Assessing river morphological evolution is crucial for sustainable water resource management, particularly in rivers heavily impacted by anthropogenic interventions. This study investigates the Krong No River downstream of the Buon Tua Srah hydropower dam (Vietnam), where riverbed morphology has been significantly modified by reservoir operation and intensive sand mining. The HEC-RAS model was calibrated using field survey data from 2020 to 2023 for both the hydrodynamic and sediment transport modules. A novel finding reveals an approach to quantify the relative contributions of these factors to riverbed morphology. The results indicate that sand mining acts as the dominant driver, as riverbed changes closely match the combined impact scenario, with a small Mean Absolute Error index of only 0.12 m. Meanwhile, reservoir operations exert influence only within a limited area near the dam. Within this zone, if combined with sand mining activities, severe riverbed erosion can occur. Building upon these mechanistic insights, we propose an adaptive management framework that integrates sediment budget analysis and spatially constrained mining zones. This methodology offers a transferable solution for regulated river systems across diverse geographical contexts.
Hang et al. (Mon,) studied this question.