Hydrological impact of blueprinted flood retention lakes in a rural-urban catchment

Abstract

Rural-urban catchments are susceptive to flood nowadays in the context of climate change and urbanization. To cope with this situation, flood retention lakes (RLs) are increasingly employed. However, the dynamic influence of RLs on local hydrology, as well as the joint effects of multiple RLs with different geographic configurations are not clear. Thus, this study aims to model and evaluate how RLs affect catchment flooding processes, particularly considering the geographic relations of potentially blueprinted RLs in future development. A 2D hydrodynamic model is developed for the upper Shenzhen River Basin and calibrated with streamflow in a gauge station against typical flood events. Various storm events are designed with wide ranges of intensity and duration, and flood responses are modeled for both current and blueprinted situations. Results show that the as-built RL can be satisfactorily effective for events with moderate exceeding frequencies (5-50 year) and short durations (6 hours or less). Additional RLs are blueprinted based on preliminary simulation results as well as land use conditions to further reduce the maximum surface inundation and peak runoff on top of the current layout. The series connection shows slightly better capability viewed along the river channel, while the parallel connection can provide benefits to sub-watersheds. The distributed setting has a better overall performance compared to the aggregated setting with the same total capacity, with a larger area of maximum inundation reduction. The downstream control RL configurations tend to perform better for moderate events while the upstream ones are superior for more extreme events.