Toward a More Flood Resilient Urban Environment: The Dutch Multi-level Safety Approach to Flood Risk Management

The new EU Floods Directive requires flood risk reduction for areas where risk is deemed significant; for these zones, flood risk management plans must be prepared. In line with these requirements, the Netherlands has opted for a 'multi-level safety' approach, which includes prevention, protection and preparedness responses. This paper describes the application of the multi-level safety approach to the case of the Island of Dordrecht in the Netherlands. For this case study, the flood risks were mapped based on flood depth and arrival time. The results of the risk mapping show that nearly the entire island is at high-risk. A further area perspective map recommends focusing on national- and regional-scale measures for the Island of Dordrecht. Following these results, this paper examines the effectiveness of two alternative regional-scale responses to flood risk reduction: On the one hand, the complete reinforcement of the primary dike ring, and on the other, a partial reinforcement together with a compartmentalisation dike. It is shown that both options can significantly reduce the expected annual damages and number of casualties. The cost-efficiency of each has also been investigated. In this regard, it is concluded that the combination of a partial reinforcement and a compartmentalisation dike is economically feasible.