劉平妹2006-07-252018-06-282006-07-252018-06-282003http://ntur.lib.ntu.edu.tw//handle/246246/11822We examined aerial photographs taken in 1976, 1980, 1985, 1990 and 1997-2001 to inspect the response of the Gen and Ten-wei-keng rivers (Ninety-nine mountain terrain) upon disastrous typhoons and the 1999 Chi-Chi earthquake, which triggered great landslides and rock falls. A total of 24 transects also was repeatedly surveyed along the Ten-wei-keng river to monitor its evolution since the earthquake. We find: (1) The 2001 Toraji Typhoon resulted in debris flows, the greatest since 1976, in almost all low-order rivers in the study area. Since the typhoon did not bring about particularly severe rainfall, this debris-flow event apparently resulted from the accumulation of debris during the 1999 earthquake, which increased the slope of the rivers. The great supply of debris from the tributaries also caused aggradation in the main valley (ca. 120,000 m 3 debris was deposited in the lower 2 km-long Ten-wei-keng River and its river mouth). Without heavy rainfall, the river became stable within one year after the typhoon, during which minor deposition was only locally detected (downstream of Check-dam VII [1.6 km from the river mouth] of the Ten-wei-keng River and at its river mouth). (2) Construction of Check dams and artificial banks, which stabilizes, steepens river channels and facilitates sediment transport, controlled the evolution of the studied rivers. These constructed river reaches were less widely alluviated during the Toraji Typhoon than during the previous typhoons. The Toraji Typhoon, however, resulted in greater deposition downstream of these river reaches: at the place downstream of Check-dam II (0.9 km from the river mouth) of the Gen River, where erosion dominated during the previous typhoons, and at the mouth of Ten-wei-keng River (creating a debris fan).本研究利用不同年份的航照判識， 及2001-2002 年間野外實測（於田尾坑 溪），嚐試了解九九峰山區自1976 年來 (含1999 年集集地震及2001 年桃芝颱風) 河流形貌及環境的演變。主要結果包括: （1 ）1999 年地震崩落在研究區各支流溪 谷的岩屑在桃芝颱風時經土石流大量向 下游搬運，並造成主流溪谷的加積，規模 為歷年之最。總計約有120,000 立方公尺 的岩屑堆積在田尾坑溪下游兩公里長的 溪谷中。由於桃芝颱風時的降雨在歷年颱 風紀錄中並不算大，也無引發新的山崩， 這大規模的搬運與堆積事件當起因於地 震後支流溪床坡度的增加（因岩屑大量堆 積）。桃芝颱風後至今並未有較大的降 雨，小規模加積僅在田尾坑溪局部河段中 出現（七號攔砂壩下游及溪口），整體河 床並在2002 年秋天以前已趨向穩定。（2 ） 近十年來攔砂壩、河岸護坡的大量興建已 使研究區的河道變窄、整體河床變陡，同 時增加岩屑向下游輸送的效率（田尾坑溪 六號攔砂壩以降，乾溪五號至二號攔砂壩 之間）。即使經歷桃芝颱風，超大量土石 的供應並未能完全淹沒這些整治過的溪 床（不同於整治前颱風時的狀況），這些 土石卻繼續向下輸送，堆積在乾溪二號攔 砂壩下游（先前該河段颱風時一直以下切 為主），並在田尾坑溪溪口造成一土石扇 （並未在其它颱風事件中發現）。application/pdf344917 bytesapplication/pdfzh-TW國立臺灣大學地質科學系暨研究所Debris flowDepositionChi-Chi earthquakeToraji TyphoonCheck Dam土石流河床加積九九峰集集地震桃芝颱風攔沙壩[SDGs]SDG15reporthttp://ntur.lib.ntu.edu.tw/bitstream/246246/11822/1/912116M002033.pdf