West Fork Issaquah Creek, near Seattle, Washington. It’s a couple miles long in a low gradient valley. Flooding is a problem for some of the residents. I’ve posted parts of the 1D/2D model over the last few months and, with your help, have improved it – my first work in 2D. Thank you!
I’ve got it running a 100-year 4-day flow volume during a 10-day model period. Full momentum, Courant time step criteria 0.4 to 1.0, theta is 0.6 in 1D and 2D. It all looks pretty good, but 1% of the flow volume is lost.
No water surface elevation or flow error warnings display while performing the unsteady flow simulation, using default thresholds. The summary err, warn, etc. list is chock full of flow ratio warnings, but that is to be expected. Flood waters go overbank to the 2D flow area.
The 2D flow area error is essentially 0%, but the total volume accounting has an error of 1.08%. I suspect volume is slipping out across 11 lateral structures along the banks, about a mile of them. Annual peaks down at the mouth push past 100 cfs in maybe half the years. I have the minimum 1D/2D flow tolerance set at 10 cfs, and I’m guessing that tightening the minimum flow tolerance threshold down might fix some of the leak. What do you think?