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The traditional approach to dike reinforcement (a bigger dike) is usually the first option that comes to mind when a dike is no longer fit for purpose, even though there may be more attractive alternatives from several points of view.

A sandy foreshore consists of a large quantity of sand that is deposited in front of a dike. This body of sand attenuates the waves and therefore eliminates or reduces the impact of the waves on the dike, avoiding the need to strengthen the dike.

In many locations, a sandy foreshore will be cheaper to install and maintain than a traditional dike upgrade. Moreover, the approach is more sustainable and it improves nature and leisure facilities in the area. This pilot project created a test site to study the behaviour of a sandy foreshore. The project is part of the Dutch Flood Protection Programme.

Hybrid Flood Defence Houtribdijk

Goal

A sandy foreshore to strengthen a dike is already a proven solution on seashores. However, in other locations – lakes, for example – more evidence is needed and we need to learn more about the effectiveness of this type of solution in specific circumstances. This project will provide answers to questions about the impact of waves on the foreshore and the effect of the growth of vegetation on the stability of the foreshore. This knowledge can be used to formulate criteria for the selection of suitable locations for foreshores.

Hybrid Flood Defence Houtribdijk 4

Infographic of the pilot. for a high resolution version download the factsheet below under Downloads

Approach

This is a large-scale pilot study located on the Houtrib Dike between the cities of Enkhuizen and Lelystad in the Netherlands. A 450-metre-long foreshore test section was constructed in the summer of 2014. It consisted of a body of sand of approximately 70,000 m³ that varied in width and height. Different types of vegetation were planted on the foreshore in the spring of 2015 to test the effectiveness of a range of situations simultaneously.

Research

The foreshore test section will be monitored for four years. Monitoring includes water levels as well as wave strength measurements. Two cameras have been installed to make a picture of the site every hour (a time-lapse animation with these pictures can be seen below). A topographic survey will be conducted several times per year. All the data collected will be analysed to answer the research questions. In 2016, a preliminary answer will be given to the question of how a secure, stable and cost-efficient sandy foreshore can be designed for use in lake systems (see publications below). The final results of the project will be published in 2018.

Coastline rotation at pilot section

This film shows a timelapse of the coastline rotation made by the on-site camera.

Contact

Hybrid Flood Defence Houtribdijk 5
Henk Steetzel
Project Manager

Partners

The partnership for the project Hybrid Flood Defence Houtribdijk consists of Rijkswaterstaat and Ecoshape. Within Ecoshape the following organizations participate: research institutions Deltares and WUR Environmental Research, contractors Boskalis and Van Oord and engineering companies Arcadis, RoyalHaskoningDHV and HKV – Lijn in Water. Deltares and Alterra are responsible for the research and development programme. The project is supervised by Henk Steetzel (Arcadis).

  • Houtrib Dike Pilot Project

    Arcadis

  • Sand nourishment Galgeplaat

    Rijkswaterstaat

  • Community 10

    HKV

  • Community 5

    Boskalis

  • Marker Wadden 10

    Wageningen Marine Research

  • Community 6

    Deltares

  • Community 19

    Royal Haskoning DHV