Performance-based management of flood defence systems

Abstract

The results of mathematical modelling of three flooding scenarios due to levee breaking in the middle Po river (northern Italy) are presented. In this area some catastrophic floods that occurred in the nineteenth century caused the formation of several levee breaks and the inundation of wide plains (500–600 km2), with considerable water depths (6–7 m). The inundation dynamics as a result of a levee break occurring at different locations along the right river bank of the Po river were modelled using as upstream boundary condition a synthetic design hydrograph of 200 years return period. The hypothetical breaches were located where the historical ones occurred more frequently or where the more severe consequences of the flooding were expected. Three scenarios were numerically simulated with a two-dimensional mathematical model based on the shallow water equations solved by means of the well-known MacCormack finite difference scheme. When possible, a calibration of the model parameters on the basis of the available information about recent and historical events was performed. The fairly good agreement between computed results and historical data suggests that the proposed approach is capable of reproducing the main characteristics of the phenomenon, giving support to the design of flooding maps for risk assessment.