Winter rain and flooding in California has meant heavy erosion off hillsides and into the state’s waterways.
The state's rivers and streams are now chocolate-colored, heavy with dirt or sediment. While it might not look attractive, from an ecological standpoint it's good news, especially for native salmon.
“When you have high flows like this, where the water is more turbid, it provides cover for the fish and we expect the predation from predatory fish to go down and their survival to be higher,” says Howard Brown with NOAA's National Marine Fisheries Service.
High flows also carry fish across floodplains where they have more to eat and can flush out invasive species. Before dams were built, the state's rivers naturally carried more sediment.
The danger occurs when there’s too much erosion, all at once, or for prolonged periods.
Millions of salmon were moved from a fish hatchery at Oroville Dam for fear that too much erosion and turbid water from the damaged spillway would smother fish eggs.
“The very high levels of turbidity could actually clog the intake facilities at the hatchery and possibly shut off the water supply. So that was probably the driving concern,”says Brown.
Too much erosion, all at once, also leads to mudslides, debris flows and landslides.
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