Soil erosion and flood hazard zonation using morphometric and morphotectonic parameters in Upper Alaknanda river basin

In the present study, detailed morphometric, morphotectonic, statistical and hazard analyses have been carried out in the Upper Alaknanda river basin (UAB) located in Central Himalayas, Garhwal, India. The study area is bounded by the South Tibetan Detachment System in the north and by the Main Central Thrust in the south. The major river flowing in the area is Alaknanda which is a major tributary of river Ganga. The purpose of this study is to examine the influence of active tectonics, flood hazard, and soil erosion on the basis of morphotectonic and morphometric parameters using the Cartosat-1 Digital Elevation Model and ArcGIS software. The study area is divided into 10 sub-basins, where 50 morphometric and 6 morphotectonic parameters were calculated. Bifurcation ratio and stream frequency show that streams up to third order is having steep gradient and rolling through highly dichotomized terrain, due to which high overland flow and less groundwater recharge takes places, whereas drainage density clearly indicates the high flood possibility in the region. Morphotectonic parameters indicate relatively young to an early mature geological stage of sub-basins and tectonically active region. The statistical analysis of morphometric parameters is carried out by using correlation analysis, hierarchal cluster analysis, and principal component analysis. Based on their susceptibility to soil erosion, morphometry and landcover classification is carried out to prioritize the sub-basins of UAB. The combined morphometric, morphotectonic and statistical analysis indicates that the area is tectonically active and highly prone to flood, flood induced landslide and soil erosion. The case study of the 2013 flash flood event at three locations Benakuli, JP HEP and Pulna also confirms that the study area is hydro-geologically active to flood and flood induced hazards. The results obtained in this study are directly related to watershed management and hence soil erosion, tectonic activities and flash flood possibilities should be taken into consideration during future development in the area.