The Conceptual Discussion of Precipitation-Runoff Characteristics and Retention/Detention Response in The Watershed

With urbanization and climate change, the existing flood control facilities cannot manage the excess runoff as well as before. Therefore, the source-oriented flood abatement measure and integrated flood management have recently been promoted by many countries. However, only few studies can offer underling theories for these measures. Therefore, we first study the convolution method with instantaneous unit hydrographs (IUH) for the rainfall-runoff computation process to propose the runoff contribution concepts and then obtain the analytical solutions to resulting runoff under different rainstorm conditions. Through these results, we could propose conceptual theories of flood management in order to create a more effective way to utilize flood control facilities and renovate the watershed. To sum up, we investigated the conceptual theory of flood management by following topics: (1) the runoff contribution concept, (2) the rainfall-runoff characteristic analysis, (3) the critical storm duration and the runoff control strategy, (4) the implementation suggestion of the retention and detention to reduce the possible maximum flood discharge, and (5) the watershed improvement suggestion to reduce the possible maximum discharge during different events. According to our findings, the runoff contributed by specific watersheds is actually dependent on the amount of its area and the travel time to the outlet. Moreover, the effect of detention/retention basin relies heavily on the peak time of rainstorm, hence this parameter should be the priority consideration while making the implement decisions of these flood control facilities.