Flood Zones: Costa Mesa vs Mission Viejo
How do flood zones rules compare between Costa Mesa, CA and Mission Viejo, CA?
Mission Viejo has fewer restrictions than Costa Mesa.
Costa Mesa, CA
Orange County
Costa Mesa participates in the National Flood Insurance Program (NFIP) and regulates floodplain development under Title 13 (Planning, Zoning and Development), Chapter V, Article 8 of the Costa Mesa Municipal Code. Sections 13-81 through 13-83 govern uses permitted in designated floodway fringe and Special Flood Hazard Areas (SFHAs) shown on FEMA Flood Insurance Rate Maps, development standards for floodway areas, and exceptions. The Santa Ana River forms Costa Mesa's western boundary and Upper Newport Bay borders the city's eastern edge - both are primary regulated drainages. State authority for floodplain regulation derives from California Water Code Sections 9100 et seq. (Flood Control) and Section 8400 (state floodway designation). FEMA's currently effective Orange County FIRM panels apply to all floodplain determinations within city limits.
View full Costa Mesa rules →Mission Viejo, CA
Orange County
Mission Viejo participates in the FEMA National Flood Insurance Program (NFIP) and enforces minimum floodplain management standards adopted under Ordinance 93-118. Properties in Special Flood Hazard Areas (SFHAs) along Aliso Creek and Oso Creek must meet FEMA elevation and building requirements, and Elevation Certificates are required for new construction in mapped Zones A, AE, AH, AO, and similar designations.
View full Mission Viejo rules →Key Facts Comparison
| Fact | Costa Mesa | Mission Viejo |
|---|---|---|
| Local Code | Costa Mesa MC Title 13, Chapter V, Article 8 (Sections 13-81 to 13-83) | - |
| State Law | Cal. Water Code Sections 9100, 9620, 9650 | - |
| Federal Law | 44 CFR Parts 59-72 (NFIP) | - |
| Primary Drainages | Santa Ana River (west), Upper Newport Bay (east) | - |
| Flood Maps | FEMA Orange County FIRM (msc.fema.gov) | - |
| NFIP Status | Participating community | Participating community with CRS premium discount |
| Permit Authority | Costa Mesa Development Services / Building Division | - |
| Elevation Cert. | Required for new/substantially improved structures in SFHA | - |
| Adoption | - | Mission Viejo Ordinance 93-118 (floodplain) |
| SFHA Standard | - | 1% annual chance flood (100-year base flood) |
| Mapped Zones | - | A, AE, AH, AO along Aliso Creek and Oso Creek |
| Elevation Cert | - | Required for new builds in A1-A30, AE, AH, AO, V |
| Federal Rule | - | 44 CFR 60.3 NFIP minimum standards |
| State Authority | - | Cal. Water Code §§9100, 9620, 9650 |
| City Engineer | - | Public Works (949) 470-3079 |
Highlighted rows indicate differences between cities.
Costa Mesa FAQ
Mission Viejo FAQ
How do I find out if my Mission Viejo property is in a FEMA flood zone?
Use the City's GIS system (search by address or APN, then view the FIRM panel) or the FEMA Map Service Center at msc.fema.gov. The City Engineering Counter at City Hall and the Mission Viejo Library also keep paper FIRMs available for review. For a written flood zone determination, contact the City Engineer at 949-470-3079.
Do I need flood insurance if I live near Aliso Creek or Oso Creek?
Federally backed mortgages on properties in mapped Special Flood Hazard Areas (Zones A, AE, AH, AO along the creek corridors) require flood insurance under federal law. Even outside the SFHA, the City recommends voluntary coverage because Mission Viejo's NFIP certification entitles residents to a discount on premiums, and homeowners insurance does not cover flood damage.
What does Mission Viejo require to build in a flood zone?
New construction and substantial improvements in mapped SFHAs must comply with FEMA minimum standards under 44 CFR 60.3 as adopted by City Ordinance 93-118: the lowest floor must be elevated to or above the Base Flood Elevation, structures must be properly anchored, and a stamped Elevation Certificate must be filed with the City before final inspection. New development in a regulatory floodway must show no rise in BFE.
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