Publication

Sediment flushing downstream dams: a study on the clogging by fine sediments

Abstract

Water reservoirs used to produce electricity have an impact on the environment and durability by : • stopping the natural sediment flux • changing the flow regime downstream of the reservoirs • storing (fine) sediments that reduce the storage volume Those 3 issues have been leading to the development of strategies in order to improve the equilibrium of the ecosystem downstream such structures, with solution such as sediment flushing and simple water flushing reproducing flood events. Those operations produce excessive sediment inflow on certain river sections, which can lead to the clogging of the gravel bed. River construction work, soil erosion, emergency actions and natural river bank erosion can also bring similar problematic. For example, a dramatic event happened in 2013 on the Spöl River in Eastern Switzerland. Due to some operations on a Punt dal Gall dam, important amountsof fine sediments were flushed downstream the reservoir and resulted in significant damages to the river ecosystem1. A strong clogging of the river bed was noted. A clean water flushing a few months later led to a cleaning of the clogged areas.

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Related concepts (34)
Sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation; if buried, they may eventually become sandstone and siltstone (sedimentary rocks) through lithification.
Sediment transport
Sediment transport is the movement of solid particles (sediment), typically due to a combination of gravity acting on the sediment, and the movement of the fluid in which the sediment is entrained. Sediment transport occurs in natural systems where the particles are clastic rocks (sand, gravel, boulders, etc.), mud, or clay; the fluid is air, water, or ice; and the force of gravity acts to move the particles along the sloping surface on which they are resting.
Marine sediment
Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor. These particles have their origins in soil and rocks and have been transported from the land to the sea, mainly by rivers but also by dust carried by wind and by the flow of glaciers into the sea. Additional deposits come from marine organisms and chemical precipitation in seawater, as well as from underwater volcanoes and meteorite debris.
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