Transitioning River System in the Anthropocene: Analyzing Role of Sand Mining on Fluvial Morphology in the Damodar River (West Bengal, India)

Intensive sand mining has emerged as a dominant anthropogenic driver altering the geomorphic stability of alluvial rivers in the Anthropocene. According to the study, sand mining in the Lower Damodar Valley is now a significant geomorphic force that is similar to hydrological variability and significantly alters the shape of channels. Using multi‐temporal satellite imagery (1975–2025), field observations, and reach‐wise geomorphic assessment, the study evaluates two pronounced channel planform metamorphosis of Damodar River – (a) Downstream: transitioning from a relatively stable single‐thread to a progressively unstable and locally braided channel pattern; and (b) Upstream: transitioning from braiding to a deeply incised straight channel pattern. Excessive sand extraction has disrupted sediment–discharge equilibrium, resulting in channel incision, bed degradation, bank erosion, and bar destabilization. In several channel segments, thresholds have been exceeded, producing nonlinear channel responses (quasi‐equilibrium to chaos) in the Anthropocene River. A mining intensity threshold exceeding 1.5 was identified as the critical limit triggering systemic sediment starvation, evidenced by a sharp decline in sediment flux from ~282,000 to ~122,000 tons/year and a cumulative riverbed incision of 16.19 m (mean bed‐level decline: −0.62 m/year), collectively indicating a severe departure from geomorphic steady‐state equilibrium. High Shannon entropy (H > 2.0) in the lower Damodar River indicates highly responsive reaches with unstable sinuosity and braiding, whereas lower entropy reflects constrained channel forms. Grain‐size analysis shows depletion of medium sand (~30%) and increased gravel lag (> 38%), producing bed armoring, elevated Coefficient of Uniformity (C u 13.0–16.0), and low Coefficient of Curvature (C c < 0.5) indicate poorly graded, gap‐graded sediments and disrupted sediment continuity. Chaos analysis reveals nonlinear morphodynamics in flow velocity ( λ = 0.1473) and stronger instability in bed‐level changes ( λ = 0.1570). Positive Lyapunov exponents confirm that localized sand mining amplifies minor disturbances into large‐scale channel instability, complex response, and chaotic geomorphic evolution.