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HydroCAD Dam outlets routing

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GRAZPFG

Civil/Environmental
Jun 6, 2013
2
I'm modeling a dam which has multiple rectangular notches in a spillway/ b.c. weir. The flow drops down to an adjacent lower box culvert under the road (which can't handle the 100year flow) and then the water would rise up to and over the road (asymmetrical weir). What's the best HydroCAD way to model this...I've tried multiple ponds, pond & cb-pond, single pond. The low box culvert obviously doesn't flow until the spillway weirs flow at their higher level. Modeling as separate ponds does not result in a single/equal pond elevation, which is reality. Any ideas??
 
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What - exactly - is wrong with the results? As a wild guess, you may not have the outlet routing setup properly. Hard to tell without seeing the HydroCAD project file. Are there any warning messages?

Two ponds would probably be the best approach: One for the dam storage and perhaps a zero-storage pond for the box culvert and road overflow. But a single-pond approach may also be possible, especially if the roadway is higher than the dam spillway.

Peter Smart
HydroCAD Software
 
On reflection, you probably need a 2-pond solution in order to handle your outlet setup:

Pond 1 = Dam storage with multiple outlet weirs

Pond 2 = Zero storage with box culvert and road/weir outlet.

This will require a tailwater-sensitive routing procedure (DSI) in order to handle the tailwater effect on the dam created by the roadway. Set your dt to the 0.01 hours and look for any warnings.


Peter Smart
HydroCAD Software
 
Modeling as separate ponds does not result in a single/equal pond elevation, which is reality

why would you have equal ponding elevations upstream and downstream of the dam? even with tailwater effects from the road, the ponding levels should be different due to headloss
 
cvg - I wondered the same thing, but I'm guessing the road is higher than the dam, so the dam will be submerged at high flows?? Details needed here...

Peter Smart
HydroCAD Software
 
Thank you Peter. I used the dynamic S.I. and it seems to work. It's great to learn something new. Good reading in your manual too!
PFG
 
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