Environmental Change and Soil Erosion Risk in the Lalmai Hills (Cumilla), Bangladesh: A Secondary-Data Assessment (2005-2025)

The Lalmai Hills in Cumilla are a low-relief hill range with high cultural and ecological value but increasing exposure to land-cover conversion, slope modification, and intense monsoon rainfall. This manuscript provides a secondary-data assessment of environmental change and soil erosion risk over 2005-2025, integrating published studies, open satellite observations, reanalysis rainfall products, and widely used erosion-risk modeling concepts (USLE/RUSLE). We synthesize evidence of declining tree cover, growing built-up footprints, and recurrent hill-cutting pressures, and we map how these changes interact with local topography and rainfall erosivity to elevate erosion risk along disturbed slopes and drainage lines. A conceptual framework and risk pathway matrix are provided to connect drivers, pressures, hazard generation, and downstream impacts on soils, waterways, infrastructure, and livelihoods. Although this is not a full GIS model, the combined evidence indicates a shift toward higher-frequency exposure of bare/compacted surfaces during erosive rainfall, implying increasing sediment yields and localized gully initiation. The paper concludes with a practical monitoring and mitigation agenda focused on slope stabilization, revegetation, runoff control, and enforcement against illegal hill cutting.