The Federal Emergency Management Agency (FEMA) floodplain maps in Oakville were last updated in 1976. In a rural, unincorporated town in Napa County, the Oakville Cross Road Bridge replaced the almost 100-year structure that preceded it. Schaaf & Wheeler was contracted by Napa County to conduct a No-Rise Study for the new bridge. After extensive analysis a Letter of Map Revision (LOMR) emerged to rectify FEMA’s inaccurate Flood Insurance Rate Maps (FIRMs).
The No-Rise Study analyzes the impact created by new bridge and aims to limit impacts within the regulatory floodway. Schaaf & Wheeler’s hydraulic models of the Napa River didn’t align with the FIRM’s. To tie into the FEMA mapping, models were extended an unprecedented 6 miles along the river. The simple analysis of the bridge reconstruction project evolved into a LOMR where public meetings were held to inform residents of the newly uncovered flood risks.
Schaaf & Wheeler produced a LOMR that updated the current effective Special Flood Hazard Area (SFHA). This shifted the 100-year floodplain and floodway to more accurately represent flood risks in the area.