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River bank instability from unsustainable sand mining in the lower Mekong River

Abstract

Recent growth of the construction industry has fuelled the demand for sand, with considerable volumes being extracted from the world’s large rivers. Sediment transport from upstream naturally replenishes sediment stored in river beds, but the absence of sand flux data from large rivers inhibits assessment of the sustainability of ongoing sand mining. Here, we demonstrate that bedload (0.18 ± 0.07 Mt yr−1) is a small (1%) fraction of the total annual sediment load of the lower Mekong River. Even when considering suspended sand (6 ± 2 Mt yr−1), the total sand flux entering the Mekong delta (6.18 ± 2.01 Mt yr−1) is far less than current sand extraction rates (50 Mt yr−1). We show that at these current rates, river bed levels can be lowered sufficiently to induce river bank instability, potentially damaging housing and infrastructure and threatening lives. Our research suggests that on the Mekong and other large rivers subject to excessive sand mining, it is imperative to establish regulatory frameworks that limit extraction rates to levels that permit the establishment of a sustainable balance between the natural supply/storage of sand and the rate at which sand is removed.

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Fig. 1: Sediment dynamics of the Mekong River.
Fig. 2: Bedload transport functions for the Mekong River.
Fig. 3: Morphological impacts of sand mining on river bathymetry.
Fig. 4: The impact of channel bed lowering on river bank stability.

Data availability

The raw bedload transport data collected with the multibeam echo sounder, the discharge and suspended sediment data generated from the ADCP, and bank profiles collected with the terrestrial laser scanner that support the findings of this study are available from the corresponding author upon reasonable request. The water discharge data used to generate the bedload ratings curves are from the hydrological records archived in the Mekong River Commission data portal (http://portal.mrcmekong.org/index; discharge records from Kratie (station identifier 014901; unique dataset accession 2811)).

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Acknowledgements

This study was supported by awards NE/JO21970/1, NE/JO21571/1 and NE/JO21881/1 from the UK Natural Environment Research Council (NERC). We thank the Mekong River Commission for access to hydrological and suspended sediment data, and the Department of Hydrology and River Works in Cambodia for logistical support and help in the field. J.L.B. was in receipt of a University of Southampton Diamond Jubilee International Visiting Fellowship that aided the completion of this work.

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C.R.H., S.E.D., D.R.P., J.L., J.L.B., A.P.N. and R.A. jointly conceived the study. C.R.H., S.E.D., J.L., J.L.B., D.R.P., R.A. and R.C.H. collected and processed the field data. C.R.H. constructed the bedload transport functions and undertook the data analysis. C.R.H and S.E.D. undertook the bank stability analysis. C.R.H. drafted the paper, which was then edited by all co-authors.

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Correspondence to Christopher R. Hackney.

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Hackney, C.R., Darby, S.E., Parsons, D.R. et al. River bank instability from unsustainable sand mining in the lower Mekong River. Nat Sustain 3, 217–225 (2020). https://doi.org/10.1038/s41893-019-0455-3

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