DISTRIBUTION AND CHARACTERISTICS OF FREQUENT INLAND WATER INUNDATION AREAS IN WAKAYAMA CITY, JAPAN

Abstract

 The purpose of this study is to clarify the characteristics of inland water inundation in Wakayama City, Wakayama Prefecture, based on past inundation records. We created a GIS database of flood-damaged area maps that recorded historical inland water inundation records for the past 25 years and extracted frequent inland water inundation areas where inland water inundations have occurred more than three times in the past. As a result of the time-series analysis of frequent inland water inundation areas, it was found that the number of frequent inland water inundation areas has been increasing. The results of the analysis of the causes of inland water inundation show that the influence of Anthropogenic and meteorological causes has increased in recent years. In the increase of the Anthropogenic factors, there are two land-use changes cases: (1) the number of paddy fields in the vicinity of frequent inland water inundation areas has decreased, resulting in a decrease in the retarding capacity of rainfall at paddy fields, and thus the direct flow of rainfall (inland water) into the frequent inland water inundation area, and (2) the overall decrease in the number of paddy fields around frequent inland water inundation area has caused a flow of inland water that exceeds the retarding capacity of the paddies in the vicinity of the frequent inland water inundation area.