Hydrogeomorphological characterization of land degradation sensitivity to hydro-climatic variability in the Thamirabarani river Basin, Southern India

Land degradation is a pressing global concern, undermining food security through climate-induced and anthropogenic stresses. This study assesses the hydro-environmental dynamics and land degradation risk in the Thamirabarani River Basin (TRB), southern India using a geospatial approach based on the Land Degradation Vulnerability Index (LDVI). The LDVI was developed by integrating the Climatic Quality Index (CQI), Soil Quality Index (SQI), and Vegetative Quality Index (VQI), derived from multi-temporal datasets, including rainfall records (1980–2023), NDVI, slope, soil type, and topographic wetness, includes climatic variables and aspect-induced microclimatic effects, which influence soil moisture, drainage, and erosion potential relevant to land degradation. The results indicated substantial spatial variability in susceptibility to degradation. Approximately 35.3% of the basin is classified as highly vulnerable (including 5.6% very high and 29.7% high), 24.5% as moderately vulnerable, and 40.2% as minimally vulnerable to land degradation. Rainfall variability, sparse vegetation, and arid conditions further exacerbate worsen land conditions. Subsequent intense monsoonal rainfall generates high surface runoff, leading to sheet erosion, rill formation, and topsoil loss. Multivariate statistical analyses identified slope and aridity as dominant drivers of vulnerability. Principal Component Analysis (PCA) confirmed this, with aridity and rainfall variability showing high loadings of 0.79 and 0.72 on PC2, respectively, while Hierarchical Cluster Analysis (HCA) delineated 25% of the basin as severely degraded, primarily due to anthropogenic pressures. Moderate correlations between LDVI and individual indices (R2 = 0.15–0.18) indicate that land condition deterioration is governed by the interaction of multiple environmental variables. The study emphasizes the necessity for integrated land and water resource management, advocating afforestation, soil conservation, and sustainable agriculture to mitigate ecosystem decline in the river basin.