“Atmospheric River” Produces Little Run Off

December 16, 2016

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Once saturated, scorched slopes like these, can produce dangerous debris flows. It just has to rain hard enough and long enough.

The atmospheric river type storm that swept through the Santa Lucia Mountains yesterday produced close to the advertised 6 inches of rain at the wettest Coast Ridge spots, but produced relatively little run off and no serious debris flow problems.

While slides predictably closed Highway One on the South Coast (it will probably reopen later this afternoon), the larger streams pretty much shrugged the event off.

The Big Sur River peaked at over 1,000 cfs last night, but its channel can accommodate many times that much water without difficulty. For comparison, during the storms following the Marble Cone Fire, in January 1978, the Big Sur River reached a record 10,700 cfs.

The Nacimiento River, whose watershed did not burn, reached the highest flow of any Santa Lucia stream early this morning, with around 2,500 cfs. That is a relative trickle for a stream that has produced flows exceeding 50,000 cfs during extreme rain events. No water has, so far, even reached the bone dry San Antonio River gauge.

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