산지형 하천의 토양침식 및 토사유출량 산정

Abstract

Jeju island, which is located along the moving path of typhoon that heads north, is an island that suffers from flooding and overflow by torrential rain often, and the streams of Jeju island are mountainous streams whose slope is steep and length is short, so with abrupt effluence occurring, damages of downstream farm field and shore culturing farms are increasing. For countermeasure for torrential rain damages of Jeju island, framework plans for stream maintenance are established or detention ponds are designed emphatically, so analyses and preventive measures of sediment yield are insufficient. Also, in existing studies that estimated sediment yield, only basic unit method or particular value of basin is used, so they are not suitable to deduce value appropriate for basic characteristics. In this study, Oaedo stream one of the mountainous streams of Jeju island was selected as the basin of study subject and was classified into 3 sub-basins, and after the characteristics of subject basin, the soil erosion amount and the sediment delivery of the stream by land usage distribution were estimated with the use of SATEEC(Sediment Assessment Tool for Effective Erosion Control) ArcView GIS, the sediment yield amount of 2000 and 2005 were analyzed comparatively. As a result of estimating the sediment yield amount of 2000, the total soil erosion amount was estimated as 601,882 tons/year, and particularly the average soil erosion amount per unit area of sub-basin 2 was found the highest. The sediment yield amounts of the three sub-basins in consideration of sediment delivery ratio were respectively 12,572.7, 14,080 and 157,761 tons/year, and though the sediment yield amount of sub-basin 3 was the most, the sediment yield amount per unit area was found small compared with other basins if the small sediment delivery ratio considered. The total soil erosion amount of 2005 was found to be 950,960 tons/year, and sediment yield amounts were estimated as 35,172.9, 5,266 and 258,535 tons/year respectively. The soil erosion and sediment yield amount per unit area was highest in sub-basin 1 and the lowest in sub-basin 2. The soil erosion and sediment yield amount of 2005 using single storm rainfall were estimated high compared with 2005, but for sub-basin 2, the values rather decreased due to change in land usage, and the land coverage of 2005, since there are many classification of land usage compared with 2000, enabling to reflect more accurate land usage condition, could deduce appropriate results. It is anticipated that such study results can be utilized as basic data to propose direction to predict the amount of sediment yield that causes secondary flooding damage and deteriorates water quality within detention pond and grit chamber, and take action against damages in downstream farm field and shore culturing farms.