Reply on RC2

Abstract

Landslides are one of the natural hazards that are most prominent in tectonically active regions, such as mountainous terrains of the Himalayas. The Himalayan region is vulnerable to landslides due to its fragile lithology, steep slopes, geology, rainfall patterns, and high topographical roughness. Among several factors responsible for slope instability, rainfall is one of the significant drivers that cause a maximum number of landslides. However, very few studies have explored precipitation-induced landslide susceptibility of the Himalayan region due to observational constraints. This study attempts to fill the gaps in the literature by developing a power-law relationship between the maximum rainfall intensity that potentially triggers landslides and the corresponding event duration of selected ‘hotspot’ locations across the Western Himalayan Region (hereafter WHR) that are highly susceptible to landslides. We identified more than 500 landslide events between 2007 and 2016 based on the landslide inventory database, which suggests more than 70 % of landslide events are clustered during the southwest monsoon season. Further, we show an increase in rainfall in recent decades (2007–16) over low elevated areas of the WHR compared to the long-term climatology (1988–2006), revealing intensification of rain events, which could amplify landslide occurrence. Our observational assessment suggests around 28 % of landslides events are followed by within a week of occurrence of triggering rain events. The regionalization of the maximum intensity of triggering rain events versus the corresponding event duration shows that the tail of the triggering rain events tends to follow a power-law relationship with a robust positive exponent of more than one, suggesting synchronicity between two variables. The derived insights would aid in the predictability of shallow-to-deep rain-induced landslide events and inform climate adaptations in steep-slope areas.