Estimating peak flow of Farahzad River in Tehran under climate change and debris flow scenarios: A novel approach and its implications for urban flood hazard mapping

Abstract

Urban river flooding is a serious threat to cities that have altered their river buffer zones due to urbanization and climate change. This study aims to estimate the peak flow of urban rivers by considering the effects of climate change and debris flow on flood hazard. A novel approach is proposed that integrates hydrological, sedimentological, and hydraulic method and models to account for the influence of sediment volume, woody debris, and culvert blockage on peak flow estimation and flow parameters. The approach is applied to the Farahzad River basin in Tehran, Iran, using future data downscaled from a global climate model under the RCP8.5 scenario for 50- and 100-year return periods. The results show a significant increase in the peak flood discharge by nearly 3.2 times, the flood zone by 10–20%, the flood velocity by 15–30%, and the inundation depth by 10–40% due to climate change and debris flow scenarios. The study demonstrates the importance of considering multiple factors in estimating the peak flow of urban rivers and provides a useful tool for urban flood risk management.