Analysis of the Effects of Reservoir Operating Scenarios on Downstream Flood Damage Risk Using an Integrated Monte Carlo Modelling Approach

The aim of this study is to analyse the effects of reservoir operating scenarios, for flood damage evaluation downstream of a dam, using a Monte Carlo bivariate modelling chain. The proposed methodology involves a stochastic procedure to calculate flood hydrographs and the evaluation of the consequent flood inundation area by applying a 2D hydraulic model. These results are used to estimate the inundation risk and, as consequence, the relative damage evaluation under different water level conditions in an upstream reservoir. The modelling chain can be summarized as follows: single synthetic stochastic rainfall event generation by using a Monte Carlo procedure through a bivariate copulas analysis; synthetic bivariate stochastic inflow hydrograph derivation by using a conceptual fully distributed model starting from synthetic hyetographs above the derived; flood hydrographs routing through the reservoir taking in an account of the initial level in the reservoir; flood inundation mapping by applying a 2D hydraulic simulation and damage evaluation through the use of appropriate depth-damage curves. This allowed for the evaluation of the influence of initial water level on flood risk scenarios. The procedure was applied to the case study of the floodplain downstream from the Castello reservoir, within the Magazzolo river catchment, located in the southwestern part of Sicily (Italy).