Jeju island, which is located along the moving path of typhoon, suffers from flooding and overflow by torrential rain. So abrupt runoff occurring, damages of downstream farm field and shore culturing farms are increasing. In this study, Oaedo stream, one of the mountainous streams on 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 ArcView GIS, the sediment yield amount of 2000 and 2005 was analyzed comparatively. As a result of estimating the sediment yield amount of 2000, the three sub-basins were respectively 12,572.7, 14,080 and 157,761 tons/year. and sediment yield amounts were estimated as 35,172.9, 5,266 and 258,535 tons/year respectively in 2005. The soil erosion and sediment yield amount of 2005 using single storm rainfall were estimated high compared with 2000, but for sub-basin 2, the values rather decreased due to changes in land use, and the land coverage of 2005, since there are many classifications 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 a 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 the downstream farm field and shore culturing farms.

In this study, compared with the result of water surface elevation and water velocity on the establishment of river maintenance basic plan and result of HEC-GeoRAS based GIS, and after use the result of water surface elevation and velocity were observed in the Han stream on Jeju island, analysis 2 dimensional stream flow. the lateral hydraulic characteristics and curved channel of the stream were analyzed by applying SMS-RMA2 a 2 dimensional model. The results of the analysis using HEC-RAS model and HEC-GeoRAS model indicated that the distribution ranges of water surface elevation and water velocity were similar, but the water surface elevation by section showed a difference of 0.7～2.18 EL.m and 0.63～1.16 EL.m respectively, and water velocity also showed differences of maximum 1.58m/sec and 2.67m/sec. SMS-RMA2 analysis was done with the sphere of Muifa the typhoon as a boundary condition, and as a result, water velocity distribution was found to be 1.19 through 3.91 m/sec, and the difference of lateral water velocity in No. 97 through 99 the curved channel of the stream was analyzed to be 1.59 through 2.36 m/sec. In conclusion it is anticipated that the flow analysis of 2 dimension model of stream can reflect the hydraulic characteristics of the stream curved channel or width and shape, and can be applied effectively in the establishment of river maintenance basic plan or management and designing of stream.