"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:8452f24d-afb7-4d08-b9d9-7ad384821f4e","http://resolver.tudelft.nl/uuid:8452f24d-afb7-4d08-b9d9-7ad384821f4e","Beach representation in morphodynamic predictions: Coupling models to improve beach behavior applied to Anmok beach","Caichac Avilés, Daniel (TU Delft Civil Engineering and Geosciences; TU Delft Hydraulic Engineering)","Aarninkhof, Stefan (mentor); Luijendijk, Arjen (graduation committee); McCall, Robert (graduation committee); de Boer, Wiebe (graduation committee); Reyns, J (graduation committee); Delft University of Technology (degree granting institution)","2017","Numerical process-based morphodynamic models are widespread in coastal engineering practice and have become the new standard when it comes to assessing the impact of natural or man-made structures on coastal environments. The most common practice among engineers is to focus on a single spatial and time scale, which means either neglecting certain processes under the assumption that they will average out, or performing detailed simulations for short time-spans in order to optimize the normally limited computational resources. Despite the efforts from several authors, at the moment there is a lack of a clear methodology which would allow incorporating the relevant physical phenomena only when required, hence optimizing the computational effort.
The above leads to the main research objective of this thesis: to gain insight in what is the added value of coupling process based morphodynamic models, regarding the morphological impacts near the beach. For this purpose two models that were originally conceived to resolve different timescales are selected; XBeach as a storm model, and the new suite from Deltares, Delft3D-Flexible Mesh (D3D-FM) as a long-term morphodynamic model. The area selected as study site is Anmok beach, located at the east coast of South Korea. The coastal erosion at this location is not yet well understood (mainly due to human interventions and storms) plus the micro-tidal wave-dominated environment makes this location ideal for this study. Recent researches on this site have found that there is a delicate balance between the stormy and calm periods, where the high energy wave events are the main drivers of local morphology.
One of the main findings in this thesis is that the coupling of independently calibrated models does not necessarily provide better morphodynamic results than the results obtained by running each model separately. Including different processes such as infragravity waves or Eulerian mass transport (which enhances the offshore sediment transport in the surf zone) during highly energetic events tend to generate large supratidal beach erosion. However, the post-storm recovery mechanisms present in long-term morphodynamic models are not sufficient to bring the sediment back to the beach. Therefore, it is recommended to include all the relevant physical processes (storm erosion and post storm recovery mechanisms) when following a coupling approach in order to have a coherent morphodynamic balance. Furthermore, the coupling of models can play an important role in identifying which processes are missing or are not fully represented by the different modelling packages.
The erosive effect of cumulative storms was shown to be relevant in the short to medium term and might become a key parameter when defining, for instance, the worst case scenario regarding shoreline retreat. Despite the fact that uncoupled long-term morphodynamic models produce better average results in the case of Anmok beach, the implementation of a coupled scheme was proven to be important when the erosion due to cumulative storm effects cannot be neglected.
Among the advantages of using D3D-FM for this work is the implementation of the Basic Model Interface, which meant an important reduction in bookkeeping efforts and the possibility to seamlessly couple D3D-FM with XBeach. This procedure allowed for the incorporation of more complex phenomena (such as infragravity waves) with an acceptable increase in computational time.
A research version of Delft3D (D3D) with specialized sediment transport equations in the swash zone was tested in an attempt to enhance the post-storm recovery mechanisms. The results obtained are promising in the sense that the accretion of the shoreline and lower dry beach was reasonably enhanced, especially when considering all the limitations involved in modelling the morphodynamics of the swash zone with a stationary wave model. Another important conclusion is that these models were capable of depositing the sediments at the lower backshore at best. Hence, there is still the need of a mechanism/process capable of transporting the sediments farther upslope into the dry beach or dunes, such as aeolian transport.
The decision to undergo with a coupled or uncoupled approach depends on case-by-case basis. For current practice, it is recommended to develop a coupled simulation in the medium-term, where both storms and calm periods have significant effects and where the intra seasonal variation could be a parameter of interest. For short-term simulations, an uncoupled storm model (e.g. XBeach) is recommended as is the most accurate for such a time span. For long-term simulations, the general recommendation is to run an uncoupled long-term model such as D3D. In this case the storm erosion and post-storm recovery processes are expected to average out, being the long-term model the most suitable package to obtain average morphological results.
For future work it is recommended to add an aeolian process-based model and incorporate the swash zone sediment transport module into D3D-FM as this would move us one step closer towards the development of a fully coupled model where all the relevant processes (storm erosion, post storm recovery and aeolian transport) are included.
In this thesis, a preliminary study was performed into a more sustainable alternative for the planned Tongzhou Bay Port, in which a basic connection was made between engineering and ecological point of view. A hydro-morphodynamic numerical model was made available and further developed for the modelling of the governing processes in the development of the intertidal mudflats at Tongzhou Bay. The model showed satisfactory results with respect to observations and net flow and transport features were closer analyzed. The different ecosystem types at Tongzhou Bay were quantified with ecotope classification and further validated with satellite-tracked data of two endangered shorebird species. Based on this validation, high-value ecotopes were determined based on these species and was used as an indication for the performance of alternative port configurations with respect to ecology.
With a better understanding of the governing processes for the development of the intertidal mudflats and ecotopes, a series of alternative port designs were conceived through several design cycle iterations. Guiding principles were the preservation of high-value ecotopes, the enhancement of these area’s development and the potential area created for future port development by each variant. Results showed that by understanding natural transport and siltation patterns, not only could alternative port configurations lead to the preservation of existing high-value ecotopes, but a stronger development of these areas with respect to the natural development could be realized as well. The preliminary results of this thesis show the potential of more sustainable alternative port designs through the Building-with-Nature principle, in creating benefits for both economic and ecological development of Tongzhou Bay.","Building with Nature; Reclamation; port design; Ecology; Ecotope; Jiangsu; Shorebirds; Yellow Sea; Tongzhou Bay; East China Sea; Coast; Sediment transport; Numerical modeling; Delft3D","en","master thesis","","","","","","","","","","","","","","32.238035,121.468706"
"uuid:5596663f-1668-4de6-b47e-425d7cb8d82e","http://resolver.tudelft.nl/uuid:5596663f-1668-4de6-b47e-425d7cb8d82e","The influence of the Sand Engine on the sediment transports and budgets of the Delfland coast: Analysis of bi-monthly high-resolution coastal profiles","Roest, Bart (TU Delft Civil Engineering and Geosciences; TU Delft Hydraulic Engineering)","Aarninkhof, S.G.J. (mentor); de Vries, S. (mentor); de Schipper, M.A. (graduation committee); Tissier, M.F.S. (graduation committee); Delft University of Technology (degree granting institution)","2017","The Sand Engine is a new innovation in coastal protection, a mega feeder nourishment. This pilot project was constructed in 2011 along the Delfland coast, which is historically prone to erosion. Since its construction, the Sand Engine is intensively being monitored to track the morphological development.
The objective of this thesis is therefore to assess how the morphology of the Sand Engine is evolving over time and how this evolution contributes to the sediment budgets of the Delfland coast. In this thesis the first five years of morphological evolution of Sand Engine and its surroundings are investigated.
A data analysis is performed on bi-monthly bathymetry measurements, covering the first five years of morphodynamic evolution of the Sand Engine and the surrounding coastal cell. The high temporal and spatial resolution in both alongshore and cross-shore direction, provided the opportunity to perform research in great detail and precision.
Volume changes and sediment transports are successfully derived. Sediments are redistributed in both alongshore and cross-shore direction over the coastal cell. The accretive areas slowly extend alongshore while the erosive part of the Sand Engine remains in the same position. The Sand Engine has a positive net contribution to the sediment budget of 5.8km of coast after 5 years, which is an extension of 3.2km. 4.2Mm^3 of the initially nourished volume of 17.5Mm^3, has been redistributed after 5 years.
A Gaussian curve is fitted to several iso-lines of constant altitude to describe the plan-form adjustment of the Sand Engine at different altitudes. The Gaussian parameters are useful in accurately describing the spatio-temporal behaviour. Yet large differences in adjustment rates are found over the altitude. The decrease in cross-shore extent is fastest around 0m+NAP, and decreases to near zero at -8m+NAP.
Cross-shore profile behaviour is investigated by inspection of the temporal evolution of characteristic cross-sections in accretive and erosive locations along the Sand Engine. Erosive and accretive profiles behave considerably different. The profiles are adjusting rapidly and bed-level activity varies considerably over the altitude, with a maximum morphological activity in the intertidal zone, rapidly decreasing with increasing depth.
The results show that the Sand Engine spreads alongshore and feeds the adjacent coastal sections in the five years after construction. A mega feeder nourishment is therefore capable of supplying sediments to the adjacent coast.
The first year morphodynamic response was much stronger than in any subsequent year. The current results therefore give an improved view on the long-term development of the Sand Engine.","Sand Engine; Sand Motor; Zandmotor; Sediment transport; Sediment budget; Coastal Engineering; Coastal profile; data-driven; Morphodynamics; Morphology; Delfland","en","master thesis","","","","","","","","","","","","Civil Engineering | Hydraulic Engineering | Coastal Engineering","","52.0530530, 4.18420108"
"uuid:4d69f8c5-1481-4292-94f1-1bffe792ebc9","http://resolver.tudelft.nl/uuid:4d69f8c5-1481-4292-94f1-1bffe792ebc9","Morphological Response of the Dutch Sandy Coast to Accelerated Sea Level Rise: A process-based modelling approach using Delft3D, applied to the Delfland coast","Lambert, Ingrid (TU Delft Civil Engineering and Geosciences)","Aarninkhof, S.G.J. (mentor); Luijendijk, A.P. (mentor); de Winter, Renske (mentor); Storms, J.E.A. (mentor); Delft University of Technology (degree granting institution)","2019","Accelerated sea level rise (SLR) is predicted to have multiple adverse impacts on the coastal zone, aggravating phenomena such as coastal erosion on sandy coasts. For climate change adaptation planning and informing policy, morphodynamic changes occurring at coastlines are becoming increasingly important. In this study, a calibrated Delft3D model forced by real-time wave conditions, was applied to simulate and assess the morphological behaviour of the Delfland coast in response to accelerated SLR over a 30-year time period. The calibrated Delft3D model uses a novel acceleration technique called brute-force merged (BFM) proposed by Luijendijk et al. (2019), which enables the modelling of multi-decadal predictions, with significant gain in computational effort. An assumption of the study was that no nourishments take place, i.e. no additional sediment supply. The Sand Engine (Zand Motor in Dutch), currently located along this coast was also excluded from the model, thereby assuming a straight unnourished coastline. A selection of six SLR scenarios was simulated, including a no SLR scenario used as the reference case. The chosen scenarios covered the full bandwidth of accelerated SLR projections translated for the Dutch coast up to 2100, assuming increased mass loss from the Antarctic ice sheet, a hypothesis proposed by DeConto and Pollard (2016). These projections therefore exceed those presented in the IPCC AR5. Based on the recent literature, the SLR rates selected, ranging from 3 mm/year to 120 mm/year, are assumed plausible and useful for the modelling study. Model outputs that are assessed include erosion and sedimentation plots, and volume changes, particularly erosion volumes. Analysis shows that no major change to the general coastal system behaviour occurs due to accelerated SLR; erosive sections in the south remain erosive and accretive regions in the northern part remain accretive. This is influenced mainly by gradients in alongshore sediment transport and presence of structures. Erosion volumes increase with higher SLR rates, indicating an increase in erosion rate due to accelerated SLR. Volume changes were calculated in different alongshore sections and in different depth/elevation zones in the cross-shore direction in order to identify regions more vulnerable to accelerated SLR. It is determined that the southern section is most impacted by SLR causing increased erosion, particularly in the subtidal zone. Processes driving the observations and trends are discussed in the study. With significant SLR, dune erosion also occurs due to water levels and waves being able to reach higher elevations. The dunes along the Delfland coast are the primary sea defence which protects the hinterland from flooding, therefore it is critical to consider potential dune erosion due to accelerated SLR. Implications of the model study’s findings are briefly discussed, in the context of coastal maintenance policy and implementation of nourishments. Evaluating the added value of Delft3D as a coastal impact model is another objective of the study. Delft3D shows a number of benefits, including detailed analysis at multiple spatio-temporal scales. Another is the inclusion of transport processes in both alongshore and cross-shore directions, which is not the case for the Bruun Rule or 1-D coastline models. A limitation of Delft3D is that it does not include aeolian transport processes, and so dune growth cannot be simulated.","Sea level rise; Sandy coasts; Morphodynamics; Delft3D; Coastal erosion; Process-based modelling; Climate change; Sediment transport","en","master thesis","","","","","","","","","","","","Coastal and Marine Engineering and Management (CoMEM)","","52.018516, 4.148583"
"uuid:eca33737-226e-4a87-b2f0-b822aead036b","http://resolver.tudelft.nl/uuid:eca33737-226e-4a87-b2f0-b822aead036b","The sediment capture efficiency of a managed realignment polder","Hilgersom, Tijmen (TU Delft Civil Engineering & Geosciences)","Aarninkhof, S.G.J. (mentor); van Maren, D.S. (graduation committee); van Weerdenburg, R.J.A. (graduation committee); van Prooijen, Bram (graduation committee); Delft University of Technology (degree granting institution)","2023","The Ems Dollart estuary is facing high levels of turbidity, which hinders the growth of algae and impacts the entire ecosystem. In recent years, turbidity has increased here with 0.5 to 3% per year between 1990 and 2010, corresponding to a doubling of suspended sediment concentration (SSC) within 24 years for the upper bound of 3%. This trend is mainly attributed to a decrease in the amount of sediment sinks. The Ems-Dollart 2050 program aims to address this issue by exploring various solutions, aiming to extract one million tons of dry matter from the estuary per year. This study investigates the potential of creating additional sediment sinks by scaling up managed realignment polders. The aim of the research is:
To investigate the important factors of influence for sediment capturing efficiency in a managed realignment polder, to make the mud extraction from a turbid estuary as efficient as possible while creating new natural and agricultural value.
Using the Delft3D FM numerical model, the study focuses on two key factors that influence sediment capturing, namely the effects of the surface area and the effect of the tidal prism (i.e. the volume of water that flows into an area during a tidal cycle), with the goal of making sediment extraction from the turbid estuary as efficient as possible. The study finds that the general concept of using a managed realignment polder to extract sediment is viable. However, the calibration process using Polder Breebaart revealed that the model struggled to accurately replicate some of the accumulation patterns in the low-dynamic system in this polder. While the model seems more appropriate for the project area, significant uncertainty remains due to the sensitivity of the results to sediment properties and calibration parameters.
The study's results suggest that a smaller tidal range can result in a more uniform sediment distribution across the area. This can be achieved by implementing a submerged weir behind the open entrance to the area. An even distribution of sediment could enhance the natural values in the intertidal area, which is a key goal of the Ems-Dollart 2050 program. In addition, wind-generated waves appear to have a major influence on the distribution of sediment over the area. Due to the extra shear stresses, waves provide more resuspension, which transports the sediment further.
Furthermore, the study observes a significant accumulation of sediment in a side-basin near the entrance. The high sediment accumulation in this area, compared to adjacent areas without accumulation, may be attributed to local low energetic conditions. This finding has potential implications for raising agricultural land using transitional polders.
In conclusion, this study provides insights into the effectiveness of using managed realignment as a method for extracting sediment from a turbid estuary. While it highlights some important aspects and influences, it also underscores the need for further research to confirm the findings and reduce the uncertainty in the results. Nevertheless, the potential benefits for both natural and agricultural values make this an intriguing avenue for future exploration.","Managed realignment; Polder Breebaart; Eems Dollard; Morphodynamics; Sediment transport; Morphodynamic modelling; Delft3D FM; Suspended Sediment Concentration","en","master thesis","","","","","","","","","","","","Civil Engineering | Environmental Engineering","RestCoast","53.303093, 7.016838"
"uuid:e1d7356f-dad6-4839-8279-a818642c4a4a","http://resolver.tudelft.nl/uuid:e1d7356f-dad6-4839-8279-a818642c4a4a","Understanding the interactions between crescentic bars, human interventions and coastline dynamics at the East coast of South Korea","Athanasiou, Panos (TU Delft Civil Engineering and Geosciences; TU Delft Hydraulic Engineering)","Reniers, A.J.H.M. (mentor); Ranasinghe, R. (graduation committee); de Schipper, M.A. (graduation committee); de Vries, S. (graduation committee); Tonnon, PK (graduation committee); de Boer, WP (graduation committee); Delft University of Technology (degree granting institution)","2017","Crescentic sandbars are a commonly observed nearshore feature in coastal zones that strongly influence the surfzone circulations and are connected with the occurrence of rip currents. Furthermore, their spatial characteristics have been associated with the shoreline position in the form of shoreline perturbations, indicating morphological coupling between them and in turn affecting the beach width. As changes in the beach width affect coastal infrastructure and user functions such as recreation, understanding the bar dynamics is crucial for coastal zone management. The present work intends to improve this understanding by means of a case study at Anmok beach located at the South Korean East coast. Data analysis is used to estimate the long-term changes of the sandbar characteristics in time, under the influence of the ambient environmental conditions and human interventions. Additionally, this study investigates how to account for these features in modelling frameworks.
Available in-situ bathymetric surveys and high resolution aerial photographs are complemented with freely available satellite images in order to extract an estimate of the horizontal position of the sandbar crest line at Anmok beach. The introduction of satellite imagery observations dramatically increases both temporal coverage and frequency of the dataset resulting in 27 years of bar observations. The sandbar characteristics are found to change mainly in response to high wave energy events, while the initial sandbar position seems to be an important factor e.g. the closer the sandbar to the shore the more prone to changes it is. Furthermore, the results indicate that the alongshore migration of the sandbar features and the alongshore component of the wave energy flux show an agreement between their long-term (5-10 years) trends. This highlights the potential of the alongshore wave generated current to migrate the sandbar patterns in the alongshore direction. Moreover, the magnitude of the crescentic length and amplitude in an area 600-700m away from the port decreased after its construction.
The use of coastline models that assume alongshore uniform bathymetry can be questioned in cases of pronounced alongshore morphological variability. To this end, the impact of the alongshore variability of the sandbar on net annual sediment transports is investigated with the process based morel Delft3D for a selection of schematized bathymetries, created based on the natural variability of the sandbar at Anmok. It appears that for the symmetrical shaped crescentic sandbars, which are mostly present at Anmok beach, the influence of the alongshore variability on the net sediment transports is not large (~10%). The shoreline response to different sandbar configurations is investigated by computing alongshore incoming and outgoing sand volumes in cells specified close to the shoreline. It is found that the cross-shore distance between the sandbar and the shoreline is critical for the intensity of the erosion and accretion patterns formed at the coastline. Moreover, according to the predominant direction of the wave climate the alongshore location of these shoreline patterns can vary.
After highlighting the importance of the sandbar location for the beach width, an attempt to model the sandbar mean cross-shore location in response to the wave forcing is realized in pursuit of predictive capability for future changing wave conditions. As process based numerical models have shown limitations in producing any predictive skill, two empirical models selected from literature are used. The calibration and validation of the models is unsatisfactory, possibly connected with the spatial accuracy and varying temporal resolution of the dataset or the simplification of the models themselves.
From the present work, the use of satellite imagery for studying of long-terms sandbar dynamics and the derivation of its characteristics is proven to be quite promising. It allowed us to increase the number of observations and hence, study the sandbar dynamics beyond the time-frame of in-situ surveys and aerial photography. Therefore, we could study the effects of human intervention on the long-term sandbar characteristics. This technique is believed to be useful for other sites with crescentic sandbars around the world.
A combination of different data sources (sediment samples, flow velocities, turbidity measurements and bathymetric data), together with a hydrodynamic model of the Western Scheldt and a morphodynamic model of Perkpolder are used to interpret the hydrodynamic and morphodynamic response of Perkpolder after the managed realignment.
Bathymetric data composed of LIDAR, multibeam and single-beam measurements shows three main developments in Perkpolder: (1) erosion of the frontal entrance area, the inlet and the seaward side of the creeks, (2) infilling of the creeks landward of the first bifurcation and (3) sedimentation on the intertidal area and even more sedimentation of the pond. By comparing the temporal evolution of the bed levels of the frontal entrance area with measured concentrations at the inlet of Perkpolder, it can be concluded that the frontal entrance area acted as a finite source of sediment that eroded quickly in the first years and increased sedimentation within Perkpolder during these years.
New realignment projects can profit from the research at Perkpolder. Bed shear stresses of the initial proposed layout of Perkpolder gives a clear indication if the creeks are setup correctly. Furthermore, an estimate of the initial sedimentation can be based on the accretion rate of other intertidal areas within the estuary. Since realigned areas are often more sheltered and have a lower elevation, accretion rates may be higher. Moreover, not only the forcing of the estuary, but at the same time the availability of different sediment sources and the initial bathymetry shape the morphodynamic response of the realignment site. Therefore, it is recommended to measure the bathymetry for a sufficient long period (e.g. 10 years after the realignment) to get grip on the mechanisms shaping the morphodynamics at these areas.","Managed realignment; Morphodynamics; Hydrodynamics; Perkpolder; Sediment transport; Morphodynamic modelling; Hydrodynamic modelling; Data analysis; Suspended Sediment Concentration","en","master thesis","","","","","","","","","","","","Civil Engineering | Hydraulic Engineering","","51.391403, 4.023281"
"uuid:c1eb704e-6c56-4d1e-875b-1b0fbabbd5eb","http://resolver.tudelft.nl/uuid:c1eb704e-6c56-4d1e-875b-1b0fbabbd5eb","Rehabilitating mangroves with a sediment nourishment: An initial assessment using a schematised model","Bles, Matthijs (TU Delft Civil Engineering and Geosciences)","Aarninkhof, S.G.J. (mentor); van Eekelen, Erik (mentor); van Prooijen, Bram (graduation committee); van Wesenbeeck, B (graduation committee); Terry-Tyson, Rachel (mentor); Delft University of Technology (degree granting institution)","2022","Mangroves are productive ecosystems. Degradation of mangroves has been observed since the 1970s, due to a variety of reasons. Successful rehabilitation focuses on restoring conditions suitable for mangroves. Sediment availability has been shown to positively impact mangrove growth. Therefore, it can likely play a role in mangrove rehabilitation. This research aims to explore if the rehabilitation of coastal mangroves is possible using a sediment nourishment.
A process analysis is performed, to identify the processes driving sedimentation on a mangrove coast. This analysis uses a schematised, cross-shore, one-dimensional model, based on global data of mangrove coasts. Convex, linear and concave bottom profiles are used. The forcing on the coasts consists of three different wave heights, tidal ranges, and sea level rise rates. A homogeneous mangrove forest is present above mean sea level.
Sedimentation within the mangrove forest is caused by a combination of processes. Waves pick up the sediment, which is transported by the tide. Tidal asymmetry then drives the actual sedimentation in the forest. An increase in asymmetry results in increased sedimentation. Mangroves increase the flood dominance of slack water asymmetry, but also cause an ebb dominant peak flow velocity and duration asymmetry.
Dependent on the tidal range, the influence of mangroves on net sedimentation can either be null, negative or positive.
Sea level rise increases sedimentation within the mangrove, by enhancing slack water asymmetry.
The main tipping point identified is the gradient of the bed slope in cross-shore direction. If the slope becomes milder towards the shore, i.e. a convex coast, this value is negative. If the slope becomes steeper, which is the case for concave coasts, it is positive. The tipping point is when the slope does not change towards the shore. The gradient of the slope then is zero. The net sedimentation is considerably less for concave coasts than for convex coasts.
Sediment nourishments can increase sedimentation in the mangrove forest. Four nourishment designs were simulated, using the same model as for the process analysis. The designs varied in location and achieved depth across the coast.
Three design considerations for a successful sediment nourishment have been identified, which are firstly the obtained bed level by the nourishment, secondly the slope of the original bed, and thirdly the location of the nourishment.
First, the obtained bed level by the nourishment influences the quantity of sediment pick-up. Higher bed levels increase the sedimentation within the mangrove, by increasing sediment mobilisation rates.
Second, the slope of the original bed largely influences the feasibility of a nourishment. Due to mild bed slopes, the construction of a nourishment is difficult and large volumes for a nourishment are required.
Finally, the location of the suppletion should be close to the mangrove. If the nourishment is located far offshore, the sediment is not transported towards the mangrove. Rather, it then is transported away from the coast.
This thesis has shown the rehabilitation of mangroves using a sediment nourishment is possible.
Flume experiments were conducted to measure the influence of bivalve shells on the threshold of motion of sand grains and current-driven bed load transport. The sediment-shell bed composition was altered in both experiments by varying the volumetric percentage of shell content. The bed compositions consisted of two distinct bivalve shell species: Ensis leei (elongated) and Spisula subtruncata (rounded) bivalve shell species.
It is proposed that the presence of shells initially disrupts the flow, leading to an increase in turbulence intensities. As shell content increases, a second effect becomes increasingly prevalent, which is sediment stabilization. The smaller sediment grains are hidden from the flow by larger, more exposed shell valves and shell fragments. Consequently, a higher bed shear stress is needed to mobilize the sand grains. The relative importance of these processes varies depending on shell content, shell species, and the potential of the shell to enhance turbulence intensities. The elongated shape of the E. leei bivalve shell enhanced turbulence intensities significantly and thereby influencing the threshold for sand grain motion. Bed load transport rates are reduced with increasing shell content. Initially, at a shell content of 10%, the rates only decreased marginally compared to a situation without shells, and no clear difference between shell species was observed. At a shell content of 20%, bed load transport rates decreased further. Thus, when predicting sediment transport, considering the presence of shells alone is insufficient, and consideration of shell shape and size is crucial.","Sediment; Shells; Bivalve shells; Bed load transport; Flume; Experiment; Experimental research; Sediment transport; Threshold of motion; Transport predictor","en","master thesis","","","","","","","","2024-08-30","","","","Civil Engineering | Hydraulic Engineering | Coastal Engineering","",""
"uuid:72bc2e28-3b6a-4940-ab63-3c9d7a55e30a","http://resolver.tudelft.nl/uuid:72bc2e28-3b6a-4940-ab63-3c9d7a55e30a","A numerical assessment of land reclamation as a strategy for nearshore diamond mining","Anker, J.C.","Buxton, M.W.N. (mentor); Verhagen, H.J. (mentor); Stive, M.J.F. (mentor); Van der Wijk, M. (mentor)","2015","On the south-west coast of Namibia, diamonds were trapped during the Quaternary on bedrock platforms and in bedrock gullies. These were formed by differential erosion due to wave action. The diamonds originated from Kimberlite diamond pipes within the catchment area of the Orange River in South-Africa and Botswana. This river eroded the diamonds from the pipes and transported them over a distance up to 1000 km to the sea. Subsequent deposition resulted in the formation of placer deposits on the south-west coast of Namibia. These diamond deposits form the mineral reserve for the Southern Coastal Mine, operated by NAMDEB, which is the area of interest for this study. The currently used extraction strategy in the mine is based on the philosophy that the mining method must be selective and land-based. Conventional loading and hauling of overburden and bulk material is applied after which a final cleaning of the bedrock is done with vacuum cleaners. A seawall made out of sand protects the mine along the entire coastline against flooding. Overburden sand and tailings are constantly transported and dumped onto the beach to achieve land reclamation. This is referred to as the Sand-2-Sea program, developed to expand mining activity in a seaward direction. When enough land is accrued the sandy seawall, protecting the mining operation against flooding, is shifted seawards and new mining area is claimed. The coastal area is characterized by a highly energetic wave climate. This causes a high erosion rate of the sand nourishment along the coast. The strategic business plan of NAMDEB states that diamond extraction, using the current mining- and land reclamation method, must continue until 2031 reaching a maximum seaward distance of 545 m from the average high water line (Mean Sea Level (MSL) +2m) of 2014. It was hypothesized in this thesis that the feasibility limit of the current mining method is reached before this maximum distance is obtained. In addition, severe seawall erosion can occur during storm events. A storm in May 2015 was an example of this, causing seawall failure and flooding of an area with ongoing mining activity. This event is used as a case study in this thesis. The aim of this thesis was to indicate how far seawards the land reclamation strategy for diamond mining can be applied. In addition, research was conducted to define standards for a seawall to effectively protect a mining area against flooding.","XBeach; Placer deposit; Coastal modelling; Dune erosion; Sediment transport; SWAN; Namibia; Sperrgebiet; Diamond mining","en","master thesis","","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering and Resource Engineering","","Mining Engineering and Coastal Engineering","","-28.553691, 16.321566"
"uuid:17221490-06e9-4769-a23d-bbd3f6f2a731","http://resolver.tudelft.nl/uuid:17221490-06e9-4769-a23d-bbd3f6f2a731","The influence of vegetation on flow and transport mechanisms: An experimental study on sediment transport mechanisms in two parallel stretches of vegetated and non-vegetated bed","Lokin, Lieke (TU Delft Civil Engineering and Geosciences; TU Delft Hydraulic Engineering)","Uijttewaal, Wim (mentor); Sloff, Kees (mentor); Mosselman, Erik (mentor); Penning, W.E. (mentor); Delft University of Technology (degree granting institution)","2017","Vegetation on river banks and bars contribute to the stability of these morphological features; however, the exact processes that contribute to this stabilization are still subject to research. This study has looked into the flow phenomena at the streamwise interface between a vegetated and non-vegetated river bed. Flow velocities in vegetated flows are lower than in non-vegetated flows under otherwise similar conditions due to the increased drag by the plants. Therefore, a shear layer develops across the interface. Within this shear layer, Kelvin-Helmholz like vortices develop, inducing exchange of mass and momentum through the interface. These vortices are present in the water column, but their strength near the bed governs sediment transport mechanisms, which are the basis of morphological activity. The objective of this study was therefore: to obtain a better understanding of the coherent flow structures in the interface between vegetated and non-vegetated river beds and the effect of these structures on sediment transport mechanisms. This has been done in a series of flume experiments with a compound channel.","Vegetation; Flow measurements; Experiment; fluid dynamics; Sediment transport","en","master thesis","","","","","","","","","","","","","",""
"uuid:e6c74ee1-a795-419f-92b2-d023c2c6a050","http://resolver.tudelft.nl/uuid:e6c74ee1-a795-419f-92b2-d023c2c6a050","Numerical modeling of sediment transport over hydraulic structures","Vuik, V.","Van Balen, W. (mentor); Mosselman, E. (mentor); Schielen, R.M.J. (mentor); Uijttewaal, W.S.J. (mentor); De Vriend, H.J. (mentor)","2010","Hydraulic structures are present in the designs of different Room for the River projects in the Netherlands. Examples are longitudinal weirs, groins, summer dikes and weirs in the inlet of a side channel. Morphological simulations with Delft3D are frequently carried out to investigate the effect of such projects on for example hindrance for shipping and dredging costs. It is important that also the physical processes around hydraulic structures are correctly modeled in these situations. At the upstream slope of a hydraulic structure, the larger depth-averaged velocity causes an increased sediment transport capacity and increased actual bed shear stresses. The latter is reinforced by a change of the velocity distribution over the vertical with respect to uniform flow. Opposite, the gravity component along the slope results in a higher critical bed shear stress than in flat bottom conditions. At steep slopes, (partial) bed-load transport blockage could occur. Delft3D is meant to model flow phenomena of which the horizontal length and time scales are significantly larger than the vertical scales. Near hydraulic structures, this is generally not the case. These structures are parameterized as weirs in a depth-averaged Delft3D model in engineering practice. The only effect of these weirs is an additional energy loss in the momentum equation. The parameterization aims at representing the influence of the weirs on the flow at larger scales. The local flow around the structures (including turbulence, vertical velocity components and actual shear stresses) is not correctly modeled. Moreover, there is no direct influence of the weir on sediment transport (like increased critical shear stresses and bed-load transport blockage). This inaccurate way of modeling could result in errors in the prediction of the morphological effects of hydraulic structures. The objectives of this study are: (1) Assessing the performance of the current way of Delft3D modeling of sediment transport around hydraulic structures in three-dimensional flows. (2) Making recommendations on the modeling of sediment transport around hydraulic structures in hydraulic engineering practice. The performance of Delft3D has been judged by comparing the results with the results of the numerical model FLUENT. FLUENT is an advanced flow modeling system, in which sediment transport can be studied by analyzing the trajectories of discrete particles. Firstly, some laboratory experiments describing flow and transport over structures have been modeled. In this way, the performance of both models has been investigated and mutually compared. The results of FLUENT gave confidence to use FLUENT as an instrument to judge the performance of Delft3D in modeling three-dimensional flow and transport over hydraulic structures. A three-dimensional flow situation has been designed, which resembles the flow over a longitudinal weir. In Delft3D, all bed-load transport and suspended-load transport that reaches the weir also passes the weir. In FLUENT, this is not the case. Suspended-load transport is distributed between the main channel and the zone behind the weir in the same ratio as the discharge. The distribution of bed-load transport strongly depends on the particle diameter. This difference shows that the parameterization of weirs in depth-averaged Delft3D models gives significant errors in the prediction of sediment transport over hydraulic structures, especially when bed-load transport is dominant. The transport magnitude can be reduced by increasing the bed level points near the weir to crest level. In this schematization, nearly all bed-load transport is blocked and suspended-load transport is reduced. A weir without increased bed level points overestimates the sediment transport over the structure. When the bed level points are increased until crest level of the weir, the sediment transport over the weir is underestimated. The sediment transport over the weir can be tuned by an increased bed level somewhere between zero and crest level. The distribution of sediment between the main channel (index 1) and the area behind the weir (index 2) can be described with a relation S2/S1 = C*Q2/Q1: The value of C as given by Delft3D can be judged with the following rules of thumb: (1) Suspended-load transport is distributed between the main channel and the zone behind the weir in the same ratio as the discharge, so C = 1. (2) For bed-load transport in three-dimensional situations with clearly oblique flow over the weir, the coefficient C can be related to the excess shear stress at the upstream slope, in which the actual and critical Shields parameter are adjusted for slope effects. (3) In situations where the flow is directed almost perpendicular to the crest of the structure, the conclusions of Lauchlan (2001) are recommended. Nearly all mobile sediment is transported over the structure in these situations. The coefficient C in Delft3D can be influenced by giving the bed level points near the weir the right height.","Hydraulic structures; Numerical modelling; Sediment transport; Delft3D; FLUENT; Morphology; Ruimte voor de Rivier; Room for the River; Computational Fluid Dynamics","en","master thesis","","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:1849ba18-6345-4562-a029-db9a4a0fc57f","http://resolver.tudelft.nl/uuid:1849ba18-6345-4562-a029-db9a4a0fc57f","Backward erosion piping: Experiments on erosion and progression rate","van Klaveren, Wouter (TU Delft Civil Engineering and Geosciences)","Jonkman, Sebastiaan N. (mentor); Pol, Joost (mentor); Mosselman, Erik (graduation committee); Delft University of Technology (degree granting institution)","2020","Backward erosion piping is a form of internal erosion where small pipes are formed below a dike. These pipes are formed in a direction opposite to the flow that transports sand particles. Piping is a very important failure mechanism in the protection of dikes, which can be unpredictable due to the different soil characteristics. Piping is well managed in the Netherlands, but there is a lot to be discovered regarding theerosion processes inside the pipe. For example, how fast the pipe develops and what this is dependent on. The objective of this thesis is to monitor and study the development of the pipe, to extend the knowledge about the different processes that influence the progression rate of the pipe. The main research question is: How do the different parameters and processes influence the progression and the sediment transport rate in laboratory experiments of backward erosion piping? To monitor the development of the pipe, different small-scale laboratory experiments were performed to obtain new data regarding piping and to study the influences of different parameters. The piping experiments were performed in three series: (1) configuration of the setup, (2) effect of grain size and (3) hydraulic loading. These experiments were performed in the previously developed setup of Vera van Beek (Van Beek, 2015). This setup was modified to measure the pore pressures and to guide the pipe through the middle of the setup. While conducting the experiments, different measurements were performed. This included measuring of the pipe length and geometry, collecting the sand boil and a dye injection to follow the flow. The literature study performed for this thesis has shown that in the past many experiments were performed regarding piping, but these studies did not focus on the different processes and the sediment transport rate of the pipe. By focussing on the progression phase of the pipe (continuous transport), the experimental data is compared to existing models (primary and secondary erosion). Sellmeijer’s model (Förster et al., 2012) is the current rule that is applied in the Netherlands for dike safety, but this model does not include time-dependency. This research showed that the development of the pipe is not a stationary process but depends on various conditions, such as
soil characteristics. The hypothesis formed at the beginning of this thesis listed several soil parameters which influence the progression rate of the pipe. Concerning the sediment transport rate of the pipe, Cheng’s model for bedload transport (Cheng, 2004) is evaluated and compared with the measured results. The analysis showed that the adapted formula of Cheng (Equation 2.24) overestimates the sediment transport rate in the pipe. From the analysis of the experimental results, it can be concluded that two parameters play an important role in the progression and sediment transport rate of the pipe: the particle diameter and hydraulic permeability. These parameters showed an influence on the progression rate which can be used to study piping on a larger scale. The most interesting result is the fact that experiments with a larger particle diameter have an overall larger progression rate.","Backward erosion piping; Progression rate; Sediment transport; Small-scale experiments; Experimental research","en","master thesis","","","","","","","","","","","","Civil Engineering | Hydraulic Engineering","",""
"uuid:ebb2f7b2-22c7-4358-a773-2a7d6b32c1d1","http://resolver.tudelft.nl/uuid:ebb2f7b2-22c7-4358-a773-2a7d6b32c1d1","Pilot Sand Groynes Delfland Coast: Efficiency and practical feasibility of a pulse nourishment","Hoekstra, R.","Stive, M.J.F. (mentor); Aarninkhof, S.G. (mentor); De Boer, G.J. (mentor); Van Koningsveld, M. (mentor); Luijendijk, A.P. (mentor); De Schipper, M.A. (mentor); Walstra, D.J.R. (mentor)","2010","In September and October of the year 2009, three sandgroyne nourishments have been executed at the Delfland Coast near the village of Ter Heijde. The nourishments have been executed to restore the sediment buffer in the upper part of the coastal profile. A sandgroyne is a concentrated amount of sediment (200.000m3) artificially nourished from the beach into the sea, appearing in the formation of peninsulas. It was anticipated that the three sandgroynes would be absorbed into the coastal system by the impact of waves and currents, nourishing the upper shoreface from the shoreline until a depth of about -5m NAP over a coastal stretch of about 2.5km. The construction and evolution of the sandgroynes have been monitored intensively. The following research objectives were proposed: 1) Assess the morphological evolution and practical aspects of the sandgroynes constructed at the Ter Heijde coast and 2) Use the site specific knowledge from the Ter Heijde pilot project to create a future perspective of sandgroyne nourishments as a common applied method to nourish the shoreface. This master thesis describes the process of the monitoring campaign, the results of a morhpological data analysis, the results of an initial model simulation set-up and a practical analysis. The sandgroynes have been absorbed in the coastal system, dominantly between the shoreline and the -5m depth contour. However the spatial scale of longshore sediment redistribution was larger than accounted for, driven by the intense wave climate. It is concluded that the sandgroynes can be an effective method for nourishing the shoreface, under flexible contract requirements that acknowledge the dynamics of the natural system.","Sandgroyne; Delfland Coast; Sediment transport; Nourishment; Sand engine; Bathymetry survey; Ter Heijde","en","master thesis","","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:fa4d3279-3443-41bc-a995-6d81f34d6936","http://resolver.tudelft.nl/uuid:fa4d3279-3443-41bc-a995-6d81f34d6936","Unravelling sediment transport driven by a multimodal wind-wave spectrum","Hoogervorst, Chris (TU Delft Civil Engineering & Geosciences)","Antolínez, José A. Á. (mentor); Aarninkhof, S.G.J. (mentor); Tissier, M.F.S. (mentor); Portilla‐Yandún, J. (graduation committee); Delft University of Technology (degree granting institution)","2022","This thesis analyses the importance and application of considering multiple coexisting wave trains in sediment transport predictions.
The wave trains at offshore and nearshore locations are analyzed by wave spectral partitions (Portilla at el., 2009). The temporal variability of consistently occurring wave trains can be analyzed through so-called wave families (Portilla et al., 2015). The wave partitions show that a unimodal wave spectrum occurs 35% of the time in front of the coast of the province of North Holland in the Netherlands. This means an error is introduced 65% of the time as unimodal spectra are assumed in traditional methods that use generalized wave parameters to estimate sediment transport. When the wave field is not unimodal, the angle between wave trains is considerable. Only 39% of the time is the angle between a wave train and the most energetic wave train smaller than 60°. For 43% of the time, the angle is between 60° and 120°. The remaining 17% are wave trains propagating in opposite directions. The difference in wave angle is half of the time larger than 50° when a threshold of one meter of deepwater significant wave height over the whole spectrum, defined by Holthuijsen (2007), is used.
Unsupervised machine learning techniques Principal Component Analysis, Maximum Dissimilarity Analysis, and the kmean clustering algorithm are used to group similar wave spectrums over time, spatially group wave families, analyze the wave climate's spatial-temporal variability, relate wave - and weather conditions, and assess their impact on wave-driven potential sediment transport. The Principal Component Analysis is used as a dimensionality reduction technique. This study shows the physical meaning of the Principal Components and their temporal variability in the wave frequency-directional spectrums, where Principal Components describe wave energy in each frequency-directional bin. The kmean clustering algorithm groups similar wave spectrums over time and gives insight into wave conditions, like calm and stormy conditions, called Sea States. The Maximum Dissimilarity Technique changes the focus between common conditions or extreme events. The wave partitions, wave families, and Principal Components give additional insight into the Sea States.
Potential sediment transport estimations are made by traditional methods that use a representative wave frequency and direction and through vectorizing and superpositioning the estimations by wave partitions and wave families. The outcomes show that it is challenging to predict sediment transport for multimodal wave conditions with state-of-the-art sediment transport formulations and models. The results show that the wave period significantly impacts sediment transport. The sediment transport for coexisting wave trains causes about 58% of the time more sediment transport than traditional methods. Here the not considered interaction between wave trains on bedload and sediment suspension will enhance sediment transport. Furthermore, the sediment transport estimations give insight into the wavefield and weather conditions that contribute most to the yearly wind-wave induced potential sediment transport caused by high energetic or consistently occurring conditions.
Between 2011 and 2020, 27.5 million m3 of sand has been nourished at the Ameland Inlet. Therefore, it might be considered as an erosion hotspot. Because of the fixed nourishment method of the Zandwindmolen and the continuous sand shortage at the Ameland Inlet, there is a match. However, the usefulness of a Zandwindmolen depends on the extent to which the nourished sand volume is dispersed by natural processes in the short and long term.
In this study, both the short- and long-term effect of a continuous point nourishment in a tidal channel is investigated for four sediment fractions (100, 200, 300 and 400 μm). The goal is that the sediment is dispersed by nature in order to allow the entire Ameland Inlet (adjacent coastlines, coastal foundation, outer delta and Wadden Sea basin) to grow along with sea level rise.
For optimal dispersion, the nourishment must be carried out by means of a spreader pontoon with a sediment mixture concentration of 1-2%. By doing so, a mixing plume is created in which sediment settles according to their individual settling velocity. This makes the mixing plume prone to the tidal ebb and flood current and can therefore be steered towards either the North- or Wadden Sea.
In the short term (time scale: instantaneous to a few weeks), it appears that the dispersion of sediment is mainly determined by the initial sedimentation process of sediment and by re-suspension of settling sediment particles. The dispersion by natural sediment processes is minimal. In the longer term (timescale: half a year) the sediment spreads further after it has settled to the seabed. Based on half a year, the total dispersion is mainly determined by the short term dispersion.
It is found that a continuous nourishment with the Zandwindmolen is expected to ensure that the intertidal areas in the eastern Wadden Sea can continue to grow naturally with (accelerated) sea level rise. Moreover, the natural distribution of the nourished sand will, through sediment connectivity, compensate for the erosion (autonomous and due to sea level rise) of the inlet (especially the outer delta) and is also expected to contribute to keeping the North Sea coast of Terschelling and Ameland safe. Therefore, the Zandwindmolen could be a useful new sustainable nourishment method in a tidal inlet.
Based on data from the White Volta River, a 1D Flume model is created using
HEC-RAS which tests several sediment transport functions and bed roughness parameters with constant bed slope, suspended and bed-load gradation in order to estimate sediment settling. The results suggest that during peak discharge events settled sediments are flushed up and over the weir. As peak discharges decrease, settling occurs based on particle diameter causing increased sediment storage up-stream until the next flushing event. The volume of sediment stored ramp is highly variable with respect to bed roughness and the used transport function, suggesting river calibration is required for concrete estimates. Based on the model results, approximately 1 − 2% of the White Volta’s yearly suspended load settles in-front of the structure before the discharge flushing event.","sand winning; white volta; Sediment transport; HEC-RAS; Weirs","en","master thesis","","","","","","","","","","","","Civil Engineering","",""
"uuid:7110dbd5-ab1a-44f7-aa7b-bcda86cdfeb2","http://resolver.tudelft.nl/uuid:7110dbd5-ab1a-44f7-aa7b-bcda86cdfeb2","Feasibility of Beneficial Reuse of Sediment for Mangrove Rehabilitation in Paramaribo, Suriname","Pröpper, Jeroen (TU Delft Civil Engineering & Geosciences)","van Prooijen, Bram (mentor); Kranenburg, W.M. (mentor); Winterwerp, J.C. (mentor); Vijverberg, Thomas (mentor); Smits, Bob (mentor); Delft University of Technology (degree granting institution)","2023","In response to the escalating coastal erosion at the Weg naar Zee region in Suriname, this study explores the beneficial reuse of dredged sediment from the Suriname River. The integral question is, ”What is the feasibility of the beneficial reuse of dredged sediment through sediment nourishment to rehabilitate the growth of mangrove forest on the Weg naar Zee, Suriname coast?” To address this, literature research provides a basis for understanding imperative areas related to mud coast dynamics, sediment dynamics, mangroves, and the Suriname coastal system. This culminates in a system analysis and develops into a conceptual model of the Suriname River Estuary’s dynamics. Further development of a hydrodynamic numerical Delft 3D model of the Suriname River Estuary system ensues. This analysis forms the foundation for further assessment of potential sediment input locations throughout the estuary. Simulations are utilized to verify the sediment transport mechanisms, primarily focusing on two transport types: initial transport through the water column as suspended particulate matter (SPM), and migration over the bed influenced by wave forcing. These simulations offer valuable data on the impact of timing and placement of sediment input on the transport and deposition process. Employing recent survey data of the Weg naar Zee shoreline’s foreshore, a schematisation was established to ascertain the total infill volume necessary for a convex-up profile favourable for mangrove rehabilitation conditions. The results demonstrate the feasibility of achieving this profile by strategically inputting sediment, hence, capitalising on both transport types in the estuary. The study concludes by reiterating that the strategic placement of sediment nourishments can be a viable means of restoring the Weg naar Zee coastline. Finally, possible subsequent studies to address the existing uncertainties and streamline the implementation strategy are discussed.","Delft3D; Mangrove rehabilitation; Suriname; Sediment transport; Building with Nature","en","master thesis","","","","","","","","","","","","Civil Engineering | Hydraulic Engineering","","5.901703843881134, -55.219280872813144"
"uuid:8cb4a201-f48b-4bf9-a692-600c18dbc900","http://resolver.tudelft.nl/uuid:8cb4a201-f48b-4bf9-a692-600c18dbc900","Sediment transport during the execution of the pilot nourishment Ameland Inlet: Development of a tool for analysing bathymetric surveys, applied on the pilot nourishment Ameland inlet","van Rhijn, Thijs (TU Delft Civil Engineering & Geosciences)","Wang, Zhengbing (mentor); van Prooijen, Bram (mentor); Vos, S.E. (mentor); de Looff, Harry (mentor); Tonnon, Pieter Koen (mentor); van Dijk, Erik (mentor); Delft University of Technology (degree granting institution)","2019","Within the KustGenese 2.0 research project a 5Mm3 pilot nourishment is created on the ebb-tidal delta of Ameland. For this thesis I was involved in the parties; Van den Herik, the contractor who executed the work, Deltares and Rijkswaterstaat. A tool is created to quickly analyse new surveys in combination with the ships deposit data. The tool is applicable for any other dredging project.
The tool is applied on the 4-6 weekly surveys during the execution of the pilot nourishment. An analyse with the tool gives insight into the morphodynamics of the ebb tidal delta and the location of the pilot nourishment. The sediment transport on the nourishment location is wave dominated, as the sediment transport is limited during calm wave conditions. The sediment transport on the second ebb shield is however tide dominated. During the January 2019 storms an increase in sediment transport is seen on both tidal and wave dominated parts.","Ameland Inlet; Ameland; ebb-tidal delta; Van den Herik; Rijkswaterstaat; Deltares; Kustgenese; Sediment pathways; Nourishment; Sediment transport","en","master thesis","","","","","","","","","","","","Civil Engineering","Pilot Nourishment","53.483564, 5.548447"
"uuid:4b24f4ed-f533-45b5-9d43-3dbf820a0a80","http://resolver.tudelft.nl/uuid:4b24f4ed-f533-45b5-9d43-3dbf820a0a80","The application of a continuous nourishment on wave and tide-dominated systems","Rutteman, Hoyte (TU Delft Civil Engineering & Geosciences; TU Delft Hydraulic Engineering)","Aarninkhof, S.G.J. (mentor); Antolínez, José A. Á. (mentor); Luijendijk, Arjen (mentor); van Maren, D.S. (mentor); Kollen, Jan (mentor); Delft University of Technology (degree granting institution)","2021","The Sandwindmill system could decarbonize the Dutch coastal protection whilst harmonizing with the building with nature approach. The system consists of a pipeline connecting an offshore borrow location to a nearshore area, where the mined sediment is discharged. The equipment is powered by wind turbines. As long as the wind blows sufficiently, sediment is pumped through the system, leading to a near-continuous nourishment. After the sediment has left the pipes, natural forces should distribute the material. Despite the considerable environmental benefit, one substantial challenge is the financial competitiveness with the traditional hoppers. This research aims to provide insights that can enable the system to be also financially competitive to the hoppers. In the first part, an integral analysis of the Sandwindmill is carried out. The second part of this thesis focuses on the optimization of the dispersion of the nourished sediment.
In the first part, all sub-systems of the Sandwindmill concept are treated separately. Wind data, theoretical formulations, and an exploration of the mining options are used to identify optimization opportunities. From the assessment, it becomes apparent that the interdependency of these sub-systems complicates the cost-optimization. Hence, a competitive system design requires an accurate harmonization of these sub-systems. Three main conclusions are drawn. First of all, the costs per cubic meter decrease with an increasing nourishment volume. Finding the marginal costs is essential in determining the feasibility of the system for certain volumes. Secondly, it is concluded that - given an annual nourishment volume - the pump capacity and windmill size should be attuned. Their cost-optimum is found at a set-up that leads to a yearly operational time of approximately 70%. Lastly, the analysis shows that the application of batteries to support the system in case of lower wind velocities can contribute to a more economical system. This is mainly the case if the system has wave-induced limited operational times.
Due to the costs of the displacement of the pipe outlet and the financial benefits of nourishing large volumes, the second part of the research aims at generating guidelines to designing a dispersive nourishment. Both wave- and tide-dominated systems are a potential field of application for the Sandwindmill. North-Holland is selected as an appropriate case study, containing the Marsdiep tidal inlet and a wave-dominated closed coastal section. A process-based coastal area model is set up to determine the sensitivity of different nourishment strategies on the dispersion at a one-year timescale. A tidal channel wall nourishment at the Marsdiep and a shoreface nourishment at Callantsoog are assessed.
One of the key findings of the second part is that the strong tidal velocities at the Marsdiep inlet are more capable of transporting the nourishment than the conditions at the wave-dominated coast. After one year, the distance travelled by a significant part of the nourished sediment is a factor four higher for the Marsdiep nourishment. Secondly, the research shows that the grain size plays a vital role in the local and regional dispersion. Therefore, the borrowed grain size should be part of the system design. Under the evaluated scenarios, the nourishment application under forcing conditions with a higher transporting potential has a smaller effect in the longer term. This implies that the optimal operational time could be determined solely based on the cost-optimization and should hence be around 70%.