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Bed load sediment in the thalweg of Campbell Creek in Alaska. The term bed load or bedload describes particles in a flowing fluid (usually water) that are transported along the stream bed. Bed load is complementary to suspended load and wash load. Bed load moves by rolling, sliding, and/or saltating (hopping).
Direct and indirect methods are two ways in which bed material can be measured. Direct measurement is done through the use of a physical trap, placing the device in contact with the bed, “allowing the sediment transported as bedload to accumulate (or be trapped) inside the sampler for a certain amount of time, after which the sampler is raised to the surface and the material is emptied and ...
Bed load rolls slowly along the floor of the stream. These include the largest and heaviest materials in the stream, ranging from sand and gravel to cobbles and boulders. There are two main ways to transport bed load: traction and saltation. Traction describes the “scooting and rolling” of particles along the bed (Ritter, 2006).
Bed load transport rates may also be given by a ratio of bed shear stress to critical shear stress, which is equivalent in both the dimensional and nondimensional cases. This ratio is called the "transport stage" ( T s or ϕ ) {\displaystyle (T_{s}{\text{ or }}\phi )} and is an important in that it shows bed shear stress as a multiple of the ...
The boundary between bed load and suspended load is not straightforward because whether a particle is in suspension or not depends on the flow velocity – it is easy to imagine a particle moving between bed load, part-suspension and full suspension in a fluid with variable flow. Suspended load generally consists of fine sand, silt and clay ...
The composition of the wash load changes as the bed load changes. According to Einstein, all particles that are not significantly represented in the deposits of the bed "must be" considered wash load. This means that as the bed load moves down the river and the size of the bed load is reduced so is the size of the wash load.
The concentration of suspended sediment with depth goes as the power of the negative Rouse number. It also is used to determine how the particles will move in the fluid. The required Rouse numbers for transport as bed load, suspended load, and wash load, are given below.
The capacity of a stream or river is the total amount of sediment a stream is able to transport.This measurement usually corresponds to the stream power and the width-integrated bed shear stress across section along a stream profile.