  The dynamics of flooding are primarily influenced by the shape, height, and
roughness (friction) of the underlying topography. For this reason, mechanisms
to mitigate floods frequently employ structural measures that either modify
topographic elevation, e.g., through the placement of levees and sandbags, or
increase roughness, e.g., through revegetation projects. However, the
configuration of these measures is typically decided in an ad hoc manner,
limiting their overall effectiveness. The advent of high-performance surface
water modeling software and improvements in black-box optimization suggest that
a more principled design methodology may be possible. This paper proposes a new
computational approach to the problem of designing structural mitigation
strategies under physical and budgetary constraints. It presents the
development of a problem discretization amenable to simulation-based,
derivative-free optimization. However, meta-heuristics alone are found to be
insufficient for obtaining quality solutions in a reasonable amount of time. As
a result, this paper proposes novel numerical and physics-based procedures to
improve convergence to a high-quality mitigation. The efficiency of the
approach is demonstrated on hypothetical dam break scenarios of varying
complexity under various mitigation budget constraints. In particular,
experimental results show that, on average, the final proposed algorithm
results in a 65% improvement in solution quality compared to a direct
implementation.
