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SED2D-WES Version 4.3 Beta
τ s = bulk shear strength of the layer.
The bed model. The sink - source term in Equation 1 becomes a source - sink term for the bed model,
d.
which keeps track of the elevation, composition, and character of the bed. Bed change computations utilize the
Crank - Nicholson weighting of the time - step contributions.
Sand beds are considered to consist of a sediment reservoir of finite thickness, below which is a
nonerodible surface. Sediment is added to or removed from the bed at rate determined by the value of the
sink/source term at the previous and present time - steps. The mass rate of exchange with the bed is converted to a
volumetric rate of change by the bed porosity parameter.
Clay beds are treated as a sequence of layers. Each layer has its own characteristics as follows:
a.
Thickness.
b.
Density.
c.
Age.
d.
Bulk shear strength.
e.
Type.
In addition, the layer type specifies a second list of characteristics.
a.
Critical shear stress for erosion.
b.
Erosion rate constant.
c.
Initial and 1 - year densities.
d.
Initial and 1 - year bulk shear strengths.
e.
Consolidation coefficient.
f.
Clay or sand.
New clay deposits form layers up to a specified initial thickness and then increase in density and strength with
increasing overburden pressure and age. Variation with overburden occurs by increasing the layer type value by
one for each additional layer deposited above it. The original version of SED2D-WES and all previous versions of
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WORKING DRAFT
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