An analysis of geomorphologic characteristics of the Yellow River source region based on ASTER-GDEM

Abstract：Based on ASTER-GDEM (30m) data and geological information and adopting color-dye, density-class and GIS spatial analysis technology, the authors studied geomorphologic characteristics of theYellow River source region by means of topography-elevation analysis, surficial-slope analysis, terrain-section analysis and hypsometric analysis. According to the research results, the Yellow River source region is a NW-SE-trending ribbon basin with an average elevation of 4473m, an average surface rolling of 60m and an average slope of 9.5°, thus belonging to the high-altitude basin. The basin is flat with steep edges. In the basin there are lots of lacustrine strata 4200~4300m in altitude, characterized by slight undulation. The internal basin was once a fossil lake bed and then turned into what it is by fluviation. There are three layered geomorphic surfaces inside the basin 4400m, 4500m and 4600m in attitude respectively, which constituted large-size fluvial terraces due to the influence of the fossil lake. There are mountains on the edges of the basin with steep ravines, formed by mountain uplift and drastic tectonic activity as well as strong weathering action. The geomorphologic characteristics of the Yellow River source region were strongly affected by tectonization: Kunlun fracture, Buqingshan piedmont fault, and Bayan Har Mountain piedmont fault on the edges of the basin exerted a controlling influence on the layout and the entire geomorphologic characteristics; Madoi fault，Bayan River fault and Maduo-Buffalo ditch fault within the basin broke the stratified relief of the lacustrine terraces, and played a main role in forming the terrain and the overall layout of the Yellow River source region water system. The region integrally is at its maturity stage and is the comprehensive result of tectonic activity and fluviation action. The largest drainage area is located in the region with the altitude from 4200 to 4800m, occupying 90.6% of the total region. It is a flat terrain formed by long-term internal flow function, which is considered to be the result of fossil lake fluviation. The piedmont area on the northern and southern side of the basin experienced strong tectonic actions with obvious weathering, which is now at its old-age stage. The river valley geomorphology in the southeast of the basin is at the youth stage. Estimated from its terrain characteristics, the Yellow source water system is relatively young.