...
For physical properties of sediment bed, EFDC+ with the erosion rates option 3 uses below input files to configure the initial model conditions for spatially varying physical properties of sediment bed layers, and these files can be created using sediment core datasets by a sediment bed construction tool in EFDC_Explorer.
sedb.inp: fraction of each sediment class
bedlay.inp: layer thickness
bedbdn.inp: wet density
bedddn.inp: porosity
Note: The erosion rates options 1 and 2 specify the physical properties of sediment bed using SEDFlume datasets. For example, there are only three valid SEDFlume cores (riverine, floodplain, and marine) in this SEDZLJ example model, so the bed properties in the entire model domain are represented by using only those three data sets.
For erosion properties of sediment bed, the erosion rates option 3 employs the same approach as the erosion rates option 2. Specifically, the SEDFlume datasets provide the measurements of erosion rates (cm/s) as a function of applied shear stress (dynes/cm2), and the relationship between erosion rates and shear stress can be defined using Jones and Lick (2001)’s approach as:
where E is erosion rate (cm/s), τb is bed shear stress (N/m2), τcr is critical shear stress (N/m2), and A and n are the fitted parameters based on the SEDFlume core data. With the erosion rates option 3, then, the SEDZLJ algorithm in EFDC+ computes the erosion rates using Equation (1) based on user-defined three erosion rate parameters (A, n, and τcr) and a maximum erosion rate (Emax), which are obtained from the SEDFlume study. The maximum erosion rate is employed for each bed layer in order to prevent the prediction of unrealistically high erosion rates, which might occur due to the exponential formulation of Equation (1) when a high shear stress is applied.
...
Figure 1 Selection of Erosion Rates Option 3: Equation (E = A*Tau^N ) and Bed Properties Using SEDB, BEDLAY, BEDBDN, and BEDDDN - General Tab.
The files sedbfiles sedb.inp, bedlay.inp, bedbdn.inp, and bedddn.inp specify inp specify the initial conditions for sediment bed in the model, and the user can create those files using a sediment bed construction tool in EFDC_Explorer. To assign the sediment bed initial conditions, the user may click Assign Bed IC button in the Erosion Rate Options frame in the General tap (Figure 1), then the Initialization of Sediment Beds window will appear as shown in Figure 2.
...
In Bed Layer Properties and Grain Size Distribution frame, the user may enter the physical properties of each SEDFlume core such as critical shear stress (dynes/cm2), dry bulk density (g/cm3), layer thickness (cm), and grain size fractions (%) for each layer. As discussed above, with the erosion rate option 3, EFDC+ will not use the dry bulk density, layer thickness, and grain size fraction data from the SEDFlume cores entered here (instead, EFDC+ uses the sediment bed properties written in in sedb.inp, bedlay.inp, bedbdn.inp, and bedddn.inp file inp files for model simulation).
In SEDFlume Measured Erosion Rates matrix, the user may enter the erosion properties measured from each SEDFlume core such as Erosion Multiplier (A), Erosion Exponent (N), and Maximum Erosion Rate (cm/s) for each vertical layer.
...