土石流發生頻度之研究-以陳有蘭溪流域為例

Evaluation on the Occurrence Frequency of Debris Flow in Chenyulan River Watershed

陳曉貞(Hsiao-Chen chen)

指導教授 ： 曾志民

長榮大學/管理學院/土地管理與開發研究所/碩士(2007年)

https://doi.org/10.6833/CJCU.2007.00133

摘要

土石流發生頻度定義為一溪流於某幾次颱風暴雨事件中累計發生土石流次數與總事件數之比值，其值介於0~1之間，發生頻度值愈高即代表該溪流發生土石流之次數愈頻繁。
本研究以陳有蘭溪流域一級河序之117條溪流為分析對象，利用SPOT衛星影像加以判釋溪流於桃芝颱風與敏督利颱風期間之土石流發生記錄。文中選定有效集水面積、溪流平均坡度、集水區平均坡度、集水區形狀係數、潛在崩塌比、岩體品質評分（RMR）值等6個為與時間無關之靜態因子，以及與時間有關之新增崩塌率共7個因子作為分群因子，針對上述溪流進行分群。分群方法係以模糊分群法將屬性相近之溪流分為一群，並以隸屬函數表示各溪流隸屬各群別之程度。分群結果透過Wilk’s λ值及土石流災害記錄檢驗群體差異度，顯示包含動態因子之分群能使群體間具有較顯著的差異程度，其中桃芝颱風期間之群體土石流平均發生率分別為0.7、0.44及0，敏督利颱風期間則為0.36、0.21及0。
此外，本研究分析不同土石流發生頻度溪流之地文及水文特性顯示，主導土石流發生頻度高低之關鍵因素，靜態方面以坡度因子、地質岩性以及有效集水面積等為關鍵；而動態方面之新增崩塌率亦有顯著之影響性。依據土石流發生頻度、新增崩塌地及颱風事件降雨之空間分布進行比對，發生頻度高者具有較集中的降雨量及土砂供應量。至於陳有蘭溪流域易重覆發生土石流災害之地點，則以神木、信義及龍神橋等地區為主，因此這些地區應加強防救災系統及颱風豪雨期間之即時監控。

關鍵字

土石流 ； 發生頻度 ； 模糊分群 ； 陳有蘭溪流域

並列摘要

Occurrence frequency of debris flow for a stream, in this study, is defined as the ratio of it’s occurred frequency to total numbers of debris flows during several storms or typhoons. This ratio value is between zero to one and when it closes to one, it means the stream has higher potential to occur debris flow.
　　117 streams of Chenyulan river watershed and records of debris flow occurrence are analyzed, which are judged by SOPT images between Toraji typhoon and Mindulle typhoon. Cluster those streams by fuzzy c-means methods (FCM) according to 6 static geographic factors and 1 dynamic time factor, which are effective watershed area, average slope of gullies and watershed, shape factor of watershed, potential landslide ratio, or Rock Mass Rating (RMR) and extended landslide ratio, respectively. Then, examine the difference of clusters by Wilk’s λ value and above records. As a result of clustering, the clusters show more obvious variation only including of dynamic factor, which the mean ratio value of debris occurrence in period of Toraji typhoon for three cluster is 0.7, 0.44 and 0, respectively; it is 0.36, 0.21 and 0 in period of Mindulle typhoon, respectively .
　　In addition, not only the static of effective watershed area, average slope of gullies and watershed, and RMR are the key to domain the value of occurrence frequency of debris flow, but also the dynamic factor of extended landslide ratio is. Furthermore, compare with distribution of rainfall events. It also shows that the stream which is evaluated as higher value have more concentrated rainfall and a lot of sediment materials. For instance, it takes place at Shen-mu, Shin-yi and Lun-shen regions in Chenyulan river watershed, and those are suggested to enhance precaution and monitor in future storms or typhoons.

並列關鍵字

debris flow ； occurrence frequency ； fuzzy c-mean methods ； Chenyulan River watershed

參考文獻

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