降雨對太麻里溪集水區土砂產量影響之探討

Effects of Extreme Rainfalls on Sediment Yield of Taimali Creek Watershed.

潘晨綱(Chen-Gang Pan)

指導教授 ： 許中立

國立屏東科技大學/工學院/水土保持系所/碩士(2010年)

https://doi.org/10.6346/NPUST.2010.00219

摘要

台灣平均年降雨量為2510mm，約為世界平均值的2.6倍，78%降雨量集中在雨季，且多數降雨來自颱風之極端降雨，加上近年來全球氣候變遷問題日益嚴重，造成台灣集中降雨的特性更為顯著，如2009年莫拉克颱風挾帶的驚人雨量，頻頻改寫歷史降雨新高，而這些碩大的降雨造成山區嚴重的土石崩落，對下游地區人民生命財產安全有莫大之威脅。本研究利用極端降雨資料推求合適之打荻氏公式，並由崩塌深度推估式來推估合理之崩塌地平均深度，進而探討集水區於降雨事件後之新增崩塌量，期能提供相關單位日後治理規劃之參考。本研究結果顯示以定義1%之平均極端降雨，所求得之打荻氏公式較能精準之推估，其平均誤差率為5%；利用坡度深度法所推估的崩塌地平均深度，較能代表整體崩塌地的平均深度，其值為8.8m，與前人所推估之深度有3.3m之差異，研判此差異為高降雨所造成；將打荻氏公式所推估之新增崩塌面積與平均崩塌深度相乘，求得之新增崩塌土砂量有低估之情形，咎其原因為忽略了原崩塌地之產砂能力所致。

關鍵字

極端降雨 ； 崩塌 ； 土砂產量 ； 打荻氏公式

並列摘要

The average annual rainfall in Taiwan is 2510 mm, and it is 2.6 times the world average. With 78% of the rainfall concentrated in the rainy season, most rainfall from the extreme rainfall of typhoon, and the growing problem of global climate change in recent years, the concentrated rainfall in Taiwan is a significant feature. The 2009 Typhoon Morakot, for instance, was found to rewrite the history of maximum rainfall again. The huge precipitation would result in critical debris avalanche and seriously endanger downriver people's lives and property. Hence, the current research was aimed to probe into the increased volume of collapse after raining for the precipitation area by utilizing the data of extreme rainfall to deduce the appropriate Daogi formula to further figure out a reasonable equation to estimate the average depth of the collapse.
The results exhibited that the definition of 1% to the average of extreme rainfall for the Daogi formula, with the average error rate of 5%, would obtain more accurate estimation than others. It was also found that the average depth of the landslide by use of the gradient depth calculation would represent the overall average depth of the landslide. The value 8.3m was discordant in contrast with the previous study by the depth of 3.3m difference. This phenomenon might be due to the high rainfall. Moreover, the findings revealed that the increased volume of collapse sediment yield deduced from Daogi formula, which was derived from the increased volume of collapse area multiplied by the average depth of collapse, was underestimated. This underestimation could be ascribed to the neglect of the capacity of sediment yield in the original collapse area.

並列關鍵字

Extreme Rainfall ； Landslide ； Sediment yield ； Daogi formula

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