A Rational Method for the Design of Sand Dike/Dune Systems at Sheltered Sites; Wadden Sea Coast of Texel, The Netherlands

A rational method for the design of sand dike/dune systems at sheltered sites is presented, focussing on the cross-shore dimensions of the sand dike in relation to the local wave climate, tidal regime and available sandy materials. The example case is the new sand dike/dune system along the south-east coast of Texel, The Netherlands. The old dike protecting the island was not sufficiently strong to withstand an extreme storm event and has been strengthened by a new sand dune/dike. Various empirical and numerical models have been used, compared and validated to determine the erosion volumes during annual conditions and extreme storm events. Potential wind-induced (aeolian) sediment transport and erosion is also studied using the modified Bagnold-equation including the effects of grain size, moisture content and vegetation. The overall design method resulted into an innovative design solution, guarantying a naturally integrated and resilient sand protection as well as optimal coastal safety.