Cost-benefit analysis to select the optimal flood protection strategy along the Scheldt

Abstract

The Scheldt estuary is a unique tidal estuary. The river originates from France and flows through Belgium and the Netherlands. The tide creates important flood risks in the Flanders region, including for the city of Antwerp. The Flemish government wants to update its flood protection policy, based on a cost-efficient reduction of risks of flooding and taking into account sea level rise. Against this background, the Flemish Waterway Administration commissioned a cost-benefit analysis of flood protection measures. To this purpose a series of models of different scientific disciplines was integrated within a cost-benefit analysis framework. Results of cost-calculation, hydraulic, ecological and agricultural models were integrated in a cost-benefit model. Protection against flooding was evaluated on a risk based approach. This means that not only probabilities of flooding were considered but also possible damages sustained by flooding. Consequently a non-homogeneous level of security was allowed. Measures evaluated include storm surge barriers nearby Antwerp or on tributaries, dike heightening and creating controlled inundation areas (floodplains). Constructing reduced tide areas which allows creation of new wetlands was also assessed. Benefits of nature development were taken into account when comparing costs and benefits of these measures. An optimal flood protection strategy was developed, and the optimal solution was tested using different kinds of uncertainty analyses for a wide variety of technical and economic parameters. The analysis showed that cost-benefit analysis is a very useful approach to assist decision-making processes on designing flood protection measures and this approach is certainly applicable to other estuaries.