0.00 ft.Proven, sealed, defended.
Engineering analysis and sealed certification that proposed development in a regulatory floodway won’t raise the base flood elevation.
What “no rise”actually means.
Zero means zero, reported to the hundredth of a foot.
When development is proposed in a regulatory floodway, federal floodplain rules require an engineering analysis showing the project won’t increase flood heights during the base flood (44 CFR 60.3(d)(3)). In practice that means showing 0.00 ft of rise at every cross-section.
“Development” is broad. Under the federal definition it includes buildings, fill, grading, paving, excavation and storage of materials, not just structures.
Four models.One comparison.
Reproduce FEMA’s effective model and its published results.
Fix errors and add detail, without the project.
Model the site as it is today.
Add the project and compare every cross-section to the hundredth of a foot.
Fill the floodway.Watch the water answer.
Push fill into the floodway, then add a compensating cut that restores the lost conveyance.
The comparison,cross-section by cross-section.
| Station | Existing WSEL (ft) | Proposed WSEL (ft) | Change (ft) |
|---|---|---|---|
| 10+00 | 23.41 | 23.41 | 0.00 |
| 11+50 | 23.88 | 23.88 | 0.00 |
| 12+40 | 24.12 | 24.12 | 0.00 |
| 13+75 | 24.67 | 24.67 | 0.00 |
| 15+20 | 25.30 | 25.30 | 0.00 |
Example output format. Values are illustrative.
Straightanswers.
What if the model shows a rise?
Then the project changes, with less fill or a compensating cut that restores conveyance, or it goes through a CLOMR before it can be permitted.
Who signs the certification?
A licensed professional engineer, with the supporting analysis attached.
Is no-rise the same as compensating storage?
No. No-rise is about flood heights in the floodway. Compensating storage is a local or state requirement in some places to replace flood storage lost to fill. Some projects need both.
Does a fence or a small shed need one?
If it’s development in a regulatory floodway, the community can require it. Ask your floodplain administrator early. We’ll help you read the ordinance.