Hydrological-hydrodynamic modeling of climate-induced urban flooding of design storms using HydroPol2D: a case study in São Carlos, Brazil

Under scenarios of climate change, the frequency and intensity of urban flood events are expected to increase, leading to more severe impacts in cities. Thus, coupling spatially distributed hydrological and hydrodynamic models is essential to simulate flood propagation and identify flood-prone areas in urban basins. This study aims to evaluate the influence of extreme rainfall events on flood dynamics in the urban basin of São Carlos, under both current climatic conditions and future projections derived from climate change scenarios (ETA-MIROC5 for RCP 4.5 and 8.5, 4.5 W/m2 and 8.5 W/m2). To examine how rainfall influences flood propagation and the extent of inundation, the two-dimensional, fully distributed hydrological-hydrodynamic model HydroPol2D is applied. This model solves the conservation equations for momentum, mass, and pollutant transport over a Cartesian grid. This methodology is used in selected urban catchments of São Carlos (SP) - Brazil, a city recognized as a technological hub in Brazil that suffers from episodes of intense rainfall and subsequent flooding. These events continue to cause recurring crises, resulting in both material and immaterial losses. The results revealed that, on average, flooded areas increased by 65% compared to current conditions. Moreover, for 100-year return period events, maximum flood depths increased by up to 2.5 meters in certain locations within the basin.