A Holistic Approach to Coastal Protection for the Prins Hendrik Polder
Type:
Presented during:
WODCON XXII - Enhance the Harmony between Dredging and Ecology
Authors:
J. Fordeyn, E. Lemey and L. Perk
Abstract
"The Prins Hendrikzanddijk project on the Dutch island Texel is an integral project where flood defense is combined with nature development, public services and recreational appeal. Seaward of the existing dike, a dune is landscaped to act as primary coastal protection. The existing dike thereby loses its main function, but remains in place as a scenic element. Instead of using a classical engineering design approach with rule and compass, the inclusion and enhancement of public, recreational and ecosystem services are made the focal point of the design. A unique and dynamic nature reserve with dunes, salt marsh and beach in front of the current dike was designed, with the goal of upgrading some 200 hectares of the Wadden Sea area (UNESCO World Heritage Site). Central to the design are the interactions between ecology and sediment dynamics. In traditional hydraulic engineering, there is a trade-off between safety and ecological value, and between sediment stability and dynamics. Coarse sand resists erosion better, but provides a less suitable habitat for benthos, which makes the area less attractive to wading birds. Therefore, the target species and habitats were analyzed and sediment characteristics chosen accordingly. A specific strategy of including fine sands to stimulate benthos growth is applied. Other strategies for habitat creation include salt marsh recuperation and seashell patches. The design further deals with a trade-off between recreational opportunities and the natural habitat disturbance, and between the dynamics of soft coastal protection and the lifetime of public functions. Project specific KPI’s are assigned and monitored during construction and a five-year maintenance period. This paper presents a nature-based solution for enhancing a coastal defense system while maximizing the ecological value of the area. A soft design is laid out, where safety, nature, recreation, agriculture and public services come together."
Keywords: Dredging, Ecological dredging. Ecosystem Services. Nature-based solution.