in boundary conditions (surge, wave direction, significant wave height, and bay water levels) produced regime shifts in modeled barrier island response. These results not only stress the critical role of boundary conditions in morphodynamic model skill, but also show the limitations of single deterministic model runs in forecasting impact. ...
The accurate prediction of a barrier island response to storms is challenging because of the complex interaction between hydro- and morphodynamic processes that changes at different stages during an event. Assessment of the predictive skill is further complicated because of uncertainty in the hydraulic forcing, initial conditions, and the parameterization of processes. To evaluate these uncertainties, we investigated the morphological change that occurred during two Atlantic hurricane events on two barrier islands at Matanzas (Florida) and Fire Island (New York) with differing topographies and forcing conditions.
We used the morphodynamic model XBeach with hydrodynamic forcing extracted from a regional coupled D-Flow FM/SWAN model. The XBeach model was initialized with a spatially varying roughness map derived from a land cover classification map generated with supervised conditional-random-field classification. The model was supplemented with a dynamic roughness module recognizing that, under extreme conditions, vegetation can be washed away or buried by sediment.
For the Fire Island case, the modeled spatial extent of roughness reduction as a proxy for vegetation removal during the storm was accurate. For both the Fire Island and Matanzas cases, the model predicted erosion and deposition volumes and dune-crest lowering well. The occurrence of breach formation was also predicted by the model, but the exact location of these breaches did not match observations. Variations of 10% in boundary conditions (surge, wave direction, significant wave height, and bay water levels) produced regime shifts in modeled barrier island response. These results not only stress the critical role of boundary conditions in morphodynamic model skill, but also show the limitations of single deterministic model runs in forecasting impact.
We used the morphodynamic model XBeach with hydrodynamic forcing extracted from a regional coupled D-Flow FM/SWAN model. The XBeach model was initialized with a spatially varying roughness map derived from a land cover classification map generated with supervised conditional-random-field classification. The model was supplemented with a dynamic roughness module recognizing that, under extreme conditions, vegetation can be washed away or buried by sediment.
For the Fire Island case, the modeled spatial extent of roughness reduction as a proxy for vegetation removal during the storm was accurate. For both the Fire Island and Matanzas cases, the model predicted erosion and deposition volumes and dune-crest lowering well. The occurrence of breach formation was also predicted by the model, but the exact location of these breaches did not match observations. Variations of 10% in boundary conditions (surge, wave direction, significant wave height, and bay water levels) produced regime shifts in modeled barrier island response. These results not only stress the critical role of boundary conditions in morphodynamic model skill, but also show the limitations of single deterministic model runs in forecasting impact.