Anthropogenic infrastructure overrides natural drivers of sediment yield in a major monsoonal river basin

In the regulated river basins worldwide, sediment yield (SY) is essential for water resources management, ecological sustainability, and delta resilience. Yet the controls, from natural to anthropogenic, remain poorly quantified. This study represents a comprehensive analysis of the combined control of natural and anthropogenic factors on the spatial variation of SY in a cratonic monsoonal catchment. We employed Partial Least Squares Regression (PLSR) and multiple linear regression (MLR) to evaluate a set of 36 predictors, including geomorphic, climatic, anthropogenic, land-use, and lithologic drivers, across 19 sub-catchments in the Cauvery basin, India. Although the sample size is small for predictive modeling, the selected sub-catchments effectively capture the basin's heterogeneity. This allowed the PLSR analysis to identify the factors controlling SY. Our results demonstrate that anthropogenic infrastructure is the dominant control. Reservoir area (VIP = 2.45) alone explains 41 % of SY variability, indicating how the construction of dams overrides natural processes. Among natural drivers, rainfall exerts primary control (VIP = 1.77). Catchment scales indicate a strong influence by the high VIP scores for area (VIP = 1.56), perimeter (VIP = 1.59), and stream length (VIP = 1.55). Negative association between SY and scale parameters signifies "dilution effect", where increased sediment storage potential in larger sub-catchments reduces SY. Other geomorphic characteristics, such as localized high curvature and low hypsometric integral (0.22 ± 0.10), are significant but secondary to this scale dependency. The influence of land-use is highly context-dependent. In high-elevation, high-rainfall terrains, the capacity of forest cover to mitigate erosion is counteracted by intense rainfall and steep slopes. We conclude that while geomorphic setting establishes erosion potential, sediment delivery is governed by a hierarchy where anthropogenic infrastructure, rainfall variation, and catchment scale are the principal regulators. Our approach provides a transferable framework for quantifying sediment dynamics in regulated catchments globally, which is essential for sustaining reservoir storage and mitigating ecological impacts of altered sediment regimes.