三義火炎山為一天然土石流坑溝及堆積扇地形，在無人為干擾下，每年均會發生多場土石流，實為台灣觀測礫石型土石流之最佳處所。本計畫擬以三年為期，於三義火炎山一號坑進行礫石型溪溝發生崩塌及土石流之機制分析及現地監測。由現場地文資料收集，並建立火炎山之雨量監測、土石流運動時之地聲、次聲訊號以及影像之多方位監測，整體了解觸發礫石型土石流之降雨條件，及其運動條件及規模與地聲及次聲訊號之關係。本計畫第一年將進行現地之水文與地文資料收集，除收集附近雨量站資料外，本研究設置獨立之雨量站長期監測當地雨量，藉此判定在火炎山當地發生土石流之臨界降雨條件，並利用光達（LIDAR）進行一號坑之地文資料收集，分析山溝、及兩側侵蝕溝之地形特性演變與相應水文條件之關係。第二年著重一號坑地聲及次聲之監測系統，以了解土石流發生過程與降雨特性之關係，並於實驗室進行礫石及塊體不同運動形態與其聲音特性，並以建立土石流運動之聲音觀測門檻值與對應關係。第三年由一號坑影像觀測系統，以量化分析土石流發生規模與降雨特性及河道地文及上游崩塌量之關係。The mechanisms of rainfall-induced landslides and debris flows in Houyenshan gravelly gullies will be explored in this proposed study in a three-year period(2011-2014) , by mainly employing field study and experimental work. The field monitoring system will be implemented on an expanding modular base, which includes the rainfall gauge, geophones and infrasound sensors, ultrasound range-detector and video recording system, respectively. Through the monitoring system, we can first examine the threshold rainfall conditions for landslides and debris flows in gravelly gullies. The acoustic signals in response to the magnitude and flow patterns of gravelly debris flows will be analyzed, which are important information for the warning and evacuation processes for the debris flow prone areas. In the first year (2011/8~2012/7): The analysis of hydrological data and geomorphological data of Houyenshan gravelly gullies: This study collects the available rainfall data and 90/12/21 修訂 2 geographical data of Houyenshan gullies by using 3D Lidar. A rainfall gauge with data logger will be installed in the first Gully of Houyenshan. The threshold rainfall condition for landslides and debris flows will be evaluated consequently. In the second year (2012/8~2013/7): The acoustic signals and monitoring systems of gravelly debris flows: The acoustic and geophone signals will be analyzed. The acoustic characteristics of landslides and debris flows in the gravelly gullies in response to the flow patterns and magnitudes of the debris flows will be evaluated. The significant frequencies related to the granular and liquid content will be further studied with experimental work. In the third year (2013/8~2014/7): The magnitude of debris flows related to the rainfall and geomorlogical conditions of gravelly gullies : we will expand the field monitoring system with the video recording system. Through the PIV techniques and the information provided by the completed monitoring system, the flow velocity and the discharge of the debris flow events related to the rainfall condition, as well as the geomorphology of the gravelly ravines can be obtained. The relationship between the landslides and the debris flows can be further studied with the aforementioned information and the field survey. 研究期間：10008 ~ 10107
