Integrated numerical modeling of landslide-induced wave at Shahrchay Dam using PLAXIS and MIKE 21

Abstract

Landslides entering dam reservoirs can generate hazardous impulse waves that threaten human lives and infrastructure, particularly in densely populated downstream areas. The Shahrchay Dam, located 12 km upstream of Urmia city (population > 700,000), is situated near an unstable slope within its reservoir, raising significant concerns for dam safety. This study employed a sequential geotechnical–hydrodynamic modeling framework: PLAXIS was used for slope stability analysis and landslide volume estimation, and MIKE 21 was subsequently applied to simulate wave propagation. Key parameters investigated included landslide velocity, reservoir water level, and landslide volume. PLAXIS analyses yielded a safety factor of 1.05 for the critical slope, indicating high susceptibility to sliding, while MIKE 21 effectively simulated the resulting wave dynamics. Results showed that increasing landslide velocity from 7 m/s to 13 m/s increased wave height at the dam crest by 33%. Raising the reservoir from the minimum level (1,566 m) to the 10,000-year flood level (1,585 m) resulted in a 46% increase in wave height. Additionally, doubling the landslide volume (from 840,000 to 1,764,000 m3) led to a 48% increase in wave height at the dam crest.