Many flood defenses (dikes, dams and dunes) around the globe are in need of upgrades to protect the hinterland against flooding during extreme storm events. Sandy retrofits, where a sandy beach system is placed in front of an exisiting flood defense, are a novel engineering approach using sediment instead of stones and asphalt to guarantee coastal safety. Much of our understanding of sand deposits, or nourishments, stem from research in coastal areas that are dominated by energetic waves. However, the redistribution of sand and the evolution of different sediment sizes of potential retrofits is not understood in environments which are under the influence of both strong tidal currents and waves (i.e. mixed-energy systems).

The EURECCA project aims to develop robust and quantitative knowledge of mixed-sand transport, inclsuidng shells, driven by mixed-energy forcing. This project will focus on the recently completed Prins Hendrikzanddijk, a sandy retrofit of a dike on the back-barrier side of the Dutch barrier island of Texel, an area with strong tidal currents and relatively weak wind-driven waves: a typical mixed-energy system.

The project includes:

• Continuous monitoring and a 6-week field campaign (SEDMEX; mixed SEDiments in Mixed Energy eXperiment) at the Prins Hendrikzanddijk to measure the forcing conditions that mobilize sand of different grain sizes.
• Laboratory experiments (TraSSh; Transport of Sand with Shells) to study how shells and shell fragments affect sediment transport.
• Numerical modelling with Delft3D and XBeach to further generalize our findings.

Two PhD researchers, Jorn Bosma (Physical Geography, Utrecht University) and Marlies van der Lugt (Hydraulic Engineering, TU Delft) work in tandem on the project. The research team works together closely with a diverse group of dedicated end-users: Jan de Nul B.V., Waterproof B.V., Hoogheemraadschap Holllands Noorderkwartier, Deltares, Arcadis, and the Dutch Ministry of Public Works Rijkswaterstaat.

• prof. dr. Maarten Kleinhans
• prof. dr. Gerben Ruessink

• Marlies van der Lugt
• Matthieu de Schipper

Monitoring and assessment of coastal dynamics relies on high-frequency observations, which are time-consuming or costly. This project uses a "Citizen Science" approach to engage the public in our ongoing coastal research. 

Coastal areas are recreational hotspots where people actively engage with their environment. To occasional visitors, the coast may appear relatively static, but regular beachgoers are often aware of the ever-changing sea, beach and dunes. Engaging the public in the collection of such observations provides a cost-effective method to acquire observational data. At the same time, this Citizen Science approach provides an opportunity to raise awareness of coastal dynamics. Accordingly, with this project we aim to (1) collect crowd-sourced observations and (2) communicate our coastal research outcomes in an understandable way to a wide audience.

We build upon the methodology used within the international CoastSnap (Harley & Kinsela, 2022) network, where users (“citizens”) contribute by submitting smartphone photos of shoreline positions through the CoastSnap app, e-mail or social media, at fixed photo points. We extended this approach by directing users to a custom-built webapp after scanning a QR-code. This way, users can directly capture ("snap") and submit their uncompressed photo file, after which theyare instantly rewarded with the result of their processed image. To provide this instant feedback on shoreline positions, we automated the georectification and shoreline detection using machine learning and object detection. The existing MATLAB routines were converted and extended to Python, to make the CoastSnap approach even more accessible and interoperable for other citizen science initiatives. 

We currently host four CoastSnap locations using this approach (at Egmond aan Zee, Petten (2x), Noordvoort and the Prins Hendrikzanddijk on Texel), and aim to include other sites and coastal features of interest. Besides the instant feedback after submitting a photo we currently communicate updates through Twitter, Facebook and a dedicated website.

• Math van Soest

A common measure to prevent erosion of beach-dune systems and warrant coastal safety is to add large amounts of sand on the beach or in the shallow water directly fronting the beach. These nourishments are intended to be redistributed across the beach-dune system by natural processes. Embryonic dunes are a clear expression of this onshore sand transport and may provide suitable indicators for the effectiveness of nourishments, both in terms of safety and ecological impact. In this project, we aim to study how nourishment strategies affect the physical and ecological drivers of embryonic dune development along sandy coasts.

• prof. dr. Merel Soons
• prof. dr. Gerben Ruessink

• drs. Petra Damsa (Rijkswaterstaat)
• drs. Quirijn Lodder (Rijkswaterstaat)

In this project I aim to unravel how alongshore variability in the submerged part of the beach leads to alongshore variations in beach and dune characteristics. I hypothesize that so-called Shoreward Propagating Accretionary Waves (SPAWs) play an important role in the cross-shore exchange of sand within the sandy beach system.
SPAWs are concentrated accumulations of sand that emerge from subtidal sandbars and migrate to the beach. As such, they act as natural nourishments, leading to alongshore variability in morphology.
Using a combination video images from different field sites, newly collected field data, and numerical modelling I aim to unravel SPAW behaviour and their role in the development of alongshore-variable beach and dune characteristics.

• dr. Kathelijne Wijnberg (Univ. Twente)
• drs. Quirijn Lodder (Rijkswaterstaat)
• dr. Bruno Castelle (Univ. Bordeaux I)
• dr. Bas Arens (Arens bureau for beach and dune research)
• Shore Monitoring & Research