Estimating the Impact of Urban Space Competition on Flood Risk: Case Study of the Lanzhou Reaches of Yellow River, China

Abstract

As a result of global urbanization, urban areas are being replaced by single developed areas and urban water space is also inevitably occupied. Disruption of the balance between land for construction and water space, combined with global climate change, causes cities to face more uncertain flood risks. In this study, the one-dimensional hydrologic model was used to simulate the large-scale urban river flood scenarios in Lanzhou, a city in the interior of Northwest China. Flood intensity maps were drawn based on the simulation results to analyze the urban flood risk under the context of space competition between people and water. The study indicates that the topographic vulnerability of the built-up area that was transformed from water bodies and floodplains does not disappear. Rather, structural measures which limit water to flow within a given space and protect people from the flooding increase flood risk. Urban flood risk depends on the extent of water space being exploited and occupied. The theoretical and practical significance of these results for urban planning, flood protection, and early risk warning are discussed.