Abstract:

As a critical ecological barrier in the middle reaches of the Yangtze River, the Dongting Lake Basin represents a key area for studying the coupling mechanisms between fluvial morphology and geological hazards, such as landslides and debris flows. These interactions constitute an urgent scientific issue in the context of regional ecological conservation and sustainable environmental governance. In this study, we employed a Digital Elevation Model (DEM) to quantify the fractal dimension (D-value) of the river network within the Dongting Lake Basin. A correlation analysis was subsequently conducted between the fractal dimensions and the spatial density of landslide and debris flow events. The results indicate an overall river network fractal dimension of 1.65 across the basin, suggesting a geomorphic system in the mature stage of erosional development. Spatially, the fractal dimensions exhibit a concentric pattern of increasing values. Specifically, the Xiangjiang and Yuanjiang River basins have D-values exceeding 1.70, reflecting complex river network structures with abundant tributaries and high discharge. In contrast, the Zishui and Lishui River basins, along with the areas adjacent to the lake, display D-values between 1.62 and 1.65, indicative of simpler river networks with fewer tributaries and lower discharge. These disparities highlight significant variations in underlying topography, lithology, and hydrological conditions among the sub-basins. Importantly, correlation analysis reveals that higher fractal dimensions are associated with greater river network complexity, which enhances fluvial incision and erosion, thereby increasing susceptibility to geological hazards such as landslides and debris flows.

Key words: Dongting Lake watershed, fractal dimension coefficient, geological hazards, erosion, landslides and debris flows