Non-residential Structures in the Floodway

[John Schaffer]

Hello all,

I have been asked to poll other jurisdictions with river front parks on how they have, past or present handle new structures that will be located in the Flood Way. Our purposed river front project is to have a bathroom facility (Modular Bld. 20’x20’) to be located in the Flood Way.

The structure will meet ALL Building (IBC) and FEMA (ASCE 24-14) requirements to include structural components for resisting hydrostatic and hydrodynamic loads and the effects of buoyancy as required. The area were the structure is to be located is not prone to flash flooding and always has advanced warning for flooding monitored by our Emergency Management coordinator.

Should a jurisdiction require this structure to be Dry or Wet flood proofed based on it being located in the floodway? FEMA regulations would say it should be Dry flood proofed, but because of the cost to DFP is there any concessions to be made because it is a modular bathroom and still meet the FEMA/FIRM requirements and intent.

Thanks in advance for any responses.

[Jamie Wilks]

Although our community does not have any designated floodways, I deal with floodplain construction daily, including coastal high hazard areas.

From your description, the VCC and ASCE-24 would require this non-residential structure to have the lowest floor elevated to BFE plus one foot –or- dry flood proofed to BFE plus one foot. Wet flood proofing is not an option, except for enclosures below the BFE used for parking, building access or storage. If the structure is elevated to the required height, you will probably run into accessibility issues or challenges.

In addition, you should check your local floodplain management ordinance and 44 CFR 60.3 sub-section (d) for the requirements associated with construction/development in a floodway.

Due to the hazard and dangers associated with floodway development, the requirements are fairly stringent.

An engineering analysis (hydrologic and hydraulic analysis) will be required showing the proposed development will not result in any increased flood levels during the base flood discharge. If the analysis shows an increase in the flood level, your community could apply for a conditional FIRM and floodway revision with FEMA.

Hope this helps.

[John Schaffer]

Thanks Jamie,

Like I said it is a cost issue and what it will take to dry-proof this facility.I am very familiar with 44 CFR 60.3 and as I explained these requirements to our Administration they wanted me to check to see how other jurisdictions handled these types of situations. I can report back that we are interpreting the regulations like other community’s who deal with construction in the flood plain/way. Thanks again Jamie for your comments.

 

 

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