LAUSR

The hypsometric integral (HI) is a terrain analysis factor that reflects the landform erosion stage. As a macroscopic parameter, application of HI could reveal the quantitative characteristics of landform evolution at the catchment scale. A 1-arc-second resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer global digital elevation model was used as a basic information source to investigate the spatial variation of HI and the implications for local base levels in the Yanhe River Basin in the Loess Plateau of China. The hypsometric curve was found to be S-shaped, which implies that the Yanhe River is in the mature stage of landscape development. The mean HI value was 0.48, with a maximum of 0.61 and a minimum of 0.14, which indicated that the Yanhe River was in the sub-mature stage. The HI result was compared with longitudinal profiles of the Yanhe River and three local base levels were identified at elevation zones of approximately 1020, 880, and 780 m. The Yanhe River can therefore be defined as being in the sub-mature stage accompanied by intense erosion. This also reflects the erosional signature of the watershed based on the geological stage of development.