Author(s): Francesco Macchione; Andrea Antonella Graziano; Domenico Ferraro

Linked Author(s): Francesco Macchione, Andrea Antonella Graziano, Domenico Ferraro

Keywords: Dam breach; Flood wave; Propagation; Dimensionless analysis

Abstract: When a dam break occurs, a flood wave is generated and propagated downstream. Since the released volume of water can reach hundreds of millions of cubic meters, this kind of event is characterized by a marked catastrophic character. For predictive purposes, i.e., the evaluation of dam break flood hazard, there is a need for reliable models for both the computation of the dam break hydrograph and the flood wave propagation. Dam break modelling has in itself different uncertainties, especially if the failure affects an earthen dam. In this case, the rupture, known in the literature as dam breach, is a progressive erosion of the embankment induced by the water flow over the breach due to the emptying of the reservoir. Therefore, dam breach modelling involves several complexities, such as the breach development over time, to manage which assumptions need to be made, introducing some model parameters. The number of parameters depends on the kind of dam breach model. If a simplified physically-based model is used, the main schematization concerns the shape of the breach, thus the uncertainties of the hydrograph computation are related to some shape parameters. The uncertainties on the calculation of the hydrograph also affect the propagation of the flood wave along the downstream reach. In this work, the propagation of the dam breach hydrographs will be studied and, in particular, the effect of varying dam breach model parameters on the flood wave routing will be examined. Different values of flood volume, longitudinal downstream slope and dam breach model parameters will be considered and the sensitivity of flood routing to these parameters will be studied, by carrying out simulations on prismatic channels. With the same dam-reservoir system, different model parameters lead to different dam breach hydrographs as well as peak discharges at the dam. Presenting the results in dimensionless form, this difference is shown to be progressively reduced while propagating downstream. These results allow to highlight the situations that require a careful choice of the dam breach model parameters, in order to obtain a safe evaluation of the downstream flooded areas.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221090

Year: 2022