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Earth and Space Sciences · Glossary

What is Dissolved load, suspended load, bed load?

Also known as: dissolved load · suspended load · bed load

Definition 20.1 University Earth and Space Sciences — Year 1 · Chapter 20 — Erosion and Transport

The load of a river is the matter it carries past a cross-section, in three parts that differ by how they travel. The dissolved load is the matter in solution, ions and dissolved silica, which moves with the water at its own speed. The suspended load is made of grains held up within the flow by its turbulence, mostly clay, silt and fine sand, which move at nearly the speed of the water and seldom touch the bed. The bed load is made of grains that roll, slide or hop along the bed, in frequent contact with it, much more slowly than the water.

The three loads of a river, seen from the side (schematic, not to scale). The flow is fastest near the surface and slows to zero at the bed. Ions are spread through the whole depth; suspended grains are carried by the eddies, more of them near the bed; bed-load grains roll, slide or make short hops. Right: the forces on a grain of the bed. The drag and lift of the flow tend to roll it over its downstream neighbour, about the contact point; its weight in the water holds it back.
The three loads of a river, seen from the side (schematic, not to scale). The flow is fastest near the surface and slows to zero at the bed. Ions are spread through the whole depth; suspended grains are carried by the eddies, more of them near the bed; bed-load grains roll, slide or make short hops. Right: the forces on a grain of the bed. The drag and lift of the flow tend to roll it over its downstream neighbour, about the contact point; its weight in the water holds it back.
Left: a river in flood carries brown, sediment-laden water (AI illustration). Right: the flood plume of the Mississippi spilling into the Gulf of Mexico around its delta, seen by the MODIS instrument on the Terra satellite on 4 March 2018; the suspended mud colours the sea brown and green, and the southeast wind pushes the plume to the northwest. NASA Earth Observatory image by Joshua Stevens, public domain, via Wikimedia Commons. Left: a river in flood carries brown, sediment-laden water (AI illustration). Right: the flood plume of the Mississippi spilling into the Gulf of Mexico around its delta, seen by the MODIS instrument on the Terra satellite on 4 March 2018; the suspended mud colours the sea brown and green, and the southeast wind pushes the plume to the northwest. NASA Earth Observatory image by Joshua Stevens, public domain, via Wikimedia Commons.
Left: a river in flood carries brown, sediment-laden water (AI illustration). Right: the flood plume of the Mississippi spilling into the Gulf of Mexico around its delta, seen by the MODIS instrument on the Terra satellite on 4 March 2018; the suspended mud colours the sea brown and green, and the southeast wind pushes the plume to the northwest. NASA Earth Observatory image by Joshua Stevens, public domain, via Wikimedia Commons.
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