反演法於邊坡穩定參數之推導：以蓮華池集水區為例

Landslides and debris flow frequently triggered by heavy rainfall in Taiwan are due to steep terrain, fragile geology, and soil erosions. Under this condition, the analysis composed of hydrological model and the infinite slope model has become a trend in the recent decades. Consequently, previous studies often used static or quasi-dynamic indices as soil moisture in simulation process, or only concerned about un-continuous short-term change of soil moisture variety. Therefore, continuous dynamic simulation has not been commonly implemented. As it is very difficult to obtain detailed and relevant soil cohesion and relative coefficient without on-site measurement or laboratory test, this study took Lien-Hua-Chih Watershed for example, simulated soil moisture varied with rainfall by using Soil Moisture Routing Model, and then calculated dynamic landslides susceptibility with infinite slope model and Monte Carlo simulation. Additionally, we also deduced the minimum root cohesion and soil cohesion of maintaining slope stability by utilizing the character of no landslide within the watershed. Results showed that the proportion of susceptible and non-susceptible cells changed spatially and temporally with effective precipitation and soil moisture. In addition, the factor of safety is strongly influenced by slope, root cohesion and soil cohesion. For example, if the sum of soil cohesion and root cohesion are higher than 10.8 kN/m^2(asuumed soil unit weight= 18 kN/m^3), the 1m depth slope of Lien-Hua-Chih watershed will maintain stable. Such dynamic model-based processes may be used to present the great effects upon landslide susceptibility of rainfall intensity, and help decision-makers choose the most suitable land use.