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The primary purpose of using SEDZLJ approach is to simulate better the transport behaviors of sediment materials that are typically complex mixtures of different sized-sediment particles. This algorithm uses a unified treatment for multiple sediment classes with representative particle sizes (regardless of cohesiveness) when simulating the movements of sediments in the water column, changes in sediment bed properties, and sediment flux between the water column and sediment bed (i.e., erosion and/or deposition) based on flow fields computed by the hydrodynamic module (Figure 1). In addition, the SEDZLJ approach can employ site-specific erosion rate data obtained from SEDFlume core tests, which measure the thickness change of sediment bed (mixture) as a function of bed depth and applied shear stress in a controlled flume experiment. A detailed description for of SEDFlume analysis is available in Jones and Lick (2001).
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EFDC+ employs a standard format for SEDZLJ input files, which was originally established by Earl Hayter of USACE, and and EFDC_+ Explorer generates the SEDZLJ input files for EFDC+ simulation run following the standard SEDZLJ input format. Examples of the standard SEDZLJ input files are described in Appendix B 21-24, and three primary EFDC+/SEDZLJ input files are as below:
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core_field.sdf Linkage of SEDFlume erosion properties to model grid cells
EFDC_+ Explorer is is also capable of loading existing EFDC/SEDZLJ input files created by other agencies with different file formats. Specifically, the SEDZLJ approach has widely been used by several water modeling associated agencies including SNL, USACE, and AnchorQEA, but their input file formats tend to be slightly different from the DSI standard format as they are using their own source code. To retain compatibility, EFDC_+ Explorer is designated to load most of those existing SEDZLJ model files and convert them to run in EFDC+.
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Users can activate the SEDZLJ sediment transport module by checking the box Sediment Transport in the EFDC+ Modules tab and selecting SEDZLJ in the drop-list.Then the Sediment Transport sub-tab will appear under the Modules tab as shown in Figure 2.
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Figure 2 Selection of SEDZLJ Sediment Transport Module.
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Users can open the SEDZLJ Sediment and Bed Properties setting window by RMC on the Sediment sub-tab under Modules tab and select Setting. In Major Settings (shown in Figure 3), users may specify the number of sediment bed layers and the number of sediment classes. However, the users should practice a caution when changing the numbers in Major Settings because it may cause loss of existing initial conditions and boundary conditions.
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General Tab
In General tab (shown in Figure 4), users can determine primary computational options for the SEDZLJ sub-model (Figure 3) such as allowing bed morphology changes with hydrodynamic feedback, accounting for bed slope changes in erosion rate calculations, and applying anti-diffusion to vertical sediment concentrations.
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In this tab, Sediment Class Properties frame (Figure 5) allows the users to set the representative particle size, critical shear stresses for erosion and suspension, and settling velocity for each sediment class. These transport parameters are used to simulate the behaviors of the sediments in active movements (sediment materials in water column layers and active sediment bed layer). As SEDFlume test data are generally reported in CGS units, EFDC_+ Explorer also employs the unit of dynes/cm2 for critical shear stresses to be consistent with the reported data.
In Sediment Information frame, there is Sediment Info button reports the critical shear stresses and settling velocities computed based on the particle sizes entered in the Sediment Class Properties table. The critical shear stresses and settling velocities are calculated using Van Rijn’s equations (Van Rijn, et al 1984), and the resulting values are provided in the pop-up window. However, those values are calculated only to provide users a guideline for those transport parameters, and and EFDC_explorer + Explorer would not use the values in the pop-up window when generating the SEDZLJ model input file (bed.sdf).
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Sediment Bed Tab
In Sediment Bed tab (Figure 6), users can specify the sediment properties for Active & Deposition Sediment Bed Layers including Active Layer Thickness Multiplier, Number of Sediment Size Categories, Number of Shear Stress Categories to Calculate Erosion Rates (only for Erosion Rates Option 1), and Bedload Options.
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In Erosion Rates tab ( shown in Figure 7), users can specify the Active and Deposited Sediments Erosion Matrix, which is the lookup table that determines erosion properties for active & deposition bed layers as a function of their D50 size. The matrix format displayed in this frame varies depending on the Erosion Rates Options selected in General tab, and detail descriptions for each option are described in sections: Erosion Rates Option 1, Erosion Rates Option 2, and Erosion Rates Option 3.
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Core Definitions Tab
In Core Definitions tab (Figure 8), users can enter several erosion rate datasets acquired from SEDFlume core tests, which will be used to define site spatially varying erosion properties of parent-bed layers.
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Core Assignments Tab
Core Assignments tab (Figure 9) helps users to assign the SEDFlume core definitions for physical and erosion properties to model grid cells. This process is to define the horizontal distribution the SEDFlume properties over the model domain.
The users may check the box for Allow Core Definitions on a Cell by Cell Basis and can set the Default Core Number so that that EFDC_+ Explorer assigns the default core definition to the cells which fall outside the SEDFLume data available region.
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With using the Assign Core Numbers using Polygons with ID’s option, the users can assign the SEDFlume core definitions to the cells within the area specified as a polygon using a P2D file. The P2D file begins with a single line header for SEDFlume core ID, and the following lines present the X and Y coordinates to define the corresponding polygon area. EFDC_+ Explorer will assign the specified core definitions to the group of cells that are located inside the polygon.
Through this process, EFDC_+ Explorer will generate the associated input file (core_field.sdf) following either DSI Standard format (I, J, and Core Number) or Sandia Lab Standard format.
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The SEDZLJ wave options can be set by the user to impact the bed shears (Figure 10). The Wave Action Options dropdown provides three options: No Wave Action, Wind Wave (SEDZLJ), and STWAVE. While these options can use the EFDC+ internal wind waves, at this stage they only impact the boundary layer. It is anticipated in the future that SEDZLJ will be updated so that it can use the internal wind waves or external wave linkages in the EFDC wave sub-model, however, at this stage this option is not available.
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Miscellaneous Tab
In Miscellaneous tab (Figure 11), users can set Skin Friction Options and select to use constant bed shear stress or not. The users should refer to the SEDZLJ user manual for more information on Skin Friction Options and Use Constant Bed Shear Stress options.
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