Modeling reaches in series
Modeling reaches in series
(OP)
I have a 440 acre watershed that I have broken up into 5 subcatchments. Each subcatchment reports to a reach, and all reaches are connected in series. I am attempting to model a long trapezoidal drainage ditch (8880 feet) to take the stormwater runoff out of the system. There is quite a bit of flow coming out of this system (260 cfs) and I am getting some strange results from the program. The only way i can get this model to "work" (I am still getting error code 62, but I think its ok) is to have the first 2 reaches 10 feet wide and the last three at 25 feet wide. The strange thing is that if I make the first two reaches wider, say 15 feet, then I start getting problems (error 63). This just doesn't make any sense to me as I would think the wider ditch would flow more water, and 25 feet seems excessively wide for the last segments. I am using the dynamic storage-indication reach routing method. Is there any explaination for this?





RE: Modeling reaches in series
Although making a reach wider will reduce the depth of flow, it will increase the tailwater effect caused by the next reach downstream, hence the occurrence of additional warnings.
Basically, you will get some warnings when doing any reach-to-reach routing, and you need to review each situation in detail to determine if you need to use a river modeling system to generate a full water surface profile.
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Modeling reaches in series
RE: Modeling reaches in series
Remember: Each reach is calculated separately without regard to tailwater conditions. So HydroCAD checks the results and warns you of any abnormal conditions that may require closer scrutiny. Messages 61, 62, and 63 indicate progressively more serious tailwater conditions.
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Modeling reaches in series
RE: Modeling reaches in series
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Modeling reaches in series
Peter, correct me if I'm wrong about that.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Modeling reaches in series
Peter Smart
HydroCAD Software
www.hydrocad.net