The impacts of excessive sand extraction in the Mekong Delta have been documented in many reports, driven primarily by the burgeoning sand demand in the high-growth national and regional construction sector. The reducing availability of sediments is exacerbated by the building of hydroelectric dams, and may also be worsened by the impacts of climate change. There is a resulting significant loss to fishing and rice cultivation in the Delta region, compounded with riverbank erosion and saltwater intrusion. The latest estimates indicate a threefold reduction in sediment transport over the last three decades, and a similar reduction in the sand component to possibly only 3-5mt/year now. Thus the over-extraction of sand requires urgent remedial measures.
The demand of aggregates in Viet Nam is estimated at about 4 tons/capita, which translates to 400mt/year nationally, of which 100mt/year of aggregates are used in the combined VMD and HCMC region, with its population of 27m people. While the sand component of this might be 30mt/year, the indications are that total sand demand significantly outstrips river supply, though there may be unquantified supplies also from non-river sources. This again implies measures to better regulate river sand extraction within sedimentation budget, and to develop supplies of alternatives such as manufactured sand and recycled and other waste materials.
The successes and failures of legislation and regulation concerning river extraction in twelve countries, namely China, India, Malaysia, Colombia, Mexico, USA, Canada, New Zealand, UK, Netherlands, Myanmar and Japan, predominantly based on experiences of GAIN members. In each case, best practices and pitfalls are identified. This section also assesses for each case study the wider issues of permitting procedures, sedimentation estimation, technical best practice operating guidelines, including compliance monitoring and associated penalties. Some case studies (such as Mexico and Myanmar) admit lack of success that is mainly because of not meeting the requirements of the four elements: legislation and regulation, permission for river sand extraction and compliance monitoring. In addition, economic drivers and the needs of infrastructure development impact on the effectiveness of enforcement and enactment of legislation and regulation. Particularly, in Mexico, the illegally extracted sand and gravel are exported and sold to US construction companies at vast profits; in Myanmar, a construction boom has fueled a sharp increase in the extraction of sand. Case studies in India and Malaysia have just been partially successful. However, India has implemented the strategy that replacing natural sand by manufactured sands (“M-sand”), produced through crushing quarry fines, is being now adopted in other states. This program can be considered as a good practice to reduce pressure on river sand demand. In some countries like Canada, the UK and the Netherlands, river sand extraction only allowed to facilitate flood control, enhance river flow and river navigability. Besides, river dredging activities are regulated specific exploited areas and rigorous monitored. In developed countries (specific cases such as USA, New Zealand and Japan) river sand mining has been virtually eliminated, supply instead being from hard-rock quarries.