Vegetated foreshores for flood risk reduction

A pilot study in lake Marken, the Netherlands

Flood defense structures can be strengthened via traditional coastal engineering, such as dike heightening or the application stronger revetments. Recently, natural foreshores have received a lot of attention because of their wave attenuating capacity. In this study, a full-scale pilot study was carried out, in which a vegetated foreshore was constructed along a dike in the large shallow lake Marken in the Netherlands.

HKV was part of an Ecoshape consortium, responsible for the design, construction and monitoring of the foreshore. Waves, currents, bathymetry, sediment characteristics and vegetation were measured continuously, forming the basis of an extensive research program. The monitoring showed that such a foreshore can reach a stable profile shape in a time span of just a couple of years. That implies that foreshores can be applied for effective wave energy dissipation in lake environments. The pilot has provided both local and generic knowledge on the value of hybrid dike-foreshore solutions for flood risk reduction and additional ecosystem services. The knowledge base provided by the pilot was used for the reinforcement of the Houtribdijk, a large dam separating the lakes IJssel and Marken. This Houtribdijk was successfully reinforced with sand and vegetation, at both sides of the dam over a distance of 12 km.