Decision alternatives for the safety of the Eastern Scheldt

Abstract

After the disastrous floods in 1953 in the Netherlands, measures are taken to improve the safety in the Netherlands. In the Southwest of the Netherlands a couple of tidal basins are closed by the construction of dams and storm surge barriers. The closure of tidal basins shortens the coastal length and can result in a cost reduction comparing with heightening of dikes. The Eastern Scheldt storm surge barrier is one of the most well-known storm surge barriers. In view of the expected sea level rise the Deltacommission 2008 stated that the barrier cannot operate safely at a sea level rise of more than 1,0m and preferably, therefore, has to be removed. Furthermore the barrier causes sand hunger whereby large parts of the sandbars will ultimately disappear under water. This will affect subterranean animals and birds which are dependent on the sandbars. When the barrier will be removed these consequences can (largely) be prevented. In this study the best decision alternative for the safety of the Eastern Scheldt is investigated in view of costs and flood risk. This is done by defining two alternatives: (1) maintaining the Eastern Scheldt storm surge barrier and (2) removing the Eastern Scheldt storm surge barrier. In the analysis 3 scenarios of sea level rise are regarded: the current sea level, a sea level rise of 0,5m and a sea level rise of 1,0m. The consequences of the alternatives, such as the required dike reinforcement (heightening and widening) and reinforcements on the barrier, are determined and a cost-benefit analysis is made. It turns out that, if the current safety standard is satisfied, maintaining the barrier is a lot cheaper than removing the barrier. This is partly due to the magnitude of the costs for the removal of the barrier. When the safety is based on the values to be protected around the Eastern Scheldt, it turns out that the optimum flooding probability is 1/500 per year. The required dike height can be lower in that case, but still maintaining the barrier is cheaper.