| Erosion & sedimention control
Left: Union of two rivers with high and low sediment content in India Photo: Bodo Bookhagen
High mountain rivers
Many high-mountain rivers in Asia transport more sediment downstream compared to a few years ago, with such changes in sediment levels having a particularly strong impact on agriculture, water quality, flood management, and hydropower generation. A study undertaken by the University of Potsdam in Germany has demonstrated the interacting roles of glaciers, vegetation, precipitation, and slope in mobilising sediment and controlling the current sediment transport in rivers. “The specific sediment yield in catchments with
high glacial cover is on average an order of magnitude higher than glacier-free basins, and appears overall higher in Asia’s glacierised catchments than those reported for the European Alps, the Andes, or Norway,” said Bodo Bookhagen, Professor for Geological Remote Sensing at the University of Potsdam. He goes on to explain that the fluvial suspended sediment threatens the water quality downstream and thus the aquatic ecosystems, the river infrastructure such as hydropower plants and bridges as well as agriculture and pastoralism. The team investigated 151 rivers around the Tibetan
plateau and demonstrated that glaciers exert a first- order control on fluvial sediment yield, especially with high precipitation and in high glacier-cover basins. “Our work highlights the many competing factors in
controlling the transported material in river catchments and shows that a more accurate prediction of the sediment volume should consider not only climate change, but also glacier dynamics and vegetation changes and their interactions with slope,” Bodo Bookhagen emphasised. Vegetation influences sediment transport especially in the Eastern Tibetan Plateau and Tien Shan. Depending on climate zone, vegetation can either promote erosion of material or have a stabilising effect on slopes. These findings call for a systematic basin- wide approach to climate change adaptation in high mountain regions.
www.waterpowermagazine.com | April 2025 | 33
Interception A joint research pilot project between the US
Army Corps of Engineers, the US Army Engineer Research and Development Centre (ERDC), and the Missouri Sedimentation Action Coalition was recently conducted on the Niobrara River in northeast Nebraska. Its aim was to test new technology designed to intercept sediment from the riverbed before it reaches Lewis and Clark Lake. More than 50% of sediment deposited into the Missouri River reach that makes up the Lewis and Clark Lake delta comes from the Niobrara River. The spring-fed river travels along the northern edge of the Sand Hills of Nebraska and produces a nearly endless supply of sediment through bank, gully, riverbed, and overland erosion. As a result, the water surface elevation of the Missouri River throughout the Lewis and Clark Lake delta has continued to rise since the lake was formed in 1955 causing increased flood risk, higher ground water levels and water quality and supply issues for nearby communities.
Engineers participating in the project tested a 3.6m bedload sediment collector to determine how much sediment could be captured from the Niobrara River before it reaches the delta.
Below: The West Rapti River in Nepal is described as being dynamic with the capacity to carry a large sediment load
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