2.3: Fluid-Flow Transport
- Page ID
- 20369
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Fluid flow transport happens when sediment is being carried along with fluids that are responding to gravity. If there is no motion in the fluid then there is no movement of sediment. Sediment can get carried along with these moving fluids in the three main ways described below.
Figure \(\PageIndex{1}\): The main mechanisms of fluid-flow transport include dissolved load, suspended load, and bedload (Figure 13.15 by Steven Earle, CC BY 4.0).
Dissolved Load
The products of chemical weathering result in ions that are dissolved in water. These dissolved materials remain aloft in the water even if it is completely still, the only way to get them out is by a change in concentration and/or biological activity. If the water moves, then dissolved materials are transported along with it.
Suspended Load
Suspended load happens when (usually) silt- and clay-sized particles are held aloft in the water column by the turbulence of flow conditions. Unlike dissolved load, suspended load will settle out if the water stops moving.
Bedload
Bedload transport happens when larger particles (usually sand and gravel) move along with the fluid through some combination of rolling, sliding, creeping, impacts, saltation, eddies, etc.
Video \(\PageIndex{1}\): Bedload sediment transport in an Alaskan stream.
Figure \(\PageIndex{2}\): Sediment-laden waters from the Mississippi River dumping into the Gulf of Mexico. Although all three forms of fluid flow transport are happening in this image, suspended load (the brown plumes) is the most striking (Mississippi River Sediment Plume by NASA Earth Observatory; public domain).