Effects of Duration and Time Distribution of Probability Rainfall on Paddy Fields Inundation

The objective of this study was to analyze the effect of the duration and time distribution of probability rainfall on farmland inundation for the paddyfields in the drainage improvement project site. In this study, eight drainage improvement project sites were selected for inundation modeling. Hourlyrainfall data were collected, and 20- and 30-year frequency probability rainfalls were estimated for 14 different durations. Probability rainfalls weredistributed using Intensity-Duration-Frequency (IDF) and Huff time distribution methods. Design floods were calculated for 48 hr and critical duration,and IDF time distribution and Huff time distribution were used for 48 hr duration and critical duration, respectively. Inundation modeling was carriedout for each study district using 48 hr and critical duration rainfalls. The result showed that six of the eight districts had a larger flood discharge usingthe method of applying critical duration and Huff distribution. The results of inundation depth analysis showed similar trends to those of design floodcalculations. However, the inundation durations showed different tendencies from the inundation depth. The IDF time distribution is a distribution inwhich most of the rainfall is concentrated at the beginning of rainfall, and the theoretical background is unclear. It is considered desirable to applycritical duration and Huff time distribution to agricultural production infrastructure design standards in consideration of uniformity with other designstandards such as flood calculation standard guidelines.N