Sand mining in the Mekong Delta: Extent and compounded impacts.

Sand mining has accelerated in recent years primarily due to population increase and rapid urbanization. To meet demand, the rate of sand extraction often exceeds the rate of natural replenishment with serious environmental consequences. In this review paper, the Vietnamese Mekong Delta (VMD), a global hotspot for sand mining with a prolonged history of intensive riverbed extraction, is used as a representative case study to highlight the extent and compounded impacts of this activity. The sand mining budget of the VMD ranged from 8.5 to 45.7 Mm/yr. The large difference is due to the use of different methods to determine the sand mining budget as well as the difficulties associated with measuring the volume of sand extracted from the riverbed. Widespread illegal mining in the region further exacerbates the mismatch. The environmental consequences of riverbed sand mining include deeply incised riverbeds that result in riverbank and coastal erosion. Massive sediment removal has also led to river water level reductions, disrupted hydrological connectivity, and diminished floodplain inundation. In addition, the augmented backwater effect that results from riverbed lowering, amplifies the extent of saltwater intrusion in the dry season. While the physical and hydrological impacts of sand mining is well studied, studies on the ecological and socio-economic ramifications remain sparse. In addition, the ways in which upstream dams, irrigation infrastructure, excessive groundwater extraction, and sea-level rise (SLR) have amplified the effects of sand mining was also considered in this review. This paper concludes by advocating for the adoption of remote sensing-based approaches for effective mapping of sand mining activities and the need to mine sustainably to balance developmental needs with environmental conservation.