Culverts in Zone AE
Culverts in Zone AE
(OP)
I have a existing roadway culvert in zone AE. We are proposing improvement on the roadway (widening) but decided (higher officials) to leave in AE zone. Existing culvert is 2-60" pipes for 2.2k cfs flow at culvert. The 100yr flood elev (HEC-RAS) at the culvert determined is 4' above the pavement (different study). Do one has to design the culvert for the 2.2k cfs or can allow overtopping and hence fewer and smaller culvert sizes.





RE: Culverts in Zone AE
It seems like the community public works official needs to determine whether roadway inundation in post-project conditions is acceptable, or not. Whether it is or not may depend on how heavily the road is used, adjacent properties (and old or potentially new flooding claims), planned development in the area, etc. etc.
RE: Culverts in Zone AE
RE: Culverts in Zone AE
RE: Culverts in Zone AE
Where you will run into trouble if you start undersizing the culvert, is that the road will overtop more frequently. If you're trying to VE the size of the culvert, it would be in your best interests to run an analysis of the 1 year, 2 year, 5 year, etc storms to get an idea how often it's going to overtop.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Culverts in Zone AE
If you are asking whether future improvements are allowed to overtop, then I think the answer is yes and your PW official needs to tell you (or perhaps you need to convince them) of what that frequency should be. It seems like CVG and beej67 have provided good guidelines to that end, above.
If you are asking how to size culverts that are going to be overtopped, then it's a matter of calculating your total flow and then determining your culvert capacity and weir flow capacity.
Sorry if I'm confused.
RE: Culverts in Zone AE
RE: Culverts in Zone AE
RE: Culverts in Zone AE
Robert Billings
www.newrivereng.com