Rational Evaluation of Flow Rate by Rainfall Considering Flood Arrival Time in Yamato River Basin under Climate Change

Conventional flood control plans have evaluated flow rate based on average rainfall over watershed without considering space-time distribution, and thus the correlation between rainfall and flow varies. This study aims to reasonably evaluate flow rate in response to rainfall, and presents the results of a study to solve the problem of conventional flood control by setting rainfall that takes into account flood arrival time in the Yamato River system, a first-class river.A distributed runoff model was used in the analysis, and a large ensemble climate projection data (d4PDF-RCM) was used as input to analyze the flow rate under climate change. Next, calculate the average rainfall over watershed using the conventional method and the method proposed in this study, which takes into account the flood arrival time, and was compared in correlation with the flow rate. The results showed that the proposed method produced a clearer correlation, but the correlation was weaker than that of the conventional method and was not sufficient to estimate runoff from rainfall.