A Study on the Slopeland Disaster of the Malun Stream Watershed in Yilan County

• Main Authors: CHIH-CHENG CHEN, 陳智誠
• Other Authors: Bang-Zhu SHI
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/7awbg6

碩士 === 國立臺北科技大學 === 土木工程系土木與防災碩士班（碩士在職專班） === 103 === This case is based on Yilan County Malun stream watershed as a study subject based on the three recent typhoon incidents, typhoon Parma (2009), typhoon Megi (2010) and typhoon Saola(2012) to analysis the rainfall averages, frequecy of rainfall and landslide scale to investigate and analysis the earth and sand and water management calculations. Due to the collapse of the Malun stream catchment area has reached to +5.9% of the total catchment area, when typhoon arrives the heavy rainfall caused the earth and sand threaten the prevention and the security to the 2 tribes of downstream Malun bridge and Dong Die village. Through the analysis showing that due to the typhoon incident has brought out the earth and sand and rainfall runoff, suggest to close the bridge and necessary evacuation. The study shows the rainfall frequency of Malun stream one day storm frequency in 2 years has reached to 382.8mm, 5 years 591.5mm, 10 years 727.2mm, 20 years 855.6mm, 25 years 896.0mm, 50 years 1019.4mm, 100 years 1140.7mm, 200 years 1260.5mm, the landslide area raised from 20.92 ha to 131.63 ha, the landslide variant quantities raised from 147,860m3 to 916,220m3. When one day storm volume reached to 840.5mm, Malun bridge is sufferring from the bury risk and it needs to be closed. At the moment, if the landslide scale, earth and sand quantities and yearly rainfall frequency reach to 20 years may bring the risk of lifting the earth and sand and break the Malun bridge. Through the three typhoon incidents , the analysis shows the rainfall volumn, runoff, landslide, earth and sand output and migration are nearly to the earth and sand cleanout volumm. From the past 3 years earth and sand cleanout volumn and the maximum of one day storm volumn&;#39;s correlations very reached , thus from now on a day after typhoon incident the maximun storm volumn can be used as basis of the cleanout volumn. Meantime, analysis mode can be adopted and used along as HEC-RAS and FLO-2D to increase the result of analysis accuracy and can be used as evaluate the soil sand cleanout basis.