Flash flooding over McKinney Fire burn scar kills thousands of fish

Flash flooding caused by heavy rainfall over part of the burn scar from the McKinney Fire in northern California recently led to a massive fish die-off in tributaries of the Klamath River, the Karuk Tribe said in a statement last week.

Why it matters: The fish die-off is the latest sign of the devastation of the McKinney Fire. It has burned over 60,000 acres after starting on July 29, becoming California's largest fire this season. It has also killed at least four people, including fire officials and civilians, and destroyed several structures in multiple communities

• The wildfire is currently 40% contained and more than 3,200 fire personnel have been assigned to stopping its spread, according to InciWeb, an interagency website that tracks wildfires.

What they're saying: "Very large numbers of fish, of all species, are being observed in the vicinity of Happy Camp, [California], along the mainstream of the Klamath River," the Karuk Tribe said.

How it works: It takes less rainfall to cause flash flooding in areas burned by wildfires.

• As rainfall rushes downhill through a burn scar, it can cause major erosion and pick up large amount of debris — including ash, sand, soil, rocks and burned vegetation.
• If this debris flow washes into creeks or rivers, it can negatively alter the water's temperature and quality and throw off its pH level.
• This can affect fish and many other aquatic species that are sensitive to water pollution, especially if the contaminants reduce or deplete the level of dissolved oxygen in the water, according to the California Department of Fish & Wildlife.

Parts of the burn scar from the McKinney Fire received one to three inches of rainfall last Tuesday, according to InciWeb.

• The Karuk Tribe said that preliminary observations suggest that the fish likely died from debris flows caused by that rainfall event rushing into tributaries of the Klamath River.
• The thousands of dead fish then likely floated downstream where they gathered near Happy Camp and other communities along the mainstream of the Klamath River.
• The full extent of the die-off is currently unknown, as is whether the event will affect the fall migration of the Chinook salmon, Karuk Tribe said.

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