Impact of reservoir impoundment-caused groundwater level changes on regional slope stability: a case study in the Loess Plateau of Western China

Due to its impact on regional groundwater levels, the impoundment of a reservoir is an important consideration for assessing the stability of surrounding slopes. This study presents a method for risk assessment and control of landslides in regions where groundwater levels can be affected by reservoir water levels. The method is illustrated with a case study of the Hongzhuang reservoir in Yanan city, northern Shaanxi province, China. A groundwater numerical model was developed using MODFLOW and the groundwater flow fields were calculated for different reservoir water levels. Safety factors were then obtained and the slope stability was analyzed. Moreover, a probabilistic slope analysis was performed by Monte-Carlo simulation to evaluate the reliability of slope stability and the probability of slope failure. Finally, a reasonable reservoir water level was determined according to the acceptable risk level, and a comprehensive risk mitigation method was proposed considering water level control, relocation, and drainage measures.