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Title: 降雨誘發崩塌侵蝕之規模頻率及其控制因子
Magnitude-frequency of Rainfall-triggered Landslide Erosion and its Controls
Authors: 陳毅青
Contributors: 地理學系
Keywords: 崩塌侵蝕;極端降雨;規模與頻率;崩塌產砂量;莫拉克颱風
Landslide erosion;Extreme rainfall;Magnitude-frequency;Landslide volume;Typhoon Morakot
Date: 2012
Issue Date: 2015-04-29T04:08:19Z
Publisher: 國立台灣大學
Abstract: 崩塌侵蝕為台灣山地集水區重要之邊坡作用與河川泥砂主要來源,因此,釐清崩塌侵蝕的規模-頻率以及控制因子,將有助於災害防治、集水區土砂管理與地形演育之研究。本研究以多時序山崩目錄與體積-面積關係式,量化高屏溪、曾文水庫與石門水庫集水區2001-2009年24 場降雨誘發之崩塌體積與侵蝕量,探討降雨和集水區地文特性對侵蝕量的影響,並透過水文頻率分析來模擬崩塌規模-頻率的關係。
研究結果顯示,2009年莫拉克颱風在高屏溪流域產生534.25±39.37 Mm3的崩塌體積,等同於186.28±13.73 mm的侵蝕量,此侵蝕量相當於該集水區約24年的總侵蝕量以及地震矩規模Mw = 7.7~7.8大地震產生的崩塌體積,顯示台灣的極端降雨與大規模地震皆為崩塌侵蝕的重要驅動力。其次,岩石單壓強度與不連續面密度導致集水區主要崩塌材料類型分布的差異,石門水庫集水區岩石強度較強,以淺層的土壤型崩塌為主,並受到短延時降雨主控;在高屏溪與曾文水庫集水區岩石強度較弱,以深層底岩-土壤混和型崩塌為主,並受到長延時降雨所主控,導致南部地區的侵蝕量比北部高出5~13倍。綜合降雨和集水區地文因子,本研究提出以崩塌規模尺度整合不同地文特徵之集水區崩塌侵蝕為崩塌侵蝕的量化指標。最後,由崩塌規模-頻率分析推估高屏溪流域平均侵蝕率為2.99~5.27 mm yr-1,其中極端且高強度的降雨對於崩塌侵蝕的作用大於頻繁且低強度的降雨。尤以重現期50年以上的極端降事件,佔長期崩塌侵蝕的54~74%。但是極端降雨卻會造成推估長期崩塌侵蝕率時,產生至少±1.2 mm yr-1的不確定性。本研究發現極端降雨為台灣集水區崩塌侵蝕之重要驅動力,所以研究長期集水區侵蝕率估算時,應考慮極端事件造成的崩塌規模與頻率。
Landslide erosion is a dominant hillslope process and the main source of stream sediment in tropical, tectonically active mountain belts. The purposes of this study are quantifying rainfall-triggered landslide erosion, as well as investigating their controls and magnitude-frequency patterns. We quantified the amounts of landslide erosion triggered by 24 rainfall events from 2001-2009 in the Kaoping River, Tsengwen Reservoir, and Shihmen Reservoir watersheds in Taiwan by using multi-temporal, event-based landslide inventory and volume-area scaling relationships. The results show that landslide erosion caused by Typhoon Morakot is 534.25�39.37 Mm3 or 186.28�13.73 mm which can be of comparable magnitude to landslide erosion caused by a magnitude MW = 7.7~7.8 earthquake or 24 years of basin-averaged erosion. Therefore, this shows that typhoon-triggered extreme rainfall and great earthquake are both critical triggers on landslide erosion in Taiwan. Also, uniaxial compressive strength and rock mass discontinuity spacing influence the domainant material type of landslide in a watershed. The deeper landslides that mobilize soil and bedrock are dominant in the south characteristized by weak rocks and are triggered by long-duration rainfall. In contrast, shallow landslides are dominant in the north characteristized by hard rocks and are triggered by short-duration rainfall. Deeper landslide mobilized soil and bedrock cause 5~13 times of erosion in the south more than that in the north. Therefore, this study proposed a landslide magnitude scale, amount of landslide erosion in an event over the erosion rate in a watershed, to cooperate the characteristic of watershed in prediction of landslide erosion. Furthermore, the magnitude-frequency analysis shows landslide erosion rate in the Kaoping River watershed is 2.99~5.27 mm yr-1. Extreme-intensive rainfall plays a more important role in hillslope mass wasting than frequent-moderate rainfall, which rainfalls with return period larger than 50 years contribute 54~74% of total landslide erosion. Magnitude-frequency of extreme rainfall can induce at least �1.2 mm yr-1 uncertainty in estimation of landslide erosion rate. In summary, extreme rainfall is critical triggers in landslide erosion. Magnitude-frequency of landslide should be considered when estimating long-term erosion rate.
Relation: 博士; 國立台灣大學土木工程研究所
Appears in Collections:[地理學系] 專書

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