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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 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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Figure 1  Structure of the SEDZLJ sediment transport model.

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 is considered cohesive, and greater than 200mm is non-cohesive for calculating the probability of deposition.  Also, the size classes greater than 200mm 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 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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The Erosion Rates tab provides the user with the Active and Deposited Sediments Erosion matrix as shown in Figure 56.  Highlighted cells provide a warning to the user that the erosion rate is not increasing with the increasing shear category, or that erosion rates are not decreasing with the increasing grain size. This is simply a QC check for the user and EFDC+ will still run despite the inconsistent values that have been input.

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