Sediment Budgets as a Licensing Input for Sustainable River Sand Extraction

Abstract

Sand and gravel are the second most extracted material on earth after water, yet extraction permits are almost universally issued as volume entitlements without reference to how much sediment the river in question actually supplies. This study asks whether the sediment budget — the accounting identity relating sediment inputs, storage and outputs in a river reach — can be operationalised as a licensing input, and what would be required to do so. The method combines a structured review of research published between 2017 and 2024 with a secondary synthesis of published extraction and supply quantities, and a design-oriented analysis that translates the budget identity into licensing parameters. The evidence assembled shows systematic deficit at every scale examined. Global extraction approaches fifty billion tonnes annually and is rising at roughly six per cent per year, while natural production replaces only about half of what is removed. In the lower Mekong, extraction of fifty million tonnes per year confronts a natural sand supply of 6.18 million tonnes, an eightfold deficit associated with bed lowering averaging 0.13 metres per year, and in the Cambodian reach only two of sixty observed months recorded a positive sand budget. The study concludes that volume-based permitting is not a weak form of sediment management but a different exercise, and specifies five parameters — reach definition, supply estimate, deficit tolerance, monitoring interval and an unlicensed-extraction allowance — through which a budget-referenced permit could be constructed with presently available remote-sensing methods.