IMPROVING SLOPE STABILITY AND MITIGATING LANDSLIDE RISK IN THE MAJES IRRIGATION PROJECT, PERU

We investigate the underlying mechanisms causing slope instability and landslides that are impacted by flood irrigation in the Siguas River Valley of the Majes Irrigation Project region in Peru. We examined the hypothesis that the development of a perched water table, impacted by overlying flood irrigation practices, leads to significant slope instability within the region. Using numerical modeling to analyze subsurface flow dynamics, our results corroborate that developing a perched water table beneath the agricultural area directly impacts landslide risk. We then adjusted the models to account for improving the topsoil’s hydraulic conductivity to varying values to simulate various biochar amendment application possibilities. Results show that an improvement in soil hydraulic characteristics would increase the time to failure for nearby slopes by up to 2 years for biochar applications alone. Investigations were also carried out to consider further improvement if both biochar application and reduction in irrigation volume were applied simultaneously. Results showed the most significant improvement in time-to-failure results of about 5.7 years, occurred with an improvement in hydraulic conductivity of 12% along with a reduction in irrigation volume by 25%.