The impact of the uncertainty of dike breach development time on flood hazard

The impact of uncertainty of dike breach development time on breach probabilities of downstream dikes and flood hazard was investigated by means of a Monte-Carlo-based probabilistic-deterministic flood hazard model. Three scenarios of breach development time were compared – one fixed-time scenario and two scenarios with stochastically generated breach development time. For the latter two scenarios, the dependency between the ultimate breach width and breach development time was modelled using a fully-dependent and a fully-independent copula. The simulation results suggest that in view of uncertainty in the flood hydrograph shape, dike breach locations, breach points in time and ultimate breach widths, the uncertainty due to the dike breach development time and dependence structure with the ultimate breach width should not be neglected when simulating multiple interdependent breaches. A significant difference in dike failure probabilities was simulated for a number of dikes in a 100-year flood scenario. Large changes in flood hazard are, however, relatively unlikely for a selected river reach.