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 +/- 700 0m are covered with perennial snow and give rise to a number of valley glac iers all along their southern slopes. The area of study lies just at the fo ot of these mountain ranges and represents a glacial landscape strewn with lakes, morainic ridges and glaciofluvial terraces. The rock types present i n the area are granite gneisses belonging to Thimphu Group. The present stu dy encompasses the geomorphological and geoenvironmental aspects of the are a. This mainly includes processes of formation of dangerous glacial lakes, which cause devastating flash floods on bursting. This glacial belt which f orms the upper catchment of Sankosh (Pho Chu) river has had a history of fl ash floods caused by the bursting of glacial lakes. The latest devastating flash floods took place in 1994, which were caused by the bursting of glaci al lake in the Lunana area. Another glacial lake is in a critical state sin ce a sizeable part of its morainic dam was washed away due to the flash flo ods of 1994. The evolution of this glacial lake and its hydrological, bathy metric and safety aspects are discussed in detail.