Thursday, December 27, 2012

A Bit of River Perspective: The Eel River in Northern California

I was driving home from our Christmas visits with the family in central Oregon today. Since we were following Highway 101 through northern California's Redwood Country, we had a chance to look at the Eel River after several days of fairly intense rain. The picture above is a summertime view of the river from 2010 for sort of a baseline for comparing. As we drove along the river today I noticed it was filling the channel and inundating a fair number of trees. I wasn't thinking that it was flooding exactly, but it was full of sediment and moving fast. We stopped to grab a few pictures.
The river today was flowing at about 10,700 cubic feet per second. That would be flood stage on our own Tuolumne River, but was an unremarkable amount of water comparatively speaking. On Christmas Eve it was just over 20,000 cfs. We stopped at Miranda and had a bit of a shock. Some government entity had painted a river gauge on the bridge column to provide a bit of perspective...

You can click on the picture to see the writing better, but it essentially shows the depth of the water, which today was 14 feet deep. It's not considered to even be flooding until it reaches a depth of 33 feet, which would be a flow well in excess of 50,000 cubic feet per second. But a flood that size would be miniscule compared to what happened here in 1964; the water depth at Miranda was 46 feet, equivalent to 200,000 cubic feet per second. Downstream at Scotia where several forks of the river had combined, the water topped out at an unimaginable discharge of 752,000 cubic feet per second.
Needless to say, the damage was incredible, with entire towns being washed away. According to the Department of Water Resources, the North Coast rivers dumped 10.4 million acre-feet of water into the Pacific Ocean in six days. For comparison, Lake Powell on the Colorado River, a 186 mile long reservoir, holds 27 million acre feet. The average yearly flow of the Colorado is 14 million acre feet.

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