The most state-of the-art sediment transport sub-model for EFDC is the SEDZLJ module that uses Sedflume data to determine erosion rates has been developed by Sandia National Laboratories. A detailed description of the SEDZLJ implementation in EFDC code is available in Sandia National Laboratories Environmental Fluid Dynamics Code: Sediment Transport User Manual (Thanh et al. 2008). The SNL approach, shown in Figure 1, accounts for multiple sediment size classes, has a unified treatment of suspended load and bedload, and appropriately replicates bed armoring. The resulting flow, transport, and sediment dynamics in the model is an improvement to on previous models because this model directly incorporates site-specific erosion rate and shear stress data, while maintaining a physically consistent, unified treatment of bedload and suspended load.
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As can be seen in Figure 1, SEDZLJ does not distinguish between cohesive and non-cohesive groups for erosion, deposition and transport. In this sub-model, any particle size less than 200mm 200 mm is considered cohesive, and greater than 200mm 200 mm is non-cohesive for calculating the probability of deposition. Also, the size classes greater than 200mm 200 mm can be transported by bedload. The overall goal of SEDZLJ is to better represent sediment transport of typical sediments, which are a complex mixture of grain sizes with associated complex behavior. For this reason the SEDZLJ approach is now EPA’s preferred standard for contaminant sites.
EE can load most existing EFDC/SEDZLJ projects. Many of these existing SEDZLJ projects use slightly different formats, including those from SNL, USACE and AnchorQEA. Most of these existing projects can now be loaded by EE and saved out to run in EFDC+. EFDC+ uses a standard DSI format of the input files that was originally developed by Earl Hayter of USACE. DSI has developed a standalone AnchorQEA to EFDC+ converter since their files are completely as these files are non-standard EFDC formats. Contact DSI for more information about this.
Examples of the SEDZLJ input files can be found in Appendix B 21-24 . The primary input files for EFDC+ running the SEDZLJ sub-model are:
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CORE_FIELD.SDF Assigns a cell to a core profile where each core has certain properties)
For both the conventional EFDC and SEDZLJ sediment models, the user may set Major Settings for the number sediment layers and number of sediments. However, these values should be changed with caution as it may result in loss of initial conditions and boundary conditions.
In the following sections, options available in the form SEDZLJ Sediment and Sediment Bed Properties are described. The SEDZLJ sediment model is activated from the EFDC Modules form by RMC on Modules tab of Model Control form. The user should first check on (SEDZLJ) Sediments check box and then the Sediment sub-tab will appear under the Modules tab as shown in Figure 2.
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Figure 2 Active Module tab - SEDZLJ sediment transport sub-model.
RMC on the Sediment sub-tab, select Setting to open the SEDZLJ Sediment and Bed Properties setting form.
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The Date/Time to Start Sediment Transport allows the user to run the model without erosion and deposition active until the model is stable. After model is stable, the sediment transport is fully activated from the specified time. The Deposition Limit of water Water Column Sediments is a value from 0 to 1. This represents the minimum fraction of sediment in the bottom water layer allowed to deposit in a single time step. Setting this to zero would cause 100% of the amount to be deposited in one time step, however, this is also dependent on the settling rate specified. The Minimum Water Depth for Shear Stress Updates (m) is the minimum water depth of a grid cell that allows calculating the shear stress.
The Erosion Rate Options frame allows the user to select one of three options with different types of erosion rates matrix data. Details of these options are described in Erosion Rates Option 1, Erosion Rates Option 2 and Erosion Rates Option 3 section.
The Temporally Varying Erosion Rate Parameters frame is an alternative option that allows the user to generate a erosion rate matrix from an external file like such as ASCII or Binary binary files.
The Hard Bottom Option frame allows the user to select in which area bed processes are activate activated or not . (Assign assign the value to 0 for to deactivate all bed processes for cell the cells and 1 for allows so that all bed processes are activateactivated).
Figure 3 SEDZLJ sediment transport sub-model – General tab.
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In the Sediment Information frame shown in Figure 4 there is Sediment Info button which reports the critical shear stress for grain sizes used in the Sediment Properties for the Sediment Distribution table. These calculations for the critical shear stress are based on the equations from Van Rijn (Van Rijn, et al 1984) which use uniform grain size calculations and are provided for the user’s information. These numbers do not have any impact in the actual model calculations. The Initialize Defaults button uses the values calculated here to provide initial values for the critical shear stresses for erosion and deposition, though the user would normally have measured data for these.
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In the Sediment Bed tab shown in Figure 5, the Active & Deposited Sediment Characteristics frame allows the users to specify the Number of Deposited Sediment Classes, as well as the Number of Shear Stress Categories to Calculation Erosion of Newly Deposited Sediments and the number of active layer multiplier. Note that SEDZLJ allows for a different number of sediment classes for the sediment distribution and erosion characteristics.
The Bedload Options frame allows the user to select computing bedload for coarser classes or not and to set its parameter settings
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The Erosion Rates tab provides the user the Active and Deposited Sediments Erosion Matrix . Which data are displayed in this frame depend depends on the selection of Erosion Rates Options in General tab.
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The Core Definitions tab, shown in Figure 6 is where the user defines the Number of SedFlume Cores, and thenassigns the key parameters associated with each core. For example, if the user sets the number sedflume cores to two, then in the Core Parameter frame the drop-down will be populated with two cores. The name of each core are is set in the text box under Sediment Erosion Characteristics frame
For each layer core, the user should set the critical shear stress and bulk density as well as percentage of the grain size distribution in Bed Layer Properties and Grain Size Distribution frame. In the SEDFlume Measured Erosion Rates frame, the user should define the initial bed erosion rates for each layer, which data is used in this table depend depends on the selected option of Erosion Rates Options in the General tab.
Figure 6 SEDZLJ sediment transport sub-model – Core Definitions tab.
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If the standard SEDZLJ wind wave option is used then the EE wind wave option is not used. In this case the user must ensure they have all the correct files such as FETCH.INP refer . Refer to the SEDZLJ user guide for details on this format. Conversely, if the STWAVE option is selected then that correctly formatted STWAVE files are required.
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1.9 Miscellaneous Tab
The Miscellaneous tab is shown in Figure 8. In this section, user can set Skin Friction Options and select to use constant bed shear stress or not. The user should refer to the SEDZLJ user manual for more information on Skin Friction Options and Use Constant Bed Shear Stress options.
Under Class Maximum Grain Size frame, the table shows the maximum grain size of each sediment class from input data.
Figure 8 SEDZLJ sediment transport sub-model – Miscellaneous tab.
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