Location: Houtribdijk, Markermeer (NL)
Date: 2014-2018 (pilot and monitoring)
Involved parties: EcoShape (Deltares, WUR Environmental Research, Boskalis, Van Oord, Arcadis, Royal Haskoning DHV, HKV and Alterra), Ministry of Infrastructure and the Environment (Rijkswaterstaat)
Technology Readiness Level: 7 – system prototype demonstration in operational environment
Keywords: Sandy shore, Natural flood defense, dike re-enforcement, coastal lake morphodynamics, vegetated foreshores
A sandy foreshore consists of a large quantity of sand, which is placed before the existing dike. This body of sand reduces the strength of the waves, thereby eliminating or reducing the impact of the waves on the dike.
A sandy foreshore is in many places cheaper to construct and maintain than a traditional dike reinforcement. Moreover, it is more durable and enhances the natural and recreational facilities and possibilities of an area.
Traditionally when a dike needs strengthening the dike will be heightened (dike reinforcement). The dike does then not provide any additional ecological or recreational benefits.
A comprehensive monitoring program captured the development of the sandy foreshore and the vegetation growth (RWS/EcoShape-stuurgroep pilot Houtribdijk, 2015). The objective of the Houtrib Dike Pilot Project was to stimulate the implementation of sandy solutions in front of dikes under mild wave conditions, to be able to achieve a cheaper realization of flood defense system and possibly maintenance free flood defense system. This was done by focusing on three themes:
- To find an optimized design
- To be able to incorporate a sandy solution in the safety check of the dike
- To get insight in the maintenance phase and the accompanying costs
The knowledge gained from the Pilot Houtrib Dike is applied substantially in the development of the greater sandy foreshore defense of the Marker Lake, adjacent to the pilot project site.