Adaptive design of flood defence systems

Abstract

Climate change is increasingly becoming more impactful on our society. Recent events such as the extreme rainfall in the summer of 2021 in Germany, Belgium and The Netherlands and hurricane Ida in Mississippi (USA), caused severe floodings and damages in these areas. Climate change, in turn, leads to an increase in sea level rise, making flood prone areas more at risk for floodings. However, the magnitude of rise in sea level is of an uncertain nature. This bolsters the idea of applying adaptive designing methods on flood defence systems to tackle the uncertainties decision makers and engineers face in the wake of climate change, whilst finding a balance between safety and expenditures. In this research, I apply adaptive design methods on the Rhine-Meuse estuary to develop an adaptive flood defence system in a system-to-structure approach. Thus, to converge onto a flood defence structure, three design loops are considered. In the first loop multiple adaptive systems are designed with the Dynamic Adaptive Policy Pathways, showing various flood defence options and other required measures to allow the functioning of the systems, as a function of sea level rise. To select an adaptive system in which an adaptive flood defence structure is developed, a set of preferred pathways (systems) are designed and quantified in three sea level rise scenarios. This leads to a preferred open/closable system in which a storm surge barrier is developed to replace the current Maeslant barrier at the end of its life span. In the second loop a Multi Criteria Analysis is applied to determine a preferable location and barrier type, which resulted in the adoption of a sector gate barrier near Maasdijk. In the third design loop, a reliability model is developed to determine whether designing barrier in an adaptive manner is (economically) beneficial to cope with uncertainties surrounding that of sea level rise and the relative structural failure probability of the barrier over a range of sea level rise scenarios. With the model I was able to produce data about the balance between structural safety of various designs and construction costs of the barrier. Subsequently, the model provided substantiated data about which components of the barrier provide a high level of confidence in returning positive economical benefits when designed as adaptive. The applied method in this thesis shows promise, however, to further develop adaptive designing methods it is important to apply the approach in other, quantitative, case studies.