Flood Zones: Altadena vs Downey
How do flood zones rules compare between Altadena, CA and Downey, CA?
Altadena and Downey have similar restriction levels.
Altadena, CA
Los Angeles County
Most of Altadena is in FEMA Flood Zone X (minimal hazard), but the area along Eaton Wash, the Arroyo Seco tributaries, and post-Eaton Fire burn-scar areas have heightened flood and debris-flow risk. LA County Code Ch. 22.142 (Floodplain Management) applies in mapped Special Flood Hazard Areas.
View full Altadena rules →Downey, CA
Los Angeles County
Portions of Downey fall within FEMA-designated flood zones, primarily along the Los Angeles River and Rio Hondo channels. The city participates in the National Flood Insurance Program and enforces floodplain development standards.
View full Downey rules →Key Facts Comparison
| Fact | Altadena | Downey |
|---|---|---|
| Most of Altadena | Zone X (minimal hazard) | - |
| Eaton Wash Adjacent | Zone A / AE possible | - |
| Code Section | LA County Code Ch. 22.142 | - |
| BFE+1 Required | In SFHA | - |
| Post-Eaton Fire | Elevated debris-flow risk | - |
| NFIP Participant | - | Yes |
| Flood Areas | - | LA River, Rio Hondo corridors |
| Building Code | - | CA Building Code floodplain provisions |
| Flood Maps | - | FEMA Flood Map Service Center |
| Public Works | - | (562) 904-7110 |
Highlighted rows indicate differences between cities.
Altadena FAQ
Is Altadena in a flood zone?
Most of Altadena is in FEMA Zone X (minimal hazard), but areas along Eaton Wash and the foothill channels can be in Zone A/AE. Check the FEMA Map Service Center for your specific parcel.
Did the Eaton Fire affect flood risk?
Yes — post-fire burn scar areas above Altadena have elevated debris-flow and flash-flood risk during winter storms. USGS and NWS issue post-fire debris-flow advisories.
Downey FAQ
Is my Downey property in a flood zone?
Check FEMA's Flood Map Service Center at msc.fema.gov for your property's flood zone designation. Properties near the LA River or Rio Hondo may be in Special Flood Hazard Areas.
Do I need flood insurance in Downey?
Properties in FEMA-designated Special Flood Hazard Areas with federally backed mortgages are required to carry flood insurance.
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