Evaluating the Rainfall Storage Effect of Low-laying Paddy Area by Runoff Analysis Using Discharge Rate from Paddy Field Outlet with Notch for Outflow Control

Abstract

  This study aims to quantify the rainfall storage effect of paddy fields during a flood, using runoff analysis with discharge rate data from an outlet with a notch for outflow control. The study site is located in the low-lying paddy area in the Chikugo basin. To quantify the flood mitigation capacity of the paddy field, outflow rate from the outlet of the paddy field was estimated and rainfall runoff analysis was conducted during actual inland flooding periods. Using the Radar AMeDAS Rainfall as model input data, spatial distribution of the rain in the study site was analyzed. To study spatial distribution of flood mitigation capacity, the object area was divided into 36 sections mesh of 1 km² and rainfall storage effect was quantified for each section. By calculating outflow over the paddy field notch, time variation of rainfall storage discharge was identified and the relationship between precipitation and flood mitigation capacity of paddy field was clarified. Additionally, division of the drainage basin into the Radar AMeDAS Rainfall data led to an improvement in the analysis precision of flood mitigation in the whole target district.