Abstract
Climate change and deterioration require a continuous effort to reinforce flood defences and meet reliability requirements. To efficiently upgrade flood defence systems, insight in costs and benefits of measures at a system level is required throughout the process of planning and design. Due to the size of flood defence systems the number of possible decisions is large, which hampers system optimization. We describe a greedy search algorithm that can find (near-)optimal combinations of reinforcement measures for dike segments. The algorithm has been validated by comparing results for 2800 different dike segments to an integer programming implementation. The difference in objective value (Total Cost) is only 0.04% on average, which is small compared to other uncertainties in assessment and design of dike segments. The algorithm is applied to a reinforcement project for a dike segment of 41 independent sections, and compared to the common design practice which uses reliability-based requirements on a section level. It is found that the resulting reinforced dike segment is 42% cheaper to construct than the one obtained from the common approach, based on the same input information. This illustrates the practical and societal value of the design approach using a greedy search algorithm in this context.
Highlights
IntroductionIn many delta regions around the world, systems of flood defences (e.g., dikes, dunes and hydraulic structures) have been constructed to mitigate risks from flooding [1,2]
In many delta regions around the world, systems of flood defences have been constructed to mitigate risks from flooding [1,2]
In order to show that the heuristics yieldoptimal solutions, we evaluate the performance of the greedy algorithm and compare it with a Mixed Integer Programming (MIP) implementation in CPLEX 12.9 [40] using branch-and-cut, for a large number of different dike segments
Summary
In many delta regions around the world, systems of flood defences (e.g., dikes, dunes and hydraulic structures) have been constructed to mitigate risks from flooding [1,2]. The subsoil in delta regions is typically very heterogeneous, which means that the strength of dike segments is very non-homogeneous. This means that the system reliability is determined by that of different (partially) independent elements. Each section is susceptible to various failure modes, most notably inner slope instability, piping erosion and overtopping. This is not always to the same extent, and the cost for increasing reliability is not the same for each failure mode and can vary per section (for instance due to lack of space due to neighbouring residential areas)
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