EFDC Explorer, a pre processor and post processor developed from Dynamic Solutions can be used to faciliate the model input preparation, analysis, calibration etc. There are three versions of EFDC Explorer. They are Web version (free and hydrodynamic part only), trial version (30 days trial with full functions integrated) and full version (hydrodynamic, sediment transport and water quality).
Recently, a latest version of EFDC Explorer is released and the version is EE 6.
You can download EFDC Explorer on this website: http://www.efdc-explorer.com
You can ask several EFDC related and EFDC Explorer related questions on their forum. However, the response from the forum is pretty slow.
Another advantage of using EFDC Explorer is that you can create the simple grids easily and you can import the grid created from several third party softwares.
I hope your simulation process gets rolling.
If you know any other non-commercial software or commercial software that can be used to pre process and post process EFDC model, please write in the comments.