玉峰溪集水區崩塌特性與崩塌體積之探討

The Characteristics of Landslides and Landslide Size in Yu-Fong River Watershed

10.29417/JCSWC.201009_41(3).0003

陳樹群(Su-Chin Chen)；翁愷翎(Kai-Ling Weng)；吳俊鋐(Chun-Hung Wu)

崩塌深度 ； 崩塌量估算 ； 石門水庫集水區 ； 玉峰溪 ； landslide depth ； landslide volume ； Shihmen reservoir watershed ； Yu-Fong watershed

中華水土保持學報

41卷3期（2010 / 09 / 01）

217 - 229

繁體中文

本研究主要探討玉峰溪集水區崩塌地貌特性、誘發特性及崩塌量之估算，根據本研究以2006年正射影像圖所萃取出之601處崩塌地案例進行分析，總崩塌面積164.3公頃，崩塌率約1.9%。玉峰溪集水區之崩塌具有幾個地貌特性，58.2%之崩塌地面積大於0.5ha，82.4%崩塌地屬於狹長型崩塌地（長寬比大於1），78.4%崩塌地位於易崩之澳底層，89.4%之崩塌地坡度介於30°至50°，玉峰溪集水區崩塌分佈以下邊坡或山腰地區爲主，崩塌前後之崩塌坡面型態山直坡轉爲直坡及凹坡爲主。而在道路開發、河川分佈及降雨等三項誘發因素探討上，分析結果顯示僅有35.4%之崩塌地位於道路上；50.6%之崩塌地位於河川兩岸，且位於河川兩岸的崩塌案例，其平均崩塌面積較非未於河川兩岸之崩塌案例平均面積約大兩倍；78.5%崩塌案例位於颱風事件中累積降雨量超過1000mm區域。本研究認爲玉峰奚集水區主要崩塌誘發因素以豪雨及洪水淘刷坡腳爲主。在崩塌體積估算上，本研究推導崩塌面積A(下標 L)(平方公尺)刁及崩塌體積關係式V(立方公尺):V=0.015A(下標 L)^1.606，相關係數達0.83、可供未來估算土砂產量之使用。

The study discusses the geomorphological and inducing characteristics of the landslides as well as the estimation of landslide volume in the Yu-Fond creek watershed. The 601 landslide cases with a total area of 164.3 ha and a landslide ratio of 1.9% were extracted from aerial photographs in 2006 and used for analysis in this study. The geomorphological characteristics of landslides in the Yu-Fong watershed are explained in the following. Landslides with an area of ＞0.5 ha with a long and narrow shape make up 58.2% and 82.4% of all landslide cases, respectively. The landslides located in the Aoti formation, the landslide-prone formation, and in the hillslope with a slope of 30°-50°, make up 78.4% and 89.4% of all landslide cases, respectively. The landslides mainly occurred in the middle or lower hillslope. The major morphology of the slope in the landslide cases were plain types prior to the landslide, and plain and concave types following the landslide. The inducing characteristics of landslides in the Yu-Fong watershed are explained as follows. About 35.4% and 50.6% of landslides occurred along roads and rivers, respectively. The area of the landslides located along the rivers was about twice as large as those not along the rivers. About 78.5% of landslides occurred in heavy rainfall areas, i.e. an accumulated rainfall of ＞1,000 mm during the typhoon events. This study suggests the dominant factors in Yu-Fong watershed are heavy rainfall and river-scouring. This study also derives the estimation formula for the landslide area AL (m^2) and landslide volume V (m^3): V=0.015 AL 1.606 with an R2 of 0.83. The formula can be used for estimating sediment yield in the watershed.