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Sedimentologic Engineering in Grand Canyon
Some previous studies had suggested that most sand introduced by tributaries remains in storage in the channel. If this were the case, resource managers could wait for several years to allow tributary sediment to accumulate in the main channel before scheduling an artificial flood to rejuvenate the river habitat by redistributing the sediment. Results of this CMG-WRD project indicate that most tributary sediment does not remain in storage for years, but instead is transported out of the canyon relatively quickly. To have the maximum amount of sediment available, it is necessary to schedule habitat-enhancing floods shortly after tributary-influx floods.
The lens of the video camera rests on the sediment bed, protected by a thin layer of clear plastic. Because the camera views through less than a millimeter of water, the system can function in water with extremely high turbidity. The camera includes a LED (light-emitting diode) light source, is very small, and can be deployed rapidly and easily. Images from the camera will be processed digitally to determine grain size. Additional work was performed with a suspended-sediment-sampling device. The sampler is lowered to the bed, and a solenoid opens a calibrated sampling nozzle. While the sampler is raised to the surface, it samples water and sediment at each depth in proportion to the speed of the water flowing at that depth. The samples obtained by this procedure contain depth-integrated sediment and water (in the same proportion in which they are transported downstream). By knowing the water discharge, the sediment-transport rate can be calculated.
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![]() in this issue:
Grand Canyon Sediments
Earth Science Week in Woods Hole ![]() |