A new methodology for flood hazard assessment considering dike breaches

Abstract

[1] This study focuses on development and application of a new modeling approach for a comprehensive flood hazard assessment along protected river reaches considering dike failures. The proposed Inundation Hazard Assessment Model (IHAM) represents a hybrid probabilistic-deterministic model. It comprises three models that are coupled in a dynamic way: (1) 1D unsteady hydrodynamic model for river channel and floodplain between dikes; (2) probabilistic dike breach model which determines possible dike breach locations, breach widths and breach outflow discharges; and (3) 2D raster-based inundation model for the dike-protected floodplain areas. Due to the unsteady nature of the 1D and 2D models and runtime coupling, the interdependence between the hydraulic loads on dikes at various locations along the reach is explicitly considered. This ensures a more realistic representation of the fluvial system dynamics under extreme conditions compared to the steady approaches. The probabilistic dike breach model describes dike failures due to three failure mechanisms: overtopping, piping and slope instability caused by seepage flow through the dike core (micro-instability). The 2D storage cell model computes various flood intensity indicators such as water depth, flow velocity, and inundation duration. IHAM is embedded in a Monte Carlo simulation in order to account for the natural variability of the input hydrograph form and the randomness of dike failures. Besides binary (wet/dry) inundation patterns, IHAM generates new probabilistic flood hazard maps for each intensity indicator and the associated uncertainty bounds. Furthermore, the novel probabilistic dike hazard maps indicate the failure probability of dikes for each considered breach mechanism.Citation: Vorogushyn, S., B. Merz, K.-E. Lindenschmidt, and H. Apel (2010), A new methodology for flood hazard assessment considering dike breaches, Water Resour. Res., 46, W08541,

Dike-break induced flows: a simplified model

“…First, 2D numerical simulations show that q is constant along the critical section, which is consistent with Eq. (14). Since F = 1 everywhere on the critical section, a constant q implies a constant h along the same section.…”

“…The use of a simplified model instead of a classical SWE-based model to compute this distribution greatly reduces the computational time. The derivation of such a simplified model is made easier by two legitimate assumptions: at the timescale of a whole flood event, the first transient phase during which the breach widens is short [1,14] and the discharge through the breach tends to a steady value [11,12].…”

Simplified graphical tools for assessing flood-risk change over large flood-prone areas

“…Vorogushyn et al, 2010) are then used to assess the expected amount of economic damages in the study area. The scientific literature reports a wide set of depth-damage curves, in which the percentage of damage of a specific asset is related to the water depth.…”

Prospects and requirements for an operational modelling unit in flood crisis situations

“…The conventional way of premodelling the consequences of events in form of hazard maps can only assess a limited number of scenarios, 2016) though. Thus, the high uncertainties render it impossible to ensure that a specific situation is reflected by prepared hazard maps in an acceptable way in case of the occurrence of an event [4,5].…”