Sand is a valuable and increasingly rare raw material: it is the main component of concrete, glass is made of sand, and it is much in demand both in construction and in the industry. In a recent report issued in May 2019, the UN environment programme described sand as a valuable raw material for various industries - such as construction or land reclamation - and the second largest resource traded by volume after water (see: https://unepgrid.ch/en/resource/2AD54)533). In view of this, the market for sand as a raw material has become highly competitive, resulting in increasing informal sand excavation from riverbeds. Unsustainable sand mining has severe consequences such as bank or coastal erosion, which affect both the environment and humanity.
Over the past years, a research project of Ludwig Franzius Institute of Hydraulic, Estuarine and Coastal Engineering (LuFI), which is based at Leibniz University Hannover, recorded the sand deposit and transport capacity in the delta of the Mekong River in Vietnam. Based on extensive measurements, researchers were able to draw detailed conclusions on local informal sand mining activities and the unsustainable development of the sand budget. The findings of the sub-project in collaboration with Helmholtz Centre Potsdam German Research Centre for Geosciences (GFZ) and Vietnam National University (VNU) have now been published in the renowned journal "Scientific Reports" (see www.nature.com/articles/s41598-019-53804-z). "Scientific Reports" is a scientific journal published online by the Nature Publishing Group.
Within the scope of the Catch-Mekong project, which is in receipt of funding from the Federal Ministry of Education and Research (BMBF), researchers collected high-resolution hydro-, morpho- and sedimentological data in the Mekong Delta. In the course of two extensive measurement campaigns during the dry and wet season in 2018, researchers assessed depth data using a multibeam echosounder in order to determine flow velocities and sediment transport. "Since the Mekong Delta is already shaped by progressing bank erosion in urban areas, our scientific investigations focused on determining the inventory as well as the seasonal budgeting of the sand deposit and transport capacity", said Prof. Dr.-Ing. Torsten Schlurmann head of the sub-project at LuFI.
"Within the framework of our study, we were able to draw detailed conclusions on local sand excavations, which exceeded the amount determined in the licences awarded for sand mining. The processed data indicated that local dredging activities were significantly increased over the past years", asserted Christian Jordan, a member of research staff and doctoral candidate at LuFI.
According to the international team of researchers, new sediment supplies originating from the middle and upper reaches of the river are already insufficient for compensating the extracted sand in the delta. The sand deficit results in increased bank and coastal erosion, which could cause landslides, inflow of salt water, and soil salinity - with severe consequences for the lives and livelihood of approximately 18 million residents in the delta. "In the context of the increased use of water power in the Mekong area and the construction of more than a dozen new dams, the stability dilemma gets even worse in the lower reach and the delta of the Mekong due to additional sediments remaining in the middle and upper reaches", said Dr.-Ing. Jan Visscher, chief engineer and head of measuring campaigns for the Mekong Delta project.
The Mekong Delta - also known as the ''rice bowl'' of Vietnam - yields over 50 percent of the country''s food supply. The wet and flat terrain provides ideal conditions for cultivating rice. For the first time, researchers were able to demonstrate that this habitat is highly endangered due to informal and unsustainable sand mining and the resulting destabilisation of the river.
Note to editors:
For further information, please contact Prof. Dr.-Ing. Torsten Schlurmann, Ludwig Franzius Institute of Hydraulic, Estuarine and Coastal Engineering, LuFI (Tel +49 511 762 19021, Email schlurmann@lufi.uni-hannover.de or Christian Jordan, also LuFI (Tel +49 511 762 2788, Email jordan@lufi.uni-hannover.de).
