THE STUDY OF WATERSHED TOPOGRAPHY CHARACTERISTICS IN VAKHSH RIVER BASED ON ZY3-DSM

Abstract. The Vakhsh River is one of the major rivers in Tajikistan. The quantitative analysis of watershed topography and developmental characteristics in Vakhsh River catchment can reflect the morphological characteristics of the region, which is of great significance for revealing the quantitative relationship between the hydrological and the geomorphological process. In this paper, the D8 algorithm and the spatial analysis method were used to extract the river networks, the catchment boundary profile lines and the longitudinal valley profile lines of the four major tributaries in the Vakhsh River from the ZY3-DSM of 10 meters resolution. On this basis, five quantitative indices including the frequency of wave, amplitude of wave, gully density, the longitudinal slope and roundness rate were used to analyze the watershed landform and its development degree. According to the experimental results, the catchment have a high surface complexity and a mature landform. Yovonsu river catchment which is in the downstream of Vakhsh River is oval and has low terrain complexity with large frequency and small amplitude. Among the midstream and upstream, the Mukson River has developed into geriatric terrain that is the most mature and has the highest surface complex, while the Obikhingon River and the Kizilsu River have developed into a stable maternal terrain. In terms of topography, the boundary elevation of the Obikhingon is basically in accordance with the normal distribution, while the Kizilsu and the Muksu show a peak state with elevations of 4,000–5,000 m and 5,000–5,500 m, respectively.