Building with nature applied for the Western Scheldt: modelling storm surge attenuation by a double dike system

Abstract

The world’s largest deltas are starved in sediment while the sea level keeps rising. Hundreds of millions of people become more vulnerable to flooding’s by the end of this century. The urge to rethink the current coastal protection system is larger than it has ever been. Ecological based coastal engineering has the potential to provide an answer to the problem as can offer long-term sustainability and resilience, a double dike system is an application of building with nature. The goal of this research is to understand if a double dike system could attenuate a storm surge wave in an estuary. The Western Scheldt estuary is used as a test case. A conceptual model in Python is developed, dividing the estuary in three sections, water flow is calculated with the equations of Chezy. Selecting the friction as calibration parameter, the model is calibrated based on measurements from Rammegors and Perkpolder. The model is validated using another period from the two polders, selecting the appropriate calibration parameter based statistical tests. Results show that adding polders increases the attenuation capacity, adding larger polder results in a higher attenuation capacity. All the polders have an optimal inlet area at which the attenuation capacity is maximal. A large scale implemented double dike system can reduce the maximal water level in the Western Scheldt during a storm surge by 11%. This research has provided a first insight in the potential of the attenuation capacity of double dike system which can be applied in estuaries worldwide.