This paper quantifies the magnitudes of mass-wasting caused by the Asia Summer Monsoon, extreme rainfall, and earthquakes in the Nepal Himalaya. In mountainous environments, quantifying the drivers of mass-wasting is fundamental for understanding landscape evolution and improving hazard management. Using a newly compiled 30-year mass-wasting inventory, the researchers establish empirical relationships between monsoon-triggered mass-wasting and monsoon precipitation, before quantifying how other mass-wasting drivers perturb this relationship.
This paper finds that: (1) extreme, 5–30-year return period rainfall events can induce mass-wasting perturbations. (2) The 2015 perturbation is controlled by short-term Gorkha earthquake-induced landscape preconditioning. (3) The signature of landscape preconditioning is controlled by the coincidence of peak ground acceleration (PGA) and excess topography. (4) Earlier large magnitude earthquakes in 1934, 1988 and 2011 did not compound the 2015 preconditioning, suggesting that longer-term preconditioning damage was not a major driver of landsliding here.