Stormwater Management: Los Angeles vs Topanga
How do stormwater management rules compare between Los Angeles, CA and Topanga, CA?
Topanga has fewer restrictions than Los Angeles.
Los Angeles, CA
Los Angeles County
LAMC 64.72 (LID Ordinance, Ord. 183833) requires new development to manage stormwater runoff on-site through infiltration, bioretention, or capture systems. Priority projects must meet MS4 permit standards using the Development BMP Handbook. Projects disturbing 1+ acres need a state SWPPP. Grading permits are conditioned on stormwater compliance and a recorded covenant.
View full Los Angeles rules →Topanga, CA
Los Angeles County
Unincorporated LA County falls under the LA County MS4 NPDES permit. The LACFCD operates one of the largest flood protection systems in the world, including 14 dams and 80,000+ catch basins. Low Impact Development standards apply to new construction. The district captures and infiltrates 270,000+ acre-feet annually.
View full Topanga rules →Key Facts Comparison
| Fact | Los Angeles | Topanga |
|---|---|---|
| Code Section | LAMC 64.72 (LID Ordinance) | - |
| Requirement | On-site stormwater management | - |
| Hierarchy | Infiltration > bioretention > treatment | - |
| 1+ Acre Sites | State SWPPP required | - |
| Covenant | Recorded BMP maintenance agreement | - |
| MS4 Permit | - | LA County NPDES |
| LID Required | - | For new development |
| LACFCD | - | 14 dams, 80,000+ catch basins |
| Annual Capture | - | 270,000+ acre-feet infiltrated |
Highlighted rows indicate differences between cities.
Los Angeles FAQ
Do I need a stormwater plan for my project?
Generally required for new construction and major renovations that increase impervious surface area. Small residential projects may be exempt.
What is an illicit discharge?
Any non-stormwater substance entering the storm drain system, including paint, oil, chemicals, or sediment. Report violations to Los Angeles public works.
Topanga FAQ
What can go into storm drains in LA County?
Only stormwater. Illicit discharge of chemicals, wash water, paint, oil, or other pollutants is prohibited under Title 12 and the MS4 permit. Storm drains flow directly to rivers, ocean, and groundwater.
What are LID standards?
Low Impact Development standards require new development to capture and treat stormwater on-site through features like bioswales, permeable paving, cisterns, or rain gardens. They apply to new construction and major renovations.
How do I report illegal dumping into storm drains?
Call the LA County illegal dumping hotline at (888) 846-0800. For active spills or hazardous discharges, call 911 or the LA County Fire Department hazmat line.
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