ctbailey
Civil/Environmental
- May 11, 2005
- 50
Hi. I know, this topic has been beaten badly, but i still have a question.
I have a simple driveway culvert that I have modeled as a reach, and also as a catchbasin pipe outlet.
The pond outlet model indicates the culvert is undersized, and the flood elevation is breached. (I set the flood elevation as the centerline of the road.)
The reach model indicates the culvert has excessive capacity, based on the expected peak flow, and the culverts' manning capacity.
So I set the auto-resize to on, performed the calculation, and both culverts are resized, to the top of pipe crown.
However, the pond still overtops the road. Why doesn't the pipe get resized to NOT allow overtopping?
Second question: (Theory) why does the "pond" method produce such a different capacity of the culvert? The manning capacity of the pipe is far greater than the peak flow, and the inlet condition setting in the pond outlet screen effects the pipe very little. So I would expect my "no storage" pond would pass all the flow into the culvert, and no headwater at all would occur. However, in my parralell analysis my "no storage" pond is overtopping the road.
Very curious.
Thank you very much.
___
Craig T. Bailey, PE
I have a simple driveway culvert that I have modeled as a reach, and also as a catchbasin pipe outlet.
The pond outlet model indicates the culvert is undersized, and the flood elevation is breached. (I set the flood elevation as the centerline of the road.)
The reach model indicates the culvert has excessive capacity, based on the expected peak flow, and the culverts' manning capacity.
So I set the auto-resize to on, performed the calculation, and both culverts are resized, to the top of pipe crown.
However, the pond still overtops the road. Why doesn't the pipe get resized to NOT allow overtopping?
Second question: (Theory) why does the "pond" method produce such a different capacity of the culvert? The manning capacity of the pipe is far greater than the peak flow, and the inlet condition setting in the pond outlet screen effects the pipe very little. So I would expect my "no storage" pond would pass all the flow into the culvert, and no headwater at all would occur. However, in my parralell analysis my "no storage" pond is overtopping the road.
Very curious.
Thank you very much.
___
Craig T. Bailey, PE