[sam74]

I'll try to keep this short. Initially we have modeled (steady state)what appears to be an inadequate culvert system on a blue line stream. It is at an older government facility. Culverts procede downstream with two 36" to two 30" to two 30" to two 36" RCPs.
The initial model worked out okay and showed flooding on most storm events at most all culverts from top to bottom. It was a simple model assuming all flooding went over road deck and back into the stream. The bad part is that over 30 years of observation shoots holes in our model.
An "expert " reviewed our model and input and saw no issues. Stream monitoring and rain gauges are set to be placed to aid future model adjustment. However, the expert suggested we look at lateral flows into a nearby parallel street to see if this would reduce flooding at road decks. We have three such situations occuring with two 30", two 30", and two 36" RCPs. We sectioned off approximate lateral weir dimensions and developed a rating curve and used this as output from the system for these three occurences slightly upstream of the road decks. We also played with road deck min/max WSE settings to prevent runoff across them.
I finally have everything adjusted so that the program will run and pass all storms optimizations. The first culvert looks good upstream and has WSE close to original model. The downstream hits the channel and goes crazy. 1 and 2 yr storms look reasonable (previously the only flows not crossing the road deck). Then every higher storm event's flow and WSE gets progressively lower. My input in the flow table gets higher but the program begins to ignore the table and ramps the flow of the 50, 100, and 500 yr storm to a constant value of 0.14 cfs. The remainder of the model is a mess after this.
Ever heard of the program ignoring the flow table? Any suggestions out there?