溪頭地區激發土石流災害臨界降雨量之研究

Rainfall Threshold Value of Debris Flow Disaster in the Sitou Region

張振生(Cheng-Sheng Chang) ； 魏聰輝(Tsong-Huei Wey) ； 賴彥任(Yen-Jen Lai) ； 陳信雄(Hsin-Hsiung Chen)

《中華水土保持學報》 41卷4期 (2010/12) Pp. 362-371

https://doi.org/10.29417/JCSWC.201012_41(4).0008

摘要

本研究蒐集溪頭地區1987年至2007年止，歷次颱風及梅雨大於200mm之大豪雨事件，對照溪頭試驗集水區量水堰留存之水位紀錄，分析激發土石流危害時，量水堰逕流峰流量，以洪峰之發生時間，推算激發土石流之累計雨量、降雨時數等統計值。結果顯示1999年九二一震災前，激發土石流之累計雨量達602.0mm、降雨時數爲23.6小時，逕流峰流量爲21.52立方公尺s^(-1)。震災後，累計雨量僅278.2mm、降雨時數爲8.8小時，即已激發土石流危害。隨時間之進程，九二一震災所產生的土石料源經多次大豪雨之搬移而減少或漸趨穩定，至2007年激發土石流之累計雨量已提高爲308.0mm、洪峰流量爲15.05立方公尺s^(-1)。

關鍵字

土石流危害 ； 臨界雨量 ； 溪頭地區

並列摘要

This study analyzed the hyetograph of debris flow using runoff data recorded at Sitou experimental watershed weir, and the torrential rain of over 200 mm occurring during typhoons and monsoon cyclones from 1987 to 2007 in the Sitou region of central Taiwan. The runoff peak time was analyzed to estimate the disaster triggering time, cumulated rainfall thresholds, and total rainfall times. The results showed with the cumulated rainfall threshold of 602.0 mm, rainfall time of 23.6 hours, and runoff of 21.52 m^3s^(-1), the debris flow would be triggered before the great earthquake on September, 21, 1999 (921 earthquake). After 921 earthquake, the cumulated rainfall threshold changed to 278.2 mm, and rainfall time of 8.5 hours. With time, the sediment yield from the 921 earthquake disaster decreased and gradually stabilized due to the removal by numerous meteoric rainstorm events. In 2007, the rainfall thresholds that could trigger debris flow was elevated to 308.0 mm and runoff had changed to 15.05 m^3s^(-1).

並列關鍵字

Debris flow disaster ； rainfall threshold value ； Sitou region