Assessing the multidimensional impacts of riverbed sand mining on geomorphological change and water transfer rate: A comprehensive investigation of Central Vietnam’s Vu Gia Thu Bon River system

Abstract

Increasing populations, urbanization, and infrastructure development worldwide have intensified riverbed sand mining activities, posing complex societal challenges across multiple spheres. Its wide-reaching impacts include alterations of river gradients that intensify erosion, disrupt the flow regime, and influence the stability of fluvial systems. This study aimed to uncover the intricate river dynamics and water transfer rate induced by sand mining in the Vu Gia Thu Bon (VGTB) River basin in central Vietnam. We investigated the effects of sand mining on riverbed elevation, changes in the river morphology, sediment balance, and flow characteristics, including the water transfer rate. The datasets were analyzed using various methods, including theoretical analysis, field investigation, and numerical simulations (TELEMAC-2D). Our findings show that local sand mining activities are unsustainable, affecting riverbed elevation alteration (reduced to 7.45 m), sediment budget (incision by 63.30 Mm³), and morphology over a wide area. We found that sand mining sites on the Vu Gia and Thu Bon Rivers are concentrated mainly upstream and downstream of the Quang Hue Channel, respectively. These factors, combined with the high riverbed elevation slope, led to low riverbed elevation and increased incisions in the Quang Hue Channel, and as a result, increased water transfer rate. We observed that the average annual water transfer rate from the Vu Gia to the Thu Bon via the Quang Hue Channel has increased from 45.7 % in 2018–2022 and is projected to increase further to 65 % by 2030. The result is a change in the rate of water transfer, causing an imbalance in water resources and sediment budgets between the Vu Gia and Thu Bon Rivers. These findings will allow for a more robust understanding of the environmental consequences of sand mining in the VGTB river basin, enhancing the relevance of these findings for policy and management decisions.