Adaptation measures and pathways for flood risk in Dordrecht

Abstract

In line with the Adaptive Delta Management approach of the Dutch Delta Programme, Dordrecht has developed a multi-layer safety strategy to meet the future tasking for flood risk management. This strategy puts greater emphasis on limiting the consequences of floods through spatial planning (layer 2) and emergency management (layer 3), in addition to protection from floods through dikes (layer 1). The reasoning process and measures related to the new strategy are as follows. The proposal of the Delta Programme sub-programme Safety for updating the protection standards has made it possible to invest in strengthening specific dike segments, where it is most cost-efficient. By transforming the northeastern dike segment into an extra strong dike, Dordrecht can be safer than with an economically optimal standard for the entire dike ring -- for about the same cost. This targeted measure in layer 1 is sufficient to meet the basic safety level (chance of fatalities is not higher than 1/100,000) and reduces the risk of social disruption (large groups of casualties) to virtually none. Economic damages and casualties due to a dike breach in the Northwest or in the South can be reduced by using regional defences as compartmentalisation (layer 2). In addition, compartmentalisation of the dike ring area enables the creation of a "safe haven" for preventive evacuation on the island itself (layer 3). This also calls for thorough preparation for floods, e.g. by robust design of critical infrastructure networks and improved risk and crisis communication. The multi-layer safety strategy for Dordrecht ensures that the objectives for flood risk management are met in a timely and efficient manner, that opportunities for mainstreaming adaptation and for spatioeconomic development are taken advantage of, and that unnecessary costs of potentially irreversible measures are avoided.