高屏溪集水區土砂災害降雨特性之研究-以莫拉克颱風為例

Study on Rainfall Characteristics of Sediment Disaster in Kao-Ping Stream Watershed During Typhoon Morakot

林煥軒(Huan-Hsuan Lin)

指導教授 ： 李明熹

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.2010.00263

摘要

2009年8月莫拉克颱風挾帶豪雨侵台，造成台灣中南部地區發生嚴重的崩塌、洪水及土石流災害，死亡人數超過700人，為近年來最嚴重的颱風事件，其降雨量更打破台灣南部地區以往的紀錄。本研究採用高屏溪集水區52個雨量站，分析莫拉克颱風期間之降雨特性，包含降雨強度、累積雨量、降雨延時及重現期距，進而探討風災期間崩塌與土石流發生之降雨條件。
研究結果顯示，莫拉克颱風為高屏溪集水區帶來高累積雨量、長降雨延時及廣區域的降雨特性，其中尾寮山雨量站在降雨延時為1小時、12小時、24小時、48小時及72小時的最大累積雨量分別為119mm、843mm、1,412mm、2,319mm及2,561mm，且降雨延時從10小時至72小時期間，該雨量站最大降雨強度的重現期距都超過200年。尾寮山雨量站在113小時內共降下2,969mm的雨量，這種破記錄的降雨條件成為觸發崩塌及土石流發生的主要因素。
莫拉克颱風後集水區崩塌率與累積雨量分析結果顯示，崩塌率隨著累積雨量的增加而有明顯上升的趨勢，當累積雨量超過2,600 mm時，崩塌率最大達到18.7%。土石流發生事件降雨條件分析結果顯示，21場土石流發生當時的平均降雨強度、平均降雨延時及平均累積雨量分別為44 mm/hr、43小時及1,000 mm，而大部分土石流發生時間落在最大降雨強度發生後的2~4小時內。

關鍵字

莫拉克颱風 ； 高屏溪集水區 ； 土石流 ； 崩塌

並列摘要

In the August 2009, Typhoon Morakot brought heavy rainfall and caused several landslides, floods and debris flows in central and southern Taiwan. The catastrophic disasters killed more than 700 people. Typhoon Morakot caused more damage than any other typhoon because of a record-breaking amount of rain, especially in Taiwan’s southern region. This paper presents the rainfall characteristics, including the rainfall intensity, the rainfall depth, the rainfall duration and the return period of the rainfall, based on the rainfall data of 52 rain-gauge stations and the rainfall conditions when the landslides and debris flows occurred in Kao-Ping stream watershed during the action of Typhoon Morakot.
The results show that the rainfall brought by Typhoon Morakot was record-breaking, not only on rainfall amount and rainfall duration but also on total area covered with high rainfall in Kao-Ping stream watershed. The maximum 1-hour, 12-hour, 24-hour, 48-hour, and 72-hour rainfall at Weilianshan station were 119 mm, 843 mm, 1,412 mm, 2,319 mm, and 2,561mm, respectively. The estimated return periods from 10-hour to 72-hour the maximum rainfall intensity at Weilianshan station during Typhoon Morakot well exceeded 200 years. In total, 2,969 mm of rain fell at Weilianshan station over a period of 113 hours during Typhoon Morakot. This record-breaking rainfall played a major role in triggering landslides and debris flows.
The rainfall depth and landslide rates in the watershed have been analyzed after Typhoon Morakot. The results show that the landslide rates have an increasing trend with rainfall depth. The maximum landslide rate is 18.7% with rainfall depth over 2,600 mm. Twenty-one debris flow events induced by the heavy rainfalls brought by Typhoon Morakot in the watershed were analyzed. The results show that the average rainfall intensity, rainfall duration, and rainfall depth that triggered debris flows in the watershed were 44 mm/hr, 43 hours, and 1,000 mm, respectively. Most debris flows caused by Typhoon Morakot generally occurred at 2 to 4 hours after the maximum hourly rainfall intensity in the watershed.

並列關鍵字

Typhoon Morakot ； Kao-Ping stream watershed ； debris flow ； landslide

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