If your project is located within a Federal Emergency Management Agency (FEMA) floodway, you may be seeking a “no-rise,” which is short for a no-rise certification. In short, a no-rise certification is prepared by a qualified engineer who has conducted a hydraulic analysis that determined your proposed project will not raise the 100-year water surface elevation (WSE) more than 0.0044 feet. For context, a depth of 0.0044 feet is the thickness of approximately two sheets of copy paper. In the following article, I will describe the process of obtaining a no-rise in more detail.

Regulatory Background

A no-rise certification is based on Section 60.3 (d)(3) – Floodway Requirement of the National Flood Insurance Program (NFIP) requirements. According to this section of the NFIP, any project in the regulatory floodway will be evaluated for a potential increase in flood height. An engineering analysis prepared by a qualified engineer is required before a floodplain development permit will be issued for a project. The permitting process involves working with the local Floodplain Administrator and FEMA. This means that it can take several months to over a year to obtain a permit for a project in the regulatory floodway.

What is a floodway?

FEMA defines a regulatory floodway as the portion of a channel or watercourse that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height. In other words, a regulatory floodway is the portion of the floodplain that cannot be disturbed (or “encroached”) without proving the base flood (100-year flow) can be conveyed through the floodway without raising the water surface elevation one foot. The area of the floodplain outside of the floodway is referred to as the “floodplain fringe.”

What is involved in the technical analysis for a no-rise?

The technical analysis for a no-rise involves preparing a hydraulic model using software called HEC-RAS. The HEC-RAS analysis will include an encroachment analysis.

What if I can’t obtain a no-rise?

It is important to note that a no-rise is not guaranteed. There may be ways to increase the chance of obtaining a no-rise such as channel modification or grading the site in such a way that allows more flow conveyance through the floodplain. However, it may be that a no-rise is not possible for your project. If a no-rise certification is not possible, you will need to go through the Conditional Letter of Map Revision (CLOMR)/Letter of Map Revision (LOMR) process. This process involves conducting a hydraulic analysis and evaluating paperwork to request changing the FEMA map to accommodate your project. A CLOMR is prepared before construction, and a LOMR will be prepared once the project is built. The CLOMR/LOMR process tends to be significantly more costly and time-consuming than obtaining a no-rise.

Get in touch

Surf City Hydraulic Engineering is experienced with the process involved in obtaining a no-rise. If you need help with obtaining a no-rise for your project, please reach out to us at paige.brue@surfcityh2o.com.