hec hms riser pipe

[hunter82]

I am attempting to model a riser pipe in Hec-Hms. I know that at the beginning stages of the pipe flowing, it functions like a weir, with the circumferece of the pipe equal to the length of the weir, but as the water level increases the riser pipe begins to flow full and it is modeled like an orifice.
My question is can this be modeled in hec-hms or do I need to find another program to perform the combination modeling.

 

[gbam]

Not sure if HMS can model this for you. However, one can create and combine a rating table and code it into HMS. I personnaly do not use HMS. I have always used HEC-1 or my own spreadsheet to analyze that same scenario. When ever I come across this riser condition, I create a rating table for discharge vs. stage.

 

[cvg]

try the following link to download a good spreadsheet which will do the calculation for your riser.

Hydraulic computations for Drop Inlet Spillways

http://www.ecy.wa.gov/programs/wr/dams/guide.html

 

[RWF7437]

You can also model this in both HydroCad (advertised on this website) and in Hydraflow Hydrographs 2007. Google both. There are other similar programs available at reasonable cost and most can do many other outflow device configurations.

good luck