Sand Engine

The effects of the feedback between the changing coastal morphology and the wavefield on the generation and propagation of large scale (O(1-10 km)) shoreline sand waves is examined with a quasi-2D morphodynamic model. Traditional shoreline change models do not include this feedback and are only able to describe diffusion of shoreline sand waves and furthermore they are unable to describe migration. It is found with the present model that if there is a dominant littoral drift, the feedback causes downdrift migration of coastline features no matter if they grow or decay. Consistently with previous studies, simulations show that a rectilinear coastline becomes unstable and sand waves tend to grow spontaneously from random perturbations, if the wave incidence angle is larger then about 42o (θc) at the depth of closure (high angle wave instability). The initial wavelengths at which the sand waves develop are 2-3 km and this is similar to previous linear stability analysis. The implicatio...

Using line modeling, in the scope of the NOURTEC project a prediction is made concerning the behavior of the shoreface nourishment of Terschelling and an evaluation concerning the behavior of the combined supply on beach and shoreface at Norderney. Computations suggest smaller longshore diffusitivity on the upper beach than on the zone between NAP-1 m to-3 m for Terschelling and the inverse for Norderney (groynes 1). Cross-shore diffusitivity at Norderney appears to be much larger than at Terschelling. If further investigations substantiate those results, these lead to the conclusion, that shoreface nourishment at Norderney is still more preferable than at Terschelling.

Morphodynamic models can play a key role in assessing the likely impact of coastal developments. A major goal is the prediction of predicting coastal evolution over a regional scale. The deterministic approach to morphological prediction was pioneered by Pelnard-Considere (1956) who presented a one-line equation to forecast changes in coastline position. Subsequent models have extended this to multiple depth contours. Such models, however, do not forecast accurately the variability likely to be experienced in real situations. One alternative to the deterministic modelling approach is to employ stochastic forecasting methods, such as Monte Carlo methods. A key input to this type of model is the statistical description of the wave climate or other driving forces. However, to obtain physically meaningful results very many realisation are needed. In this paper we formulate and solve moment equations for the shoreline position. These equations describe the averaged or long-term solution, and its dependence on wave-climate; and eliminates the need for computationally intensive Monte-Carlo simulations.

As many coastal areas of the world suffer from chronic erosion, innovative solutions beyond traditional local nourishment must be explored. One such solution is the implementation of mega-nourishments (MNs), where a large sediment volume is deposited in a single location and redistributed via natural processes, thereby feeding adjacent beaches. Robust numerical modeling methods are needed to evaluate potential MN sites at coastal locations around the world. Two oneline numerical modeling approaches of MN evolution are presented using the Coastline Evolution Model (CEM) and GENESIS þ Cascade (GenCade). Both models are parameterized for the Sand Motor (SM) that has been constructed on the Dutch coast to explore the feasibility of the MN approach. Here, a variety of K coefficients in the Coastal Engineering Research Center (CERC) sediment transport equation are tested since traditionally calibrated and used values may not apply for MN features. Both models are found capable of reproducing the shoreline morphological patterns observed at the SM over the first 3.5 years. GenCade shows a low difference between measured and modeled coastline position overall, showing accurate predictions of absolute shoreline position. CEM is able to capture feature tip migration due to its wave shadowing algorithm. The best results from both models can be obtained for higher K values than those commonly suggested in the literature. Given the size of a mega-nourishment relative to traditional nourishments, it is likely that a higher-than-usual K value may be a better fit when simulating mega-nourishments in a one-line model.

In order to improve the effectiveness of artificial nourishments a replenishment outside of the beach itself was taken into consideration for a prototype test. Contradictory to the earlier six conventional beach nourishments the material was deposited both on the shoreface and on the beach. The fate of the combined shoreface and beach nourishment was as well as that of the preceding conventional beach replenishment intensively monitored including field investigations of bathymetry, hydro-and sediment dynamics. On the basis of these data and additional application of mathematical models the effectiveness of this new type of nourishment has been evaluated in comparison with a conventional beach replenishment.

In the last decade, innovative beach nourishment strategies have been developed, driven by the increased worldwide interest in environmentally friendly coastal protection measures. In this context, the massive nourishment project of the Netherlands, known as Sand Engine, begun in 2011, has been hailed as a successful means of beach protection. Continuous monitoring, field campaigns, and numerical modeling have shown that the great volume of sand deployed is gradually transported by the waves and currents along the coastline, avoiding the need for repeated invasive, small scale beach replenishments. A very small, bell-shaped Sand Engine was designed to protect the beachfront at a tourist resort near Puerto Morelos, Mexico. To estimate the morphological response of the beach and the functioning of the micro Sand Engine as a sand reservoir, XBeach numerical modelling was applied to the project. The micro Sand Engine is seen to be a sustainable and eco-friendly coastal protection measure, especially applicable when a large nourishment project is not viable. Maintenance work for the nourishment is cost and time effective, and any negative impacts to sensitive ecosystems nearby can be detected and controlled quickly.

The uses of beach fill in the countries of the European Union are highlighted and discussed with respect to the general situation, project type and objectives, design and evaluation procedures, legal framework, and financial aspects. As expected, significant differences were found among the investigated countries. In general, the study shows that it would be very profitable for south European countries to learn about the Dutch and German practices, particularly regarding the long-term coastal management and the regular monitoring of the coastal morphology. On the other hand, recent Dutch experience has shown that their legal system is a bit rigid, leading sometimes to renourishments that are less necessary to reach the global objective.

In Aveiro (NW coast of Portugal), a coastal monitoring programme was carried out in sequence of a shoreface nourishment intervention (over than 2 M m3) performed in 2020. In this programme, almost one year of biweekly subaerial topographies and quarterly bathymetric surveys have been collected along a 10 km coastal stretch between June 2020 and June 2021. In this study, topographic and bathymetric surveys were analysed to assess the expectation that if the shoreface nourishment is located in sufficiently shallow water depths, its landward movement will feed adjacent beaches and, consequently, increase the subaerial beach volume. Results show that the subaerial beach volume is well correlated with the 1.05 m (above MSL) isoline displacement through time. While the seaward limit of the shoreface nourishment moved landwards about 200 m, the shoreline proxy (isoline of 1.05 m) displayed a maximum seaward displacement of 60 m. The displacement of the shoreline proxy was highly variable i...

In flood protection, the dominant paradigm of 'building hard structures' is being challenged by approaches that integrate ecosystem dynamics and are 'naturebased'. Knowledge development and policy ambitions on greening flood protection (GFP) are rapidly growing, but a deficit remains in actual full-scale implementation. Knowledge is a key barrier for implementation. To analyse conditions for the implementation of GFP, a knowledge-arrangement perspective is developed. The knowledge-arrangement perspective is applied on a case study of successful implementation of GFP in the Netherlands, the pilot Sand Engine Delfland, a large-scale (21.5 Mm 3) sand nourishment project. This project confirms that an integrated knowledge arrangement enables GFP as it allows for multifunctionality. Effectiveness of the integrated arrangement in this project is explained by its 'flexible' nature providing ample design space. This was possible because core values in flood protection and nature were not part of the integrated arrangement. More generally the case study demonstrates the difficulties of implementing GFP in existing mainstream flood protection routines. These are not (yet) geared to incorporate uncertainty, dynamics and multifunctionality, characteristics associated with GFP. The Sand Engine project can be regarded as a 'field laboratory' of physical and institutional learning and an innovation for mainstream flood protection.

In the Netherlands it is common to nourish the coastline with sand from the seabed. Foredunes are replenished with sand from the beach and can be transported further into the dune area. We investigated whether nourishment material alters the phosphorus (P) content of dune soil and the nitrogen (N):P ratio of dune vegetation in two areas: a mega sand nourishment with fixed foredunes (SE) and a traditional sand nourishment with dynamic foredunes (NWC). Four zones were considered: beach (zone 1), frontal foredunes (zone 2), foredunes crest (zone 3) and inner dunes (zone 4). We estimated the characteristics of fine (b 250-μm) and coarse (250-2000 μm) sand. Total P, P speciation and available P of SE and NWC were similar until zone 4. Zone 1-3 consisted mainly of coarse sand, whereas the sand in zone 4 was finer with higher amounts at NWC. Iron (Fe) bound P was comparable for fine and coarse sand in zone 1-3, but high contents were present in zone 4. In zone 1-3, calcium (Ca) bound P was mainly found in the fine fraction, which was abundant in the coarse fraction of zone 4. After a period of 4 years, the effect of dynamic dunes on P fractions and dune plant species was not apparent yet, although inblowing sand mainly consisted of fine sand with high contents of Ca-bound P. This may change over time, especially in dynamic dunes with higher eolian activity of fine sand. Consequently, pH buffering of the soil may increase because of a higher Ca-carbonate content, which leads to decreased solubility of Ca-bound P and low P

A morphodynamic model based on the wave-driven alongshore sediment transport, including crossshore transport in a simplified way and neglecting tides, is presented and applied to the Zandmotor meganourishment on the Dutch Delfland coast. The model is calibrated with the bathymetric data surveyed from January 2012 to March 2013 using measured offshore wave forcing. The calibrated model reproduces accurately the surveyed evolution of the shoreline and depth contours until March 2015. According to the long-term modeling using different wave climate scenarios based on historical data, for the next 30-yr period, the Zandmotor will display diffusive behavior, asymmetric feeding to the adjacent beaches, and slow migration to the NE. Specifically, the Zandmotor amplitude will have decayed from 960 m to about 350 m with a scatter of only about 40 m associated to climate variability. The modeled coastline diffusivity during the 3-yr period is 0.0021 m 2 /s, close to the observed value of 0.0022 m 2 /s. In contrast, the coefficient of the classical one-line diffusion equation is 0.0052 m 2 /s. Thus, the lifetime prediction, here defined as the time needed to reduce the initial amplitude by a factor 5, would be 90 yr instead of the classical diffusivity prediction of 35 yr. The resulting asymmetric feeding to adjacent beaches produces 100 m seaward shift at the NE section and 80 m seaward shift at the SW section. Looking at the variability associated to the different wave climates, the migration rate and the slight shape asymmetry correlate with the wave power asymmetry (W vs N waves) while the coastline diffusivity correlates with the proportion of high-angle waves, suggesting that the Dutch coast is near the high-angle wave instability threshold.

In the Netherlands it is common to nourish the coastline with sand from the seabed. Foredunes are replenished with sand from the beach and can be transported further into the dune area. We investigated whether nourishment material alters the phosphorus (P) content of dune soil and the nitrogen (N):P ratio of dune vegetation in two areas: a mega sand nourishment with fixed foredunes (SE) and a traditional sand nourishment with dynamic foredunes (NWC). Four zones were considered: beach (zone 1), frontal foredunes (zone 2), foredunes crest (zone 3) and inner dunes (zone 4). We estimated the characteristics of fine (b 250-μm) and coarse (250-2000 μm) sand. Total P, P speciation and available P of SE and NWC were similar until zone 4. Zone 1-3 consisted mainly of coarse sand, whereas the sand in zone 4 was finer with higher amounts at NWC. Iron (Fe) bound P was comparable for fine and coarse sand in zone 1-3, but high contents were present in zone 4. In zone 1-3, calcium (Ca) bound P was mainly found in the fine fraction, which was abundant in the coarse fraction of zone 4. After a period of 4 years, the effect of dynamic dunes on P fractions and dune plant species was not apparent yet, although inblowing sand mainly consisted of fine sand with high contents of Ca-bound P. This may change over time, especially in dynamic dunes with higher eolian activity of fine sand. Consequently, pH buffering of the soil may increase because of a higher Ca-carbonate content, which leads to decreased solubility of Ca-bound P and low P

Since 1990, the Dutch coastline is maintained within the ‘Dynamic Preservation’ program, according to which the coastline is maintained seawards from a reference line, mainly by applying nourishments. Research into the maintenance of the Dutch coast is continuous and causes the content of the coastline preservation program to change constantly since the initiation in 1990. In recent years, the switch was made from yearly nourishment programs to the use of multiannual nourishment programs, in which an interim nourishment planning is included for 4 years. Next to the nourishments following the ‘Dynamic Preservation’ program, ten large reinforcements were applied along the Dutch coast in the past decade according to the ‘Zwakke Schakel’ project. After reinforcement, the coastline at the ‘Zwakke Schakel’ locations needs continuous maintenance to remain at the desired position. The combination of the long term maintenance at the ‘Zwakke Schakel’ locations and the multiannual nourishment ...

Satellite imagery provides a unique source of data given its spatial and temporal coverage. In this study, a detection algorithm has been developed and tested to automatically determine the satellite derived waterline (SDW). The SDWs have been compared with traditional coastline measurements at two locations along the Dutch coast, where high quality in-situ data is ample available. The findings are that the SDW can be detected with sub pixel precision, with offsets of about 6.5 m in case of Sentinel-2 images. Also for longer time scales, similarities are found between coastline dynamics based on the SDW positions and traditional indicators based on topographic measurements, hence the SDW may serve as a coastal state indicator. This shows that a time series of SDW positions can be used to study coastal dynamics for any coastal stretch to get a first understanding of the coastline evolution in the period of 1984 –

Since the end of 2000, a continuous sampling to monitor PCDDs and PCDFs emission was implemented on the 11 municipal waste incineration ovens in Walloon Region, to check the compliance with the EU emission limit value, 0.1 TEQ ng/Nm³. For this purpose, uncertainty estimation is one of the most crucial points for decision making. The sampling and analytical uncertainty was estimated by two different ways: 1. Identification and quantification of the major contributions through QA/QC data (type A evaluation) or by other sources (type B evaluation), 2. Direct assessment through specific duplicate measurements. Both ways were found to give results in good agreement, with an extended uncertainty of about 30 to 40%, depending on the congener, with a coverage factor k=2.

As many coastal areas of the world suffer from chronic erosion, innovative solutions beyond traditional local nourishment must be explored. One such solution is the implementation of mega-nourishments (MNs), where a large sediment volume is deposited in a single location and redistributed via natural processes, thereby feeding adjacent beaches. Robust numerical modeling methods are needed to evaluate potential MN sites at coastal locations around the world. Two oneline numerical modeling approaches of MN evolution are presented using the Coastline Evolution Model (CEM) and GENESIS þ Cascade (GenCade). Both models are parameterized for the Sand Motor (SM) that has been constructed on the Dutch coast to explore the feasibility of the MN approach. Here, a variety of K coefficients in the Coastal Engineering Research Center (CERC) sediment transport equation are tested since traditionally calibrated and used values may not apply for MN features. Both models are found capable of reproducing the shoreline morphological patterns observed at the SM over the first 3.5 years. GenCade shows a low difference between measured and modeled coastline position overall, showing accurate predictions of absolute shoreline position. CEM is able to capture feature tip migration due to its wave shadowing algorithm. The best results from both models can be obtained for higher K values than those commonly suggested in the literature. Given the size of a mega-nourishment relative to traditional nourishments, it is likely that a higher-than-usual K value may be a better fit when simulating mega-nourishments in a one-line model.

In Aveiro (NW coast of Portugal), a coastal monitoring programme was carried out in sequence of a shoreface nourishment intervention (over than 2 M m3) performed in 2020. In this programme, almost one year of biweekly subaerial topographies and quarterly bathymetric surveys have been collected along a 10 km coastal stretch between June 2020 and June 2021. In this study, topographic and bathymetric surveys were analysed to assess the expectation that if the shoreface nourishment is located in sufficiently shallow water depths, its landward movement will feed adjacent beaches and, consequently, increase the subaerial beach volume. Results show that the subaerial beach volume is well correlated with the 1.05 m (above MSL) isoline displacement through time. While the seaward limit of the shoreface nourishment moved landwards about 200 m, the shoreline proxy (isoline of 1.05 m) displayed a maximum seaward displacement of 60 m. The displacement of the shoreline proxy was highly variable i...

The Upper Texas Gulf Coast is notorious for high erosion rates. In order to adequately mitigate erosion in this area, innovative solutions beyond the traditional local nourishments and flood protection schemes must be explored. As a method of reducing recurring linear nourishment costs and frequent beach disruption from nourishment activities, a mega-nourishment on the Dutch coast, the Delftland Sand Engine, has been constructed to test the feasibility of using large-scale nourishments to feed sediment material to adjacent beaches. While the benefits and drawbacks of this specific mega-nourishment pilot project are still being evaluated, the potential advantages could make this approach a viable alternative for the Texas coast where erosion rates and nourishment costs are high.

In Aveiro (NW coast of Portugal), a coastal monitoring programme was carried out in sequence of a shoreface nourishment intervention (over than 2 M m3) performed in 2020. In this programme, almost one year of biweekly subaerial topographies and quarterly bathymetric surveys have been collected along a 10 km coastal stretch between June 2020 and June 2021. In this study, topographic and bathymetric surveys were analysed to assess the expectation that if the shoreface nourishment is located in sufficiently shallow water depths, its landward movement will feed adjacent beaches and, consequently, increase the subaerial beach volume. Results show that the subaerial beach volume is well correlated with the 1.05 m (above MSL) isoline displacement through time. While the seaward limit of the shoreface nourishment moved landwards about 200 m, the shoreline proxy (isoline of 1.05 m) displayed a maximum seaward displacement of 60 m. The displacement of the shoreline proxy was highly variable i...

Sand nourishments are a widely applied technique to increase beach width for recreation or coastal safety. As the size of these nourishments increases, new questions arise on the adaptation of the coastal system after such large unnatural shapes have been implemented. This paper presents the initial morphological evolution after implementation of a mega-nourishment project at the Dutch coast intended to feed the surrounding beaches. In total 21.5 million m 3 dredged material was used for two shoreface nourishments and a large sandy peninsula. The Sand Engine peninsula, a highly concentrated nourishment of 17 million m 3 of sand in the shape of a sandy hook and protruding 1 km from shore, was measured intensively on a monthly scale in the first 18 months after completion. We examine the rapid bathymetric evolution with concurrent offshore wave forcing to investigate the feeding behaviour of the nourishment to the adjacent coast. Our observations show a large shoreline retreat of O (150 m) along the outer perimeter of the peninsula, with locally up to 300 m retreat. The majority (72%) of the volumetric losses in sediment on the peninsula (1.8 million m 3 ) were compensated by accretion on adjacent coastal sections and dunes, confirming the feeding property of the mega nourishment. Further analyses show that the morphological changes were most pronounced in the first 6 months while the planform curvature reduced and the surf zone slope flattened to pre-nourishment values. In the following 12 months the changes were more moderate. Overall, the feeding property was strongly correlated to incident wave forcing, such that months with high incoming waves resulted in more alongshore spreading. Months with small wave heights resulted in minimal change in sediment distribution alongshore and mostly cross-shore movement of sediment.

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.