Author(s): Enrique Soriano; Kai Schroter; Sophie Ullrich; Marco Lompi; David Santillan; Luis Cueto-Felgueroso; Luis Mediero

Linked Author(s): Kai Schröter, Marco Lompi, Luis Mediero

Keywords: Climate Change; Flood Losses; SaferPlaces; Urban Floods

Abstract: In recent decades, urban areas and population densities have increased considerably, leading to changes in flood exposure. In addition, climate change has modified the pattern of floods: date of occurrence and flood magnitude. Therefore, flood losses are likely to change in the future. A methodology is proposed to quantify the effect of climate change on flood losses in urban areas. Climate change projections, a distributed hydrological model, a two-dimensional hydrodynamic model, and a flood loss model are integrated to quantify the expected changes in fluvial flood losses in the Pamplona metropolitan area (Spain) driven by the River Arga with a catchment area of 500 km2. Twelve climate models, two emission scenarios (RCP 4.5 and RCP 8.5) and three periods (2011-2040, 2041-2070 and 2070-2100) were used to obtain delta changes in precipitation quantiles (Garijo and Mediero, 2019). Peak flow delta changes in the River Arga catchment were obtained by using precipitation quantile delta changes as input data in the Real-Time Interactive Basin Simulator (RIBS) distributed hydrological model (Lompi et al., 2021). The 2D hydrodynamic model (IBER) is used to assess fluvial flood hazards in the Pamplona metropolitan area. A high-resolution digital terrain model (DTM) with a cell size of 1 meter is used. The IBER model was calibrated with streamflow data recorded at four gauging stations of the SAIH system of the River Ebro Basin Authority and the flood extents in real flood events supplied by the Regional Government of Navarre. Flood hazards generated by synthetic flood hydrographs have been simulated for the seven return periods, three periods, and two emission scenarios mentioned above. Such synthetic hydrographs are obtained by applying the peak flow delta changes to the 15-min flood hydrographs extracted from recorded data at gauging stations. The result of these simulations consists of mean water depths and flood extents in the study area. The Safer_DAMAGE algorithm (Paprotny et al., 2020; Paprotny et al., 2021) developed within the SaferPlaces project estimates fluvial flood losses for residential and commercial buildings. Safer_DAMAGE uses OpenStreeMap building footprints, socio-economic statistical data, and mean water depths to estimate flood losses. The Safer_DAMAGE algorithm was validated in the Pamplona metropolitan with the database of flood loss compensations in the period 1996 -2019 supplied by the Spanish ‘Consorcio de Compensación de Seguros’. Flood losses are aggregated by postal codes. Fluvial flood losses in the Pamplona metropolitan area have been estimated for the set of synthetic hydrographs and resulting flood maps. The results show that while flood losses are expected to decrease in the future for low return periods (2-50 years), they are expected to increase for high return periods (100-1000 years). This suggests that precautionary measures will play an important role to reduce residual risk.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022864

Year: 2022