Adaptation Tipping Points and Pathways | Towards a long-term perspective on the solution space of coastal adaptation in the Southwestern Delta in the Netherlands

Abstract

In the coming century and beyond it is certain that sea-level will continue to rise, having a big impact on millions of people and their environment. However, the extent and rate of future sea-level rise (SLR) remain uncertain. To address the consequences posed by future SLR, long-term adaptation planning is needed (IPCC, 2022). This thesis aims to explore the solution space for coastal adaptation to SLR in the Southwestern Delta of the Netherlands. Central question of the thesis is: “which adaptation tipping points (ATP’s) and adaptation decisions are most decisive for the solution space for coastal adaptation to SLR, focussing on the Southwestern Delta and the management targets here for the sandy coastlines, flood risks and freshwater supply ”? It presents an assessment that considers the risk caused by an ATP, as well as the need for incremental or transformational measures to reduce this risk, referred to as the “decisiveness” of an ATP. Insight into pivotal decisions could provide short-term action and potentially avoid mal adaptation. Dutch water management favours adaptive delta management via a DAPP approach (Haasnoot et al., 2019c). Within four solution directions (“Protect-closed”, “Protect-open”, “Seaward” and “Accommodate”) the solution space of adaption to SLR can be described. This thesis is based on the same approach. ATP’s were collected for the Southwestern Delta based on available reports and data bases and analysed. For the (sub)-basins of the Southwestern Delta, a few ATP’s were aggregated with exception of the Eastern Scheldt basin, where substantial ATP’s were aggregated. Consequently, the focus of this thesis is predominantly on the Eastern Scheldt basin as the main aim is to develop and test a method to determine the decisiveness of ATP’s. Further research is required to decide if all used ATP’s represent the complete picture in the Southwestern Delta. Findings of ATP assessment of the Eastern Scheldt basin are amongst others that, with higher sea-levels more decisive ATP’s occur and incremental adaptations may result in transformational adaptations. For example, with a minimal SLR of 1 meter the decision to keep the Eastern Scheldt basin open or closed arises. In this thesis all (sub)-areas were assessed separately. It is recommended to conduct a follow-up study in which the sub-areas of the Southwestern Delta are combined based on the method assessed in this thesis