प्रपत्र-5.7-ऊपरी गंगा बेसिन में बादलों के फटने की संभावना एवं संवेदनशीलता का आंकलन

Abstract

In Uttarakhand state, the Upper Ganga Basin (UGB) is frequently witnessing natural disasters like extreme rainfall in the form of cloudbursts, flash floods, which ultimately triggers landslides, and large sediment flow into rivers. The cloudburst phenomena define as sudden heavy deluge of rainfall in a short duration over a very small area 20-30 km2. The cloudburst and its associated disaster is one of the main cause of human causality, livelihood loss, infrastructure collapse, environment issue and migration of the people every year in Upper Ganga Basin. In the present study, reported cloudburst events during the period 2010-2018 were compiled, collated, and geotagged to make an assessment of the spatial and temporal patterns of occurrence, to identify the hotspots susceptible to these events using GIS and remote sensing. Further, the influence of rainfall, land surface temperature, elevation, population susceptible, villages were spatially integrated to analyses the cloudburst events in the UGB.A total of 37 cloudburst events have been reported during 2010-2018. The spatial pattern of occurrence analyzed through plotting 20 km interval profiles. The profiles with very high, high, medium and less vulnerable areas were identified based on the frequency of occurrence of cloudburst events. The blocks viz. Chamoli, Ukhimath, Pokhri, Chinyalisaur, Pabo, Narender Nagar and Bhatwari are most vulnerable from cloudburst events. The correlation between occurrences of event with relief (topography) was analysed. It was seen that majority of the events (about 70%) were reported in elevation zone less than 2000 tn. The spatial rainfall and land surface temperature (LST) w.r.t. occurrence of cloudburst events were also analyzed. Rainfall distribution indicates central and eastern parts of UGB with less rainfall are witnessing higher cloudburst events. The average LST of 20°C to 30°C was common in most of the areas where events were reported. Susceptible villages and population with a buffer zone w.r.t the reported cloudburst event at 2 km, 5 km, and 10 km radius were analyzed. Three buffer rings were drawn surrounding the reported events at a buffer radius of 2 km, 5 km and 10 km proximity. The villages lying under each buffer zones were identified and their corresponding populations noted to measure the number of villages and population likely to be affected due to these events. It was found that about 8 million people spreadover in 3000 villages are prone to cloudburst events with a buffer radius of 10 km from the point of occurrence of reported cloudburst events.