Author(s): Maarten Schoemaker; Wilfred De Kam; Constantijn Steenbergen; Richard Blokpoel; Geert-Jan Van Der Sanden

Linked Author(s):

Keywords: Intertidal area; Estuarine; Nature; Nature based solutions; Flood risk; Flood probability; Safety standards; Probabilistic; Recreation; Hydraulic structures; Culvert; Control gates; Storm surge barrier

Abstract: Waterdunen is a unique intertidal estuarine nature area of 350 ha. It is located along the North Sea, but inland of the primary water defense. By means of a tidal culvert through the primary flood defense, a safe intertidal area is be created inland in which estuarine nature with salt marshes could develop with a total wet area of around 214 ha. This estuarine nature attracts many types of birds, including little egrets, spoonbills, shelducks, black-headed gulls and sandwich terns among others. As the tidal culvert controls the water levels, the intertidal area is safe from flooding, even during strong storms. This allowed other types of developments to take place as well, such as the construction of walkways, holiday homes, a testing ground for salty crops and an oyster farm. Many visitors are attracted to the Waterdunen tidal area, giving the local economy a significant boost. The development of Waterdunen had its challenges. In 2017 new safety standards for flood defenses were introduced in the Netherlands. The new safety standards require a full probabilistic approach to estimate the flood probability behind the primary water defenses. Hence, there was a need for a full probabilistic framework to prove that the failure probability of the tidal culvert through the primary water defense meets these new safety standards. With this framework, it could be proven that the original design was exceeding the new safety standards. This meant that adjustments had to be made. These include an electromechanical installation with increased reliability (where automatic closure by gravity is crucial), an improved control system and a consequence analysis whether failure would lead to flooding. With these adjustments, the probability of failure of the tidal culvert could be significantly reduced to a level within the required safety standards, even with 50cm of sea level rise. This paper will elaborate on how failure can be defined, and which steps are taken in this framework to estimate the resulting failure probability. It will also elaborate on some of the aspects of the final electromechanical installation and control system that allow for the tidal culvert to be a success. This framework can be used in the design and assessment of other similar structures where a safe intertidal area behind the primary water defense is considered, also on a bigger scale.

DOI: https://doi.org/10.64697/978-90-835589-7-4_41WC-P1619-cd

Year: 2025