What is First Flush?
Every year, as Ventura County transitions from the dry season to the rainy season, the first significant rainfall event—commonly called the "First Flush"—plays a critical role in our environment and waterways. While rain is essential for replenishing our water supplies and supporting natural ecosystems, the First Flush also brings unique challenges for water quality.
What Does the First Flush Sweep Up?
As rain begins to fall after a long dry period, it picks up a variety of pollutants that have built up on roads, sidewalks, and other surfaces. These pollutants are carried into storm drains and flow untreated into our creeks, rivers, and the ocean.
Common Pollutants
Litter / Trash
Plastic bottles, wrappers, cigarette butts, and other litter left on streets are swept into storm drains, contributing to ocean pollution.
Pet Waste
Rainwater washes bacteria and harmful pathogens from pet waste into waterways, posing risks to both wildlife and human health.
Pesticides
Chemical fertilizers and pesticides used on lawns and gardens can enter the water, harming aquatic life and disrupting ecosystems.
Household Hazardous Waste
Paints, cleaners, and other chemicals improperly disposed of can leach toxic substances into stormwater runoff.
Motor Oil and Vehicle Fluids
Leaks and spills from vehicles leave oil and other hazardous fluids on roads, which are then carried into the storm drain system by the First Flush.
Organic Debris
Lawn clippings, leaves, and other organic materials swept into storm drains decompose in waterways, reducing oxygen levels and threatening aquatic organisms.