Is a "No-Rise" Cert Needed to Clean-Out (Deepen) an Existing Pond on A Flood Plain?

[KurtKrog]

A private property owner has a small (60' by 120') shallow pond sitting on a FEMA regulated flood plain that is next to a larger lake (also fairly shallow) that has a floodway running through it. The owner wants to clean-out the small pond, dredging it to make it deep enough to aerate and keep clean and safe.

The local FEMA admin is says a full H&H Study needs to be done and a "No-Rise" Cert filed. The owner just wants to dig out the small pond and carry the dredged material to non-floodplain parts of the property (so no elevation of the floodplain). Several engineers have said just digging the pond deeper or even widening it a bit cannot increase the 100-year flood risk.

There is a dam on the other side of the larger lake that sets the lake's water level. Do you agree and have any authority supporting that digging out an existing pond on a floodplain doesn't create a flood risk and shouldn't need a H&H Study for a "No-Rise" Certificate?

Or do you know an Ohio licensed engineer that would run the FEMA Model the owner has? Thanks - kurtkroger@yahoo.com

 

[ACtrafficengr]

Is it really a pond, or could you call it stormwater detention, and call it required maintenance instead of dredging?

It might be a bit of a stretch, since detention ponds are not supposed to be in floodplains.

My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. -

http://xkcd.com/319/

 

[KurtKrog]

Thanks ACtrafficengr - I agree. After studying floodplain issues more, I'm reshaping the analysis to accurately reflect basically what you are saying, which shows it is not "development" of anything in the floodway or even on the floodplain. It is actually something people do to mitigate (off-set) developments to assure a net no-rise. Plus, there is the whole "hydraulic shadow or conveyance shadow" concepts and just digging a pond deeper is clearly maintenance within the ultimate shadow zone (namely, underground, below the floodway conveyance zones. Digging 30 inches or 30 feet deeper simply can't physically increase the 100-year flood risk or impede the the flood flow/conveyance. Common sense and simple facts should not take a back seat to $$$ CYI computer analysis. Thanks