Published
Building in the Floodplain Overlay: where clearing and grading suddenly need a permit
An overlay that changes what counts as development
Corridor ground near the river carries a second set of rules on top of its zoning. Fremont County calls it the Floodplain Overlay District, and the most important thing about it is not the building standards. It is that the overlay changes what needs a permit at all.
“Development in the FOZD shall be by permit only... For the purposes of this chapter, application shall include any activity that may potentially affect flood flows. This includes all land disturbance (including clearing, grading, and the construction of fills), as well as building construction. Some Applications that are exempt from permit requirements in other areas must obtain a permit in the FOZD.”
— Fremont County Development Code, 2011 Edition (Ordinance 2011-04), section 7.03, Additional Permit Requirements. Retrieved 19 August 2026
That last sentence is the one to carry away. Work that would be nobody's business on an ordinary corridor lot — pushing up a fill, clearing a patch, regrading for drainage — requires a permit inside the overlay. The exemptions you might otherwise rely on do not travel into it.
Where the boundary comes from
The overlay is not drawn by the county. It consists of all Special Flood Hazard Areas identified on FEMA's Flood Insurance Rate Maps for Fremont County, adopted by reference as a supplement to the official zoning map.
There is a wrinkle in how the code says this, and it is worth knowing rather than glossing. The chapter refers to the most current Flood Insurance Rate Maps, and then adopts by reference a Flood Insurance Study dated 18 March 1991 together with its accompanying maps. Those two phrases do not obviously say the same thing. If a parcel's flood status matters to a purchase, the sensible question to the county is which mapping they are actually applying to it today, and the sensible parallel check is FEMA's own current map for the parcel.
What you sign
Every permit application in the overlay must be accompanied by a signed and dated acknowledgement. It is short, and it is unusually candid for a government form. In substance, the applicant confirms understanding that:
- The degree of flood protection required is considered reasonable for regulatory purposes and is based on scientific and engineering considerations — but larger floods can and will occur.
- Projected flood levels at the site may be increased by man-made or natural causes.
- The ordinance does not imply that land outside a special flood hazard area, or permitted uses within one, will be free from flooding or flood damage.
- The ordinance creates no liability on the part of the county, its officers or employees, or the Federal Insurance Administration, for flood damages.
Nobody should be alarmed by that; it is standard floodplain administration and it is honest. But it is worth reading before signing, because it is the county telling you plainly that compliance is not the same as safety.
What has to be submitted
| Requirement | When it applies |
|---|---|
| Elevation of the lowest floor, including basements, of all proposed buildings | Every application in the overlay |
| Elevation to which any existing or proposed building has been or will be flood-proofed | Every application in the overlay |
| Certification by an engineer or architect that the flood-proofing methods comply | All buildings other than single family dwellings |
| Description of any watercourse alteration, plus proof that all state or federal permits for it are approved | Where a watercourse will be altered or relocated |
| Base flood elevation data provided by the applicant | Subdivisions or applications with 50 or more lots or dwelling units, or five or more acres |
The five-acre threshold is the one that catches corridor buyers, because it is not a subdivision threshold. A single application on five acres or more triggers the requirement to supply base flood elevation data — which is survey and engineering work, with a cost and a lead time.
How the building has to be built
The performance standards inside the overlay are the familiar FEMA ones, and they bear on the quote rather than only on the drawings.
- Anchoring. New construction and substantial improvements must be anchored to prevent flotation, collapse or lateral movement. Manufactured homes are named specifically, and the code mentions over-the-top or frame ties to ground anchors among acceptable methods.
- Materials. Construction must use materials and utility equipment resistant to flood damage, by methods that minimise it.
- Service equipment. Electrical, heating, ventilation, plumbing and air conditioning equipment, and other service facilities, must be designed, elevated or located so as to prevent water entering or accumulating within them during flooding.
- Water and sewage. New and replacement potable water systems must be designed to prevent infiltration of flood waters, and the same requirement applies to sewage disposal systems.
Item three is a design decision, not a detail. Where the mechanical equipment goes is settled early, and a plan that puts the furnace and the panel in a low space is expensive to revise once the slab is poured — the same category of early decision as footing depth.
The overlay does not override the stream corridor rules
One provision saves a good deal of confusion. The chapter says the ordinance's stream and lakeshore corridor performance standards impose requirements that are more stringent than the floodplain chapter's own, and that the most stringent requirements apply.
So being outside the mapped floodplain does not mean being free of water-related setbacks, and being inside it does not mean the floodplain chapter is the only thing to satisfy. They stack, and the tighter one governs on any given question.
What the Administrator does that affects you
Two of the Administrator's floodplain duties are worth knowing because they generate paperwork you will want later.
The Administrator must maintain a record of the actual elevation of the lowest floor of all new or substantially improved buildings, and whether the building contains a basement, and must maintain a record of flood-proofing certifications. That record is the county's, and it is the sort of thing that becomes valuable when a lender or an insurer asks a question years afterwards. Ask for a copy of what goes into it at the time, rather than trying to reconstruct it later.
The Administrator must also determine that all required state and federal permits have been obtained before reviewing any application in the overlay. That is a sequencing rule: the county will not start until the other agencies have finished, so an application filed in the wrong order simply waits.
Before you buy corridor ground near water
- Is any part of the parcel in a mapped Special Flood Hazard Area, and on which map version?
- Is the parcel five acres or more, which triggers the base flood elevation data requirement on its own?
- Does the plan involve any fill, clearing or regrading, and has anyone priced the permit that work now needs?
- Where will the mechanical equipment sit, and does the design already reflect the elevation requirement?
- Is a watercourse alteration contemplated, and if so, which state and federal permits does it need first?
- How do the stream corridor setbacks interact with the flood mapping on this particular parcel, given the most stringent rule governs?
- Has the flood question been settled before the permit path starts, since whoever files the building permit will be working to whatever the overlay requires?
- Will a lender or insurer want the elevation certificate, and is somebody producing it as part of the build rather than after it?
Common questions
What is the Floodplain Overlay District?
An overlay consisting of all Special Flood Hazard Areas identified on FEMA's Flood Insurance Rate Maps for Fremont County, adopted by reference as a supplement to the official zoning map. It carries its own permit requirements and building performance standards on top of the underlying zone.
Does clearing or grading need a permit inside the overlay?
Yes. The code defines application for this chapter as any activity that may potentially affect flood flows, including all land disturbance such as clearing, grading and the construction of fills, and states that some applications exempt from permits elsewhere must obtain one in the overlay.
Which flood maps does the county actually use?
The chapter refers to the most current Flood Insurance Rate Maps and separately adopts by reference the Flood Insurance Study dated 18 March 1991 with its accompanying maps. Those phrases are not obviously identical, so it is worth asking the county which mapping it is applying and checking FEMA's current map in parallel.
What do I have to submit with an application?
The elevation of the lowest floor including basements, the elevation to which anything has been or will be flood-proofed, and for buildings other than single family dwellings a certification by an engineer or architect that the flood-proofing complies. Watercourse alterations need a description plus proof of state and federal permits.
When do I have to provide base flood elevation data myself?
For subdivisions or other applications that include 50 or more lots or dwelling units, or five or more acres. The acreage threshold applies to a single application, so it is not only a subdivision requirement.
What is the acknowledgement I have to sign?
A signed and dated statement confirming you understand that larger floods can and will occur, that projected flood levels may be increased by man-made or natural causes, that the ordinance does not imply any land or permitted use will be free from flooding, and that it creates no liability on the county or the Federal Insurance Administration.
Do the stream setbacks still apply inside the floodplain?
Yes. The chapter states that the ordinance's stream and lakeshore corridor performance standards are more stringent than its own and that the most stringent requirements apply. The two sets of rules stack rather than replacing one another.
Does the county keep a record of my floor elevation?
It is required to. The Administrator must maintain a record of the actual elevation of the lowest floor of all new or substantially improved buildings, whether the building contains a basement, and the flood-proofing certifications. Asking for a copy at the time is easier than reconstructing it years later.
Can I apply to the county before getting other agency permits?
Not usefully. The Administrator must determine that all required state and federal permits have been obtained before reviewing any application for a permit in the overlay, so filing out of order means waiting rather than progressing.