Sediment Transport Questions

EFDC_Explorer
1

Hello,

I have a problem running sediment transport simulation. I used an example to
setup the river I would like to simulate, hydrodynamics are fine, but
sediment transport crashes after a couple of iterations. The example I used
is the Green River and input files have similar values and settings. The
Green River runs fine but my river crashes.

Thanks in advance for your help,

PV

2

Dear P,

There are so many reasons why a sediment transport model would crash, even
if the hydrodynamics runs OK. Start simple, i.e. one cohesive class and
zero the sediments in the sediment bed, and learn how the model behaves. As
you get each level of model to run, increase your level of complexity until
you get to the level needed by your site conceptual model.

That said, you are probably eroding the bed too fast, which usually causes
negative depths to be computed (I did not look at your example yet). Making
sure the sediment time step is not too big will help.

Regards,

EFDC_Explorer Development Team

3

Hello,

Ok I went back to 1 grain size and that also leads to a crash, forrtl: error
(73): floating divide by zero. routine _TMSR line 835 TMSR.for

The weird thing is that this seem to happen after a fixed number of
iterations. Because if I half or double the time step the time in days until
the crash halves or doubles too.

Any suggestions on this?

P

4

Sounds like your inflow time series of sediments is bad.

5

Thanks I will look into that.

Could you please tell me if there is an option to set bedload transport
(and) equilibrium transport at the upstream boundary? If so how?

Thanks a lot,

P

6

There is not a direct method to assign incoming bedload BC’s. You can set up donor cells at the upstream end of each branch to address this.