No-Rise / No-Impact Certification
The client requested to perform No-Rise / No-Impact evaluations for proposed new buildings on two lots that may involve encroachment into FEMA designated flood plain on Imperial River located in the City of Bonita Springs, Lee County, Florida.
- CLIENT
- Private Client(sub-consultant to Grady Minor)
- YEAR
- 2021
- APPLIED SKILLS
- H&H Modeling: Data mining & processing; conceptualization & setup
- CONSULTING AREAS
- Stormwater management
Flooding assessment - SOFTWARE
- HEC-RAS, ArcMap.
Specifics
LAGO refined the corresponding FEMA HEC-RAS model available from the latest Flood Insurance Study (FIS) for Lee County. The refinement included a higher spatial resolution by inserting new cross sections around the parcels to be developed. These cross sections were designed by combining river surveyed cross sections and high-resolution DEM at the banks. Model tolerances were also reduced to diminish numerical errors.
Then, the refined model cross sections are modified to include the proposed grading and the new buildings.
The comparison of the 100-year water surface elevations from the pre- and post-development models showed a difference of 0.00 ft at the cross-sections adjacent to the development site, which indicated no rise of flood stages caused by the development.
Outcome
A No-Rise Certificate was issued by one of our Professional Engineers for the proposed development. The certificate was accompanied by support files detailing the evaluation performed.