Peak discharge mitigation effects in different rainfall patterns at a paddy plot with a runoff control plate

Abstract

Study regionTawaramoto Town, Nara Prefecture, Japan Study focusIn Japan, steep topography and humid climate make the country vulnerable to flooding and the importance of the flood mitigation function of rice paddy fields has been emphasized. The ‘paddy field dam project’ is being promoted to enhance the flood mitigation function by installing a runoff control plate in a drainage box. However, there are a few studies that have examined the effects of differences in rainfall patterns and rainfall intensity on the function of paddy field dam by examining possible future rainfall patterns. We generated simulated rainfall patterns from the probability-rainfall intensity formula and from the stochastic analysis of historical rainfall data. For each rainfall scale, we investigated the relationship between rainfall characteristics and the function of the runoff control plate. New hydrological insightWhen different rainfall patterns simulated using stochastic methods were input to the model, the peak ponding depth, and difference in peak ponding depth compared to paddy plot without runoff control plate might be larger than when the unimodal rainfall with the almost same 24-h rainfall were input. If the rainfall scale and hourly peak rainfall are determined, we can estimate the possible range of the peak discharge mitigation rate and the difference in the peak ponding depth between the plot with and without the runoff control plate.