Exploring the impact of urbanization on flood characteristics with the SCS-TRITON method

Urbanization is one of the main factors altering hydrological processes. To understand the influence of urbanization on flood characteristics including runoff, inundation and streamflow, it is essential to quantify the level of urbanization and analyze the corresponding impacts on flood. This study proposed an integrated and systematic framework to assess how urbanization affects flood characteristics in Hangzhou, China. Land use changes in 2000–2020 representing the level of urbanization were extracted from Landsat images with an ensemble machine learning method and future scenarios were designed with Patch-generating Land Use Simulation (PLUS). The runoff, inundation and streamflow under 24 h design rainfall with 100 year return period were assessed using the integrated hydrologic-hydraulic model for land use of different years. Finally, the relationship between land use changes and flood characteristics were identified and analyzed. It was found that the study area underwent a rapid urbanization process with artificial surface increasing from 6.93% to 29.12% during 2000–2020. Total runoff volume and total inundation volume showed a growing trend with a percentage change of 5.96% and 12.33% respectively under the design rainfall. This study highlights the significance of water body area in influencing flood characteristics. The results of this study can improve understanding of flood responses to land use and provide useful insight to decision makers in developing urban flood management measures.