Evolution of the Yigong river channel on the Eastern edge of the Qinghai-Tibet Plateau: insights from hydrodynamic geological hazards shaping topography

Abstract

Geological action is one of the main forces in the formation of topography, especially in the southeastern part of the Qinghai-Tibet Plateau. Collapse, landslide, mud-rock flow and other geological actions are the main factors affecting the evolution of river valley landforms. However, existing inference methods primarily rely on theoretical calculations and multi-temporal remote sensing image interpretation, lacking direct analysis and validation through geological exploration techniques. In response, this study employed geological engineering and geotechnical exploration techniques to investigate the impact of debris flows, landslides, and collapses on the evolution of topography and geomorphology in a 5.0 km section of the Yigong Zangbo Basin. Through drilling and geophysical exploration, 6 geological profiles were constructed, identifying the distribution range and development characteristics of the geological phenomena within this section of the river valley, revealing the distribution positions of both the new and old river channels, and inferring the evolution of the river bedrock based on the original topography. The study found that when geological phenomena occur, substantial material is transported into the river channel, altering its original shape and influencing the river’s erosion process. Additionally, the occurrence of geological phenomena is closely correlated with the evolution of river valley morphology. When the river valley is wide, material accumulation on one side causes the river to flow along a lower position on the opposite side, primarily resulting in the river’s bending on the plane. In contrast, in narrow river valleys, material accumulation on the sides can fill the entire river channel, leading to a rise in the riverbed. These research findings provide a critical theoretical basis for understanding river valley morphological evolution and informing basin engineering construction.