48 inch pipe, how many CFS can it handle

[ACSCorp]

We will be rebuilding a damaged dam that was never built correctly in the first place.

The spillway consisted of a 48 inch vertical corrugated metal pipe. We have completed out hydrology but the question remains how many CFS (cubic feet per second) would have this old system been able to handle. I need to show that this system was flawed to begin with since our 100 year flood calculations come out to 906 CFS and the structure in question overtopped every few years (which should be of no surprise).

 

[GeoPaveTraffic]

You need to hire an engineer familure with dam / spillway design. The capacity of the pipe you have described, varies with the water level above the top of the pipe. Additionally, the capacity may be controled by the outlet of the pipe or some other portion of the pipe.

Why do you believe that the design was flawed? Just because it overtopped doesn't mean there was a flaw in the design.

 

[DamEng1]

The capacity of the old pipe system is likely somewhere around 75-100 cfs.

 

[ACSCorp]

TO GEOPAVETRAFFIC: I stated it was flawed since it overtopped every 2 years or so. It was not sufficient to handle the inflow from the onset. It was built in 1976 by the developer who did consult with an engineer but then went on to do what he wanted. I spoke to the engineer he consulted with and he did design it with a concrete spillway and dewatering valve, none of which exist.

TO DAMENG1: Thanks. Our Q100 is rated at 605 cfs while out PMF is at 1632 cfs. The CMP was woefully inadequate from the get go. Goes to show what happens when you don't listen to the professionals!