Quantitative Terrain Analysis of the Great Canyon Region of Yalungzangbo River,Tibet and Discussion of Its Origin

In this paper,we take new SRTM-DEM data for digital elevation analysis,field surveying and chronology of sediments as means to study topographic features and its origin in the great canyon region of Yalung Zangbo River in Tibet.The new SRTM-DEM data are used for quantitative analysis for terrain.The overall geomorphic features are the high-altitude,high-relief and flat peaks(North).ArcGIS software,an analysis platform,is used to obtain statistics for Maximum-Mean-Minimum elevation profiles from a strip area in its SRTM-DEM.These profiles show that the change of Mean elevation is controlled by the change of Maximum elevation.Incision depth of different geological units can be calculated by Max and Min elevation profiles.Sediments in valleys include moraines and icy lake sediments formatted after late Pleistocene which is confirmed by our field investigation and chronological data of sediments.To sum up,glacier,drainage network incision and outflow drainage system control the geomorphology in the great canyon region of Yalungzangbo River during the cause of terrain formation.The Glacier on the high mountain is an important external factor that controls 'unroofing'.Drainage network incision and erosion play an important role of relief terrain.Due to the fact that basin filling is limited by outflow drainage system,not only deposits in moraines but also icy lake sediments in valleys are younger.