Downie Slide: numerical simulation of groundwater fluctuations influencing the behaviour of a massive landslide

Groundwater levels at Downie Slide have varied during the development of and over the operating life of the Revelstoke Reservoir. Drainage system construction successfully lowered groundwater levels through the central portion of the slope; reservoir filling resulted in water table rise near the inundated toe, and over the operating life of the hydro-electric facility gradual, minor losses to the drainage system capacity have resulted in a slow rise in water table levels. Calibrated models capable of reproducing observed deformation patterns at Downie Slide have been tested with changing groundwater levels. Models perform well, adequately reproducing observations of global slope response to changes in piezometric boundary conditions. These models have also been used to test potential trigger scenarios, including rapid reservoir drawdown and a total loss of drainage system capacity.