According to my experience, modeling the sediment transport in Flow-3D needs a considerable time and computational efforts while the accuracy of your modeling ,depending on the geometry and boundary conditions, is about 10 to 20 percent in the best case.

I used Flow 3D some couple of years. In spite the (somehow) ambiguity of the user manual, the solver is very powerful. Although not the most friendly-user softer on the market, it is always a good choice.

If you are just starting, I would recommend you to use FLOW-3D. If you have a project that needs a bespoke model (and you have a lot of time), you shall try OpenFOAM.

Flow 3d is suitable