支流土石流造成主支流交會處堰塞湖之地貌變化：現地調查及實驗

Abstract

本篇論文以現地調查配合實驗探討主支流匯流處土石流與主流形貌之關係，我們將重點放在荖濃溪與其支流布唐布納斯溪交匯處，此地區在2007年及2011年出現過堰塞湖，2009年莫拉克颱風在南台灣降下豪雨，荖濃溪支流提供大量的土石進入主流造成淤積，由於布唐布納斯溪持續提供大量土砂，2011年堰塞湖再度形成。為研究此現象本論文以多種野外調查方法記錄荖濃溪地形變化，再以實驗模擬現地情況，實驗內容包含一維及二維實驗，使用一維實驗模擬大範圍的地形變化，二維實驗模擬局部的地貌變化，藉由實驗觀察堰塞湖形成的過程，實驗中許多的現象都可以與現地做比較。研究結果顯示支流土石流對於主流形貌及坡度有明顯的影響。

This thesis uses field survey and laboratory experiments to investigate the relationship between tributary debris flows and tributary dammed lakes at the confluence of trunk rivers with tributaries. Specifically, the focus is on the confluence of the Laonong River with its Putanpunas tributary, where debris-dammed lakes have been observed in 2007 and 2011. During typhoon Morakot, 2009, tributary sediment supply to the Laonong River resulted in aggradation. In 2011, the Putanpunas continued to provide sediment, causing a tributary dammed lake. We used several field survey methods to understand landform variation. In laboratory we used experiment to simulate field situation. Experiment included one-dimensional and two-dimensional. One dimensional experiment simulated large area variation and two dimensional experiment simulated local morphology evolution. In the experiments, we can observe the tributary dammed lake growth process. Many phenomena in the experiments can be compared with field features. The results show that tributary debris flows have a significant influence on trunk river profile and morphology.