My 1D model if 15,000 feet for a small stream/canal and bridge worked fine until I had to add 1.5 miles downstream. The downstream has a very straight section that has an abrupt, tight turn of about 100 degrees. In this area flow reduces from 840 cfs to 87 cfs for a thousand feet then increases back up to 830 cfs. The Water Surface Elevation doesn’t change really until the cfs goes back up, then it drops 0.4′. The area of reduced flow may be due to split flow.
As for the profile, at the lower flows, the EG and wse occilates wildly where the wse is almost at reach bottom and then it goes straight up 8′. The EG about 30′.
Sections are about 100′ apart. Maybe too close. I tried deleting a few where the abrupt turn is, but it didn’t help.
I tried adjusting the computation time step and adjusting the Theta number. Will look at Htab next. It is a pretty flat reach.
I was going to add a few pngs but don’t see any button to add files.
I am hoping someone had this happen and knows how to fix it.