Safe Dike Heights at Minimal Costs: The Nonhomogeneous Case

Dike height optimization is of major importance to the Netherlands as a large part of the country lies below sea level and high water levels in rivers can cause floods. A cost-benefit analysis is discussed in Eijgenraam et al. (2010), which is an improvement of the model Van Dantzig (1956) introduced after a devastating flood in the Netherlands in 1953. We consider the extension of this model to nonhomogeneous dike rings, which may also be applicable to other deltas in the world. A nonhomogeneous dike ring consists of different segments with different characteristics with respect to flooding and investment costs. The individual segments can be heightened independently at different moments in time and by different amounts, making the problem considerably more complex than the homogeneous case. We show how the problem can be modeled as a MINLP problem and present an iterative algorithm that can be used to solve the problem. Moreover, we consider a robust optimization approach to deal with uncertainty in the model parameters. The method has been implemented and integrated in software, which is used by the government to determine how the safety standards in the Dutch Water Act should be changed.