Extreme weather event-driven evolution of mass movements over upper, middle, and paraglacial zones of a Central Himalayan catchment

Extreme weather events, i.e., heavy rainfall, trigger widespread mass movements, producing large volumes of unconsolidated sediments that continue to shape geomorphic processes long after the event. However, the post-event evolution of precipitation-triggered landslides remains much less known, especially in paraglacial mountain systems. This study examines the decadal evolution of landslides in the Mandakini catchment, Uttarakhand, India, a landscape characterised by three distinct geomorphological zones: the lower fluvial, middle paraglacial, and upper glaciated regions. Using multi-temporal LISS-IV and PlanetScope imagery (2014–2023), the characteristics and activity of landslides were assessed across these zones. Results show that landslide activity peaked immediately after the 2013 Kedarnath disaster and declined gradually, although there was an increase in activity in 2018, 2020, and 2023, with clear geomorphic controls. The fluvial zone exhibited the highest landslide densities and continued reactivation, whereas the paraglacial zones were largely characterised by debris flow-type landslides that remained largely dormant, except for renewed movement in 2023. High-intensity short-duration rainfall emerged as a major trigger regardless of antecedent moisture, driving a marked surge in new landslides and debris flows during the 2023 monsoon. Additionally, anomalously high winter precipitation coincided with elevated debris-flow activity in the paraglacial zone, suggesting a significant role for snowmelt, which is likely to intensify under rising temperatures. Roughly 40% of the landslide-impacted area was fully revegetated by 2023. These findings highlight how a paraglacial terrain, rainfall extremes, and evolving snowmelt patterns collectively shape long-term slope sensitivity, with implications for hazard assessment and targeted mitigation in the Himalayas and similar environments worldwide.