Land records · Parcel maps · October 7, 2026
No-Rise Certificate for Floodway Development
What a no-rise certificate is: an engineer's certification, backed by hydraulic modeling, that floodway work will not raise base flood elevations.
No-rise certificate is a certification by a licensed professional engineer, supported by hydraulic analysis, stating that a proposed development within a regulatory floodway will not increase base flood elevations, floodway elevations, or floodway widths. Under National Flood Insurance Program rules, communities must prohibit encroachments in the floodway unless it is shown that they will not cause any increase in flood heights during the base flood. The no-rise certificate is how that showing is usually documented. It is required before the community issues a floodplain development permit for floodway work. This page is general land-records background, not legal advice.
Why no-rise matters
The floodway is the channel and adjacent land needed to carry flood waters without raising flood heights more than a set amount. Building in it can push water higher upstream or onto neighbors. See floodplain vs floodway.
What the analysis involves
| Step | Description |
|---|---|
| Obtain effective model | Get the hydraulic model used for the FEMA study |
| Duplicate effective model | Confirm it reproduces published results |
| Existing conditions model | Add current site data |
| Proposed conditions model | Add the project |
| Compare | Show zero rise in base flood elevations |
Projects that may need a no-rise certificate
- Buildings or additions in the floodway.
- Fill or grading.
- Bridges and culverts.
- Fences that obstruct flow.
- Utility crossings and roads.
When a rise is shown
If modeling shows any increase, the project cannot proceed as designed unless the community and FEMA approve a map revision, often through a conditional letter of map revision, before construction. Affected owners may need to be notified.
No-rise vs LOMA
A LOMA removes a structure from the floodplain based on elevation. A no-rise certificate shows that floodway work will not change flood heights. They serve different purposes.
Finding the floodway
Floodways are shown on FEMA flood maps as hatched areas within the floodplain. See how to read a FEMA flood map.
Example
An owner wants to replace a small bridge over a creek in a mapped floodway. The engineer runs the effective hydraulic model with the new bridge design and shows zero change in water surface elevations. The engineer signs a no-rise certificate, and the county issues the floodplain permit.
Costs and time
Hydraulic modeling requires an engineer and data, which can be costly for small projects. Early consultation with the floodplain administrator helps clarify what is needed.
Records
No-rise certificates and floodplain permits are kept by the community floodplain administrator and can be requested.
Floodway fringe vs floodway
Outside the floodway, in the flood fringe, communities usually allow development that meets elevation and construction standards without a no-rise analysis, though cumulative rules may apply where no floodway has been mapped. Knowing whether a project is in the floodway itself, not just the floodplain, is the first question to answer.
Bottom line
A no-rise certificate is an engineer’s certification, backed by hydraulic modeling, that floodway development will not raise flood heights. It is required before floodway permits are issued under NFIP rules. Talk to the floodplain administrator early if your project touches a floodway. Explore flood maps via the Platbookmapper map.
No rise certificate FAQ
What is a no-rise certificate?
An engineer’s certification that floodway work will not raise flood heights.
When is a no-rise certificate required?
For development in a regulatory floodway.
Who prepares a no-rise certificate?
A licensed professional engineer.
What if the project causes a rise?
It needs map revision approvals before construction.
Is a no-rise certificate the same as a LOMA?
No, they serve different purposes.