Timu Gallien (Scripps Institution of Oceanography)
Urban Coastal Flood Prediction
Globally, coastal flooding represents a significant humanitarian and socioeconomic hazard for urbanized communities. Flood mapping is the first step in risk assessment and represents a critical element of risk management, however flood maps are not rigorously validated to include information about model sensitivities and uncertainties relative to modeling methodology and infrastructure resolution. A two dimensional Godunov type hydrodynamic model that solves a local Riemann problem to accommodate weir-like overflow is successfully applied to simulate tidal flooding. The shallow water hydrodynamic model is then augmented with temporally variable empirical overtopping estimates to investigate the effect of wave overtopping volumes. Simulation results are compared to two unique validation datasets and three critical issues in coastal flood prediction emerge; the effects of methodology (i.e. equilibrium vs. hydrodynamic), depiction of both weir-like overflow of walls and wave runup and overtopping volumes and finally, resolving flood control infrastructure and mitigation measures. Hydrodynamic modeling methodologies responsive to flood control infrastructure outperform traditional equilibrium flood mapping. Weir-like and wave runup and overtopping volumes are shown to significantly influence flood predictions, and results show that accurate flood mapping requires flood defense walls are resolved with centimetric accuracy and that flood mitigation measures (e.g., storm system management, berming) are depicted.