Sediment generation potential of permafrost in two neighbouring Himalayan river basins: a first order geomorphic analysis using GIS

The permafrost component of the Himalayan cryosphere has received comparatively lesser attention than the glacier and snow component. But permafrost response to increased temperature will be no less significant.With the rise of temperature, permafrost disintegration apart from its hazard dimension, will increase mass wasting processes and will change sediment flux in a major way in permafrost bound Himalayan rivers. This can have major impacts on downstream fluvial forms and processes. A first order geomorphic analysis of the Permafrost Zonation Index (PZI) data is carried out with topographic parameters like elevation, slope, aspect and excess topography. The analysis shows variable sediment yield potential over space and time in two neighbouring Himalayan river basins viz., the Sutlej and Yamuna river basins. These two river basins have varying permafrost cover. The larger permafrost area, dominance of northerly aspect, lower slope of the permafrost region and distribution of excess topography over a wider range of elevation especially in the higher elevation belt in the Sutlej River basin mean that disintegration of permafrost will result in more sediment yield and will occur over a longer time frame as compared to the Yamuna River basin. More sediment yield will translate into aggradational processes in downstream.