Independent research · No commissions · Nationwide
Floodplain means you build elevated and you buy flood insurance. Floodway means you generally cannot build at all. They are two separate layers on the same FEMA map, and most listings mention neither.
The floodway is the channel of a watercourse plus the adjacent land that has to be kept clear so the base flood can pass. Under 44 CFR 60.3(d)(2), it is drawn so that the base flood is carried without increasing the water surface elevation of that flood more than one foot at any point.
44 CFR 60.3(d)(3) requires communities to prohibit encroachments, including fill, new construction, substantial improvements and other development, within the regulatory floodway. The one exception is where hydrologic and hydraulic analyses performed in accordance with standard engineering practice demonstrate that the encroachment would not result in any increase in flood levels within the community during the base flood discharge. That demonstration is a no-rise certification, and it is an engineer's work, not a counter form.
Under 44 CFR 60.3(d)(4) a community may permit a floodway encroachment that does raise the base flood elevation, but only after it applies for a conditional Flood Insurance Rate Map and floodway revision under 44 CFR 65.12 and receives the Federal Insurance Administrator's approval. Budget time and engineering accordingly.
Open the FEMA flood map for the parcel and turn on the floodway layer separately from the flood zone layer. They are different layers and people routinely look at only the first one.
Zone AE means a one percent annual chance flood with a base flood elevation determined. Zone X is outside that.
Ask two questions in order. Is any part of this parcel outside the flood zone? And does the floodway cross it?
A buyer asked me to look at a lot before making an offer. The listing disclosed a high risk flood zone, which they already knew.
Every FEMA polygon touching that lot was Zone AE. There was no Zone X anywhere on it, not one corner.
A regulatory floodway ran through the middle, roughly 260 feet wide on a lot about 465 feet deep. A little over half the property.
That left a strip on the street side about 160 feet deep, still entirely Zone AE. After the town's setbacks and its minimum house size, the area outside the floodway came to roughly 8,000 square feet. A house fits in that. A house plus a driveway plus a turnaround plus a septic drain field does not, and the lot was not in any sewer service area.
A house had gone up on the neighboring lot the year before, which made building there look routine. That lot had Zone X on it. This one did not.
If the listing mentions an elevation survey in the MLS supplements, ask the listing agent to send it. The seller already paid for it.
Call the county floodplain administrator and ask directly whether a structure and an on-site septic system can be permitted on that parcel. If that answer is no, nothing else matters.
Looking at a parcel near water? I can check the flood zone and floodway layers, the setbacks and the septic question for you, and walk you through what they mean. Request parcel research or read a redacted sample report.
