Erosion Rates Option 1

Users may select Lookup Table and Bed Properties as Core ID for the erosion rates option in the General tab (Figure 1) if SEDFlume datasets provide the measurements of erosion rates (cm/s) as a function of applied shear stress (dynes/cm²) for each layer of a SEDFlume core.  For using this option, the user would need to manually define lookup tables of erosion rates versus bed shear stress based on the measurements from the SEDFlume analysis, EFDC+ then will determine the erosion rates of sediment bed according to the lookup tables given the modeled bed shear stress during the simulation. 

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The Lookup Table and Bed Properties as Core ID option requires the Number of Shear Stress Categories to Calculate Erosion Rates in the Sediment Bed tap (Figure 2), and the user needs to enter the number of the shear stress classes that were applied when measuring the erosion rates in the SEDFlume core tests.

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After specifying the number of shear stress classes, the users need to complete the Core Definitions tab (Figure 3) using the SEDFlume core datasets (prior to the Erosion Rates tab), which would be used for defining the physical and erosion properties of parent-bed layers in a model.

The user may enter the Number of SEDFlume Cores and then assign the measurements for physical and erosion properties associated with each core. For example, if the SEDFlume data consists of the measurements for three sediment cores, the user can set the Number of SEDFlume Cores as three, then the drop-down will be populated with three cores in the Sediment Bed Characteristics frame. The name of each core in the drop-down box can be modified by the user manually.

Water Density can be specified as 1 g/cm³, and Sediment Density can usually be determined as 2.65 g/cm³.   

In Bed Layer Properties and Grain Size Distribution frame, the user can 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.

In SEDFlume Measured Erosion Rates frame, the user needs to fill the first row of the matrix with the shear stress classes (you can see eight columns to fill as the Number of Shear Stress Categories to Calculate Erosion Rates was set to eight at the Sediment Bed tap), then the user may enter the measured erosion rates (cm/s) for each vertical layer with respect to the applied shear stresses (dynes/cm2) for the rest of the matrix.

The sampling location of each SEDFlume core also needs to be entered in Easting (m) and Northing (m) Coordinates for utilizing the Core Assignment features of EFDC+ Explorer.

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After completing the Core Definitions tab, the user may fill the Erosion Rate Matrix (cm/s) for Active & Deposited Sediment Bed in the Erosion Rates tab (Figure 4). This lookup table is used for calculating erosion rates in active & deposited bed layers as a function of their D50 size and an applied shear stress during the model simulation. The user may see that the first row of this matrix present the shear stress classes (dynes/cm²) as the same as the classes specified in the Core Definitions tab (This is the reason why the user needed to complete the Core Definitions tab first). To fill this lookup table, the user may utilize the SEDFlume core test results or can adjust them manually for model calibration.  

Note: EFDC+ Explorer provides a simple quality check for the erosion rate values entered by the user.  Specifically, cells will be highlighted if the erosion rate is not increasing as shear stress is increasing or the erosion rates is not decreasing as the D50 size is increasing. This is only a simple quality check within the user interface, so EFDC+ will still be able to run a model regardless of the quality of input erosion rates.

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