Author(s): Maarten Schoemaker; Matthijs Bos; Michael Van De Watering; Joost Buurman; Matthijs Kok; Sebastiaan N. Jonkman
Linked Author(s): Matthijs Bos
Keywords: Flood protection flood risk adaptation pathways hydraulic infrastructure climate change robustness robust decision making increments discount rates
Abstract: Singapore is currently working on their masterplan for large-scale and long-term coastal protection. PUB, Singapore’s National Water Agency, works with a projection of 2.0m relative sea level rise (rSLR) by the year 2150. In planning and design of protection measures from coastal flooding, the question arises what steps are cost-optimal (least Present Value of the investments) to protect to the eventual 2.0m rSLR. Should the infrastructure be constructed in one step to 2.0m rSLR? Or should infrastructure be constructed in several smaller increments? For six archetypes of coastal protection that may be applied in Singapore, these step sizes have been optimized by estimating cost-optimal pathways. These archetypes are: a coastal revetment, a setback embankment, a quay wall, a singular flood wall, a closure dam and a storm surge barrier. The archetypes can be split up into two different categories: structures that are mostly expandable (usually sloped and soil solutions such as coastal revetments and setback embankments) and structures that would mostly need to be replaced (usually concrete or steel structures such as storm surge barriers and quay walls). They differ in that expandable structures have limited fixed costs per increment (mobilization costs) and high variable costs (the costs of additional protection), while replaceable structures have high fixed costs (the base of the structure) and limited variable costs for additional protection. However, expandable structures (such as an embankment) can be fitted with replaceable elements (such as a sheet pile or concrete pattern placed revetment) and replaceable structures can be made expandable as well, by designing a foundation that can withstand higher than initial design loads and longer than initial lifetimes, allowing room for expandability when the initial design loads are exceeded. Each archetype has been worked out by means of a case study along the Singaporean coast and possible preliminary designs for different increment sizes until 2.0m rSLR. Each possible pathway to 2m rSLR has been assessed to determine which pathway is cost-optimal. With the future being inherently uncertain, a sensitivity analysis has been performed with different climate change and economic scenarios to assess the robustness of the pathways. This extended abstract will elaborate on some of the recommendations that can be made for all six archetypes within a Singaporean context.
Year: 2025