Geoenvironmental Problems of the Glacial Belt of Bhutan Higher Himalaya and Remedial Measures: A Case Study of Raphstreng Lake in Lunana Area

The lofty mountain ranges of Bhutan Higher Himalaya having altitude ± 7000m are covered with perennial snow arid give rise to a number of valley glaciers all along their southern slopes. The area of study lies just at the foot of these mountain ranges and represents a glacial landscape strewn with lakes, morainic ridges and glaciofluvial terraces. The rock types present in the area are granite gneisses belonging to Thimphu Group. The present study encompasses the geomorphological and geoenvironmental aspects of the area. This mainly includes processes of formation of dangerous glacial lakes, which cause devastating flash floods on bursting. This glacial belt which forms the upper catchment of Sankosh (Pho Chu) river has had a history of flash floods caused by the bursting of glacial lakes. The latest devastating flash floods took place in 1994, which were caused by the bursting of glacial lake in the Lunana area. Another glacial lake is in a critical state since a sizeable part of its morainic dam was washed away due to the flash floods of 1994. The evolution of this glacial lake and its hydrological, bathymetric and safety aspects are discussed in detail.