Required Discharge
Required Discharge
(OP)
Hello all,
I have a basin with a known volume. I know the peak discharge and Time of Concentration for my drainage area for my design storm. How do I calculate the required discharge from my basin to prevent it from overtopping during the design storm? Any help is greatly appreciated.
Scott
I have a basin with a known volume. I know the peak discharge and Time of Concentration for my drainage area for my design storm. How do I calculate the required discharge from my basin to prevent it from overtopping during the design storm? Any help is greatly appreciated.
Scott
RE: Required Discharge
If this is an existing basin that you are evaluating then route your inflow hyd through under existing condition and determine the overtopping flow by using a rating curve for a weir and culvert(if there is a culvert). The flow rate that you determine to overtop is approximately the increase in flow rate that you will need to add to your culvert capacity.
I am guessing at your situation so more information would be helpful!
RE: Required Discharge
Example:
Existing sediment basin volume is 142,000 cuft, and peak discharge is calculated at 349 cfs. Is there an equation to calculate the required discharge to provide a minimum 30 minutes detention time without the basin overtopping?
RE: Required Discharge
You could construct an overtopping spillway and leave the culvert small. This would allow de-silting and also handle larger flows.
RE: Required Discharge
In the past I have had to calculate detention times for basins, so this should work:
Vol / time = flow
142000 ft^3 x 1/30 min x 1 min/60 sec = 78.8 cfs
Hope that helps.
RE: Required Discharge
Thanks for the input. However, would that 78.8 cfs discharge be sufficient to prevent my basin from overtopping during a 25 yr 24 hr storm, generating a peak discharge of 349 cfs?
RE: Required Discharge
RE: Required Discharge
As far as overtopping, you would have to adequate storage in the basin to compensate for the additional inflow (78 vs 349). Tr-55 estimate approx. 8.7 Ac-ft of total storage would be require in the basin to maintain a release rate of 78 cfs. This too is only a estimate, but it is another starting point to work from.