Five years of Prins Hendrik zanddijk
Type:
Presented during:
CEDA Dredging Days 2024
Authors:
J. Fordeyn, G. Vanwesenbeeck, and K. Foré
Abstract
In October 2019, the construction of the Prins Hendrik Zanddijk (PHZD) on the Dutch island Texel was completed. It is one of the showcase projects of the Dutch flood defense scheme (Hoogwaterbeschermingsprogramma). While the remainder of the existing Waddensea dike on Texel was reinforced with new clay and asphalt layers, an artificial dune and beach landscape was built at the seaward side of the dike protecting the Prins Hendrik Polder. This strategy allowed to combine flood defense with nature development, public services and recreational appeal. The design was innovative, building on the knowledge of only a handful dune-for-dike nature-inspired designs along the Dutch North Sea coast, such as Hondsbossche-Pettemer Zeewering and Kustwerk Katwijk. Contrary to these examples, the Prins Hendrik Zanddijk is located at a sheltered coast where currents prevailed to wind-driven forces impacting the sandbody. Another difference is that there is no natural dune or beach near the project location that could function as a sand source. Consequently, morphological response and longterm stability of the design were uncertain. The design-and build contract for the construction of the PHZD, that was awarded to Jan De Nul, included a five-year maintenance period, in which the different functions of the Zanddijk were safeguarded by means of Key Point Indicators and their intervention values. During these five years, an extensive monitoring program was realized, covering different aspects, such as settlement, hydrodynamic and aeolian sand transport, pumping station outflow, groundwater quality and bird habitats. The observations led to several interventions concerning vegetation, recreation and sand drift that improved the performance and experience of the area. The uncertainties associated with the project have triggered several research lines that will contribute to mainstreaming dune-in-dike nature-inclusive designs.
Keywords: Coastal Protection, Maintenance, Monitoring, Research, Nature-based Solutions