Real-time drought and landslide monitoring in the Trishuli catchment, Nepal
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Its high-relief topology, active seismic zone, and intense summer monsoons make Nepal very prone to the occurrence of multiple hazards, among which droughts and landslides (MoHa, 2019). The impact of droughts on the food security and economic development in Nepal is considerable since 65% of the households relies on rain-fed farming (FAO, 2020). Also, landslides have a large impact on the liveability in Nepal, causing considerable economic losses and fatalities every year (Petley et al., 2007); in 2017 and 2018 a total of 484 landslides were reported in Nepal, leading to 161 casualties and an economic damage of 1.6 million USD (MoHa, 2019). To improve drought and landslide risk awareness and preparedness, real-time monitoring of these hazards is necessary. Although many systems monitoring these hazards have been developed and implemented, these systems or their applications often only provide hydrometeorological information displayed on low spatial resolution. There is, however, a need for information that is comprehensible, directly applicable, and, therefore, helpful to drought and landslide risk awareness and early warning on local scale. Therefore, this study has investigated methodologies and visual output for a multi-hazard monitoring model that provides accessible information on agricultural drought occurrence and rainfall-triggered landslide potential in the Trishuli river basin of Central Nepal. These methodologies use meteorological variables at point scale obtained from ECMWF’s ERA5 product that is downscaled with meteorological station measurements at different locations throughout the catchment area. For the monitoring of drought impact on rice, wheat, and maize production a visualisation is developed, indicating crop seasonal water availability based on the estimation of Makkink evapotranspiration and a subsequent climatic water balance. Landslide risk has been estimated by comparing the daily index of antecedent rainfall (ARI) to a threshold of extreme antecedent conditions. Although inaccuracies exist for these methods in establishing drought and landslide extent or potential, all methodologies are easy to implement and provide comprehensible insights on landslide or drought occurrence on station scale. Therefore, it is suggested to apply the developed methodologies to real-time or forecasting meteorological measurements to provide real-time monitoring and early warning of landslide and drought occurrence in Central Nepal.