ABSTRACT
In Nepal, mountain roads are frequently disrupted by monsoon-triggered landslides and debris flows, posing significant transportation challenges. Given the high costs of slope stabilization and limited protective infrastructure, a rainfall threshold-based early warning system is vital for reducing disaster risks. This study compares the Cumulative Antecedent Rainfall (CAR) and Antecedent Precipitation Index (API) methods using long-term rainfall and landslide data from the mid-Himalayan region. Findings reveal that rainfall is highest in the Lesser Himalaya and decreases toward higher elevations, with July and August as peak months for landslides. The API method, accounting for both short-term rainfall and cumulative soil moisture, identified a 10-day API threshold of 77 mm as a critical trigger. Incorporating such thresholds can enhance preparedness and resilience for vulnerable mountain road networks facing increasing extreme rainfall events.
