集水區上游土石流之發生潛勢主要與（1）河道之坡度、（2）集水區大小、（3）河床堆積情形、以及（4）降雨條件等四參數有密切的關係。本研究針對土石流之地文及水文因子作探討，其中地文因子包括地形與地質因子，地形因子如︰河域坡度、形狀、集水區面積；地質因子如︰河床堆積情形、河床質、流域地質斷層等。水文因子則包括降雨強度、降雨量、雨型、地表逕流及孔隙水壓等相關因子，藉由地文與水文因子對土石流發生潛勢進行評估，就本省已有案例及資料進行歸納分析，並提出土石流潛勢判定模式。 在土石流臨界降雨條件之理論推導部分，本文提出超額孔隙水壓對土石流臨界坡度之影響，並將合理化公式及曼寧公式與超額孔隙水壓之臨界坡度公式相結合，提出土石流臨界降雨強度之理論式。經由現地調查土石流地文因子後，理論公式可以很準確的預測土石流發生之臨界降雨條件，並可供作為土石流避難或預警系統之參考。 就實驗模擬部分，本文針對非凝聚性土石壩在壩趾發生滲流破壞前後之特性作探討。在壩體破壞前，經由理論推導及實驗驗證後，本文所推導之公式可以預測壩體上游面之水位與時間的關係；在壩體發生破壞時，依實驗所得之結果，可用非線性方程式（l'=at'+b*t'^0.5 ）來預測壩體崩壞長度與時間之關係。藉由理論推導與實驗模擬之結果，對因壩體潰流而引發土石流之預警或避難有極大的助益。 The key items related to the occurrence of debris flow are (1)channel slope, (2) drainage area, (3)deposition of sediments on the channel bed, and (4)rainfall condition. The practical method to identify the debris flow prone ravine is explored in this study. A general identification model for the potential de-bris flow ravines, including both the geophysical and the hydro-logical parameters, will be constructed based on the aforementi-oned work. In the theoretical analysis of critical rainfall condition, the effect of the pore pressure on the initiation of debris flow is explored. The experimental data are performed to verify, and are checked with the field data for recorded debris flow events. In the experimental work, the collapse of cohesionless debris dams procedure is explored. By the experimental data and the theoretical formula, the seepage collapse process of the cohesionless debris dams is clearly described in this study. Such information is useful for the warning system of the debris flow.
