Author(s): Enrique Soriano; Andrea Petroselli; Davide Luciano De Luca; Ciro Apollonio; Salvatore Grimaldi; Luis Mediero

Linked Author(s): ciro apollonio, Luis Mediero

Keywords: Climate Change; Floods; Hydrological Dam Safety; Rainfall-Runoff models; Stochastic rainfall generator

Abstract: Dam breaks can cause important economic and human losses. Therefore, several regulations and recommendations for their construction and maintenance aim to guaranty their safety. The failure of such infrastructure can be driven by floods that exceed the design spillway capacity. Usually, design floods are estimated through a statistical analysis of observed data in the past, though such data are usually short. Moreover, design floods are usually estimated for high return periods greater than 500 years, and climate change is expected to increase the frequency and magnitude of floods in the future. Therefore, new methodologies to assess hydrological dam safety considering short observed data and climate change are required. In this study, a stochastic methodology to assess hydrological dam safety considering climate change is presented. The methodology is applied to the Eugui dam on the Arga river in the north of Spain. The Eugui dam has a gated spillway. The stochastic model STORAGE (De Luca and Petroselli, 2021) based on the Neymann-Scott Rectangular Pulse Model has been used to simulate long time series of precipitation. The model generates a maximum of 500 years of rainfall at high resolution. Delta changes extracted from precipitation projections of 12 climate models, three periods (2011-2040, 2041-2070, 2071-2100) and two emission scenarios (RCP 4.5 and RCP 8.5) (Garijo and Mediero, 2019) are used to consider climate change in the STORAGE model. The precipitation time series generated stochastically are transformed into runoff time series by using the COSMO4SUB model (Grimaldi et al., 2021). It is a continuous model that uses as input data a high-resolution digital terrain model, land cover / soil type data, and the precipitation supplied by the STORAGE model, providing as output a continuous runoff time series from which it is possible to extract annual maximum hydrographs. Time series of annual maximum hydrographs are considered as inflow hydrographs to the reservoir. The Volume Evaluation Method (MEV) (Girón, 1988) is applied to simulate the operation of spillway gates, obtaining maximum water levels in the reservoir and outflow hydrographs. The MEV method specifies when the gates should be opened and closed to reach the target final water level, based on the reservoir curve and spillway capacity. Hydrological dam safety is assessed with the frequency curve of maximum water levels in the reservoir for the 12 climate models, three return periods and two emission scenarios mentioned above. Therefore, the methodology proposed allows practitioners and dam owners to check the hydrological dam safety requirements detailed in the regulations, accounting for climate change.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022877

Year: 2022