Assessing the impacts of urbanization on flooding using WRF-Hydro, a process-based hydrological modeling system

Abstract:

Urban flooding is a rising source of economic loss and social disruption throughout the world and much of the United States. In California – where 95% of the population resides within urban areas – flood risk is growing and threatening key systems and infrastructure, due in part to climate change and extreme weather events outside the range of past experiences. In this context, the management of flood risk requires an advanced understanding of urban hydrologic and land surface processes to implement appropriate adaptive measures at a city scale. Building on the WRF-Hydro modeling system, we develop a physics-based integrated hydro-climate modeling framework over a highly developed urban watershed in Los Angeles, California. The model is used to predict the spatial distribution of flood depth and velocity under different scenarios of urban development and extreme precipitation. Simulations are based on high-resolution representation of urban topography and land use, which are pre-processed in a Geographic Information System to reflect urbanization within the model structure. This study not only highlights how historic patterns of development have played a role in exacerbating flood risk, it also provides insight for future flood risk management and adaptation planning. While the research can help decision-making in Los Angeles, the relevance of its findings is also discussed within the larger global context of flood management in cities.