降雨成因を考慮した降雨の時空間分布特性の統計的解析

Abstract

Recently in Japan, especially in very urbanized area, a small or middle size river (the catchment size is about less than 200 kin2) is confronted with the danger of flooding because of its short run-off time and high run-off ratio.But in river planning, it is not so easy to deal with these rivers.This is mainly due to two reasons; (1) run-off mechanism in urbanized area is very complicated because of the sewerage system (2) heavy rainfall sometimes occurs in small area and short time, so the characteristic of time and space distribution of rainfall is not well known.In this paper we study about the the time and space distribution of rainfall in urbanized area around Osaka using the data of rader raingage.We first categorize rainfall data into four types; typhoon, frontal, low and thunder rainfalls.Then for each rainfall type we analyze the DAD (duration, area and depth) of rainfall and calculate the orientation of rainfall field and shape ratio (the ratio of major axis to minor axis) assumig the shape is an ellipse.And we also apply the cluster analysis to divide rainfalls into a few typical types of group using the result of DAD analysis.