Hillslope Stability in the Yellow River Source Zone

Tectonic uplift is the primary control upon the low relief yet moderately undulating plateau landscapes that make up much of the source zone of the Yellow River. Steep ravines and gullies are restricted to mountain ranges at the northern and southern margins. This contrasts starkly with the deeply dissected landscapes at the eastern margin of the Qinghai–Tibet Plateau. Although the high elevation induces low mean annual temperatures, diurnal temperature ranges are high. Precipitation is sparse but concentrated, and gales are frequent. Hillslope processes such as landslides, debris flows, solifluction and soil erosion are extensively developed in the region. This chapter presents an overview of hillslope stability in the Yellow River Source Zone. First, the landscapes and topography of the Yellow River Source Zone are introduced. Landslide, debris flow, soil erosion (aeolian and rill/gully) and freeze-thaw processes are shown to be key drivers of patterns and rates of grassland degradation. Human activities and climate change are key agents of landscape change. The influence of vegetation management upon hillslope stability and in reducing geological disasters is demonstrated. Vegetation plantation and increased vegetation cover enhance the mechanical and hydrologic effects of hillslope protection, increasing soil shear strength and interception of rainfall.