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gb
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PostSat Dec 01, 2018 2:18 am 
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monorail wrote:
gb wrote:
There is an old 1961 report in pdf form that I read a couple of days ago that describes all of the major floods on the Skagit (to 1961).

That sounds interesting; do you happen to have a link?

I wonder if the 1810-1820 flood involved some kind of huge glacial outburst.

https://pubs.usgs.gov/wsp/1527/report.pdf

USGS revisited Stewart's work in 2008, revising by analysis and modeling some of the historic Skagit floods.
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monorail
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PostSat Dec 01, 2018 5:44 pm 
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Thanks, GB, that is quite interesting. I came across another pdf concerning Skagit flood history; this one is more anecdotal, relying on contemporary accounts: http://www.skagitriverhistory.com/PDFs/HISTORICAL%20FLOODS--%20SKAGIT%20RIVER.pdf

This account from the late 1800s seems to pertain to the c.1815 flood:

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Our fellow townsman, Mr. H.L. Devin, was some years ago engaged in surveying in the upper valley in the vicinity of Baker Lake. Being detained over night in an Indian camp, he was told the history of a great flood. They said that about 60 years ago a great slide had choked up the narrow outlet of the Baker Valley and that the water accumulated in the basin thus formed until the whole valley was an immense lake, full 80 feet deep. By this time the imprisoned waters had burst through the dam and in a few hours this great volume of water was precipitated into the Skagit flooding the whole valley. The water marks still plainly visible high up the sides of the Baker Valley and the great variation in those upon the trees as you come down the Skagit would indicate that this was the real cause of that terrible disaster.

But apparently USGS does not believe this occurred. And it's hard to see how it would have caused flooding in the Diablo area (which was affected by the 1815 flood). On the other hand, extreme weather could have caused multiple events around the same time, i.e. a huge general flood followed later by the Baker Valley landslide/flash flood.
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gb
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PostSun Dec 02, 2018 12:08 pm 
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monorail wrote:
Thanks, GB, that is quite interesting. I came across another pdf concerning Skagit flood history; this one is more anecdotal, relying on contemporary accounts: http://www.skagitriverhistory.com/PDFs/HISTORICAL%20FLOODS--%20SKAGIT%20RIVER.pdf

This account from the late 1800s seems to pertain to the c.1815 flood:

Quote:
Our fellow townsman, Mr. H.L. Devin, was some years ago engaged in surveying in the upper valley in the vicinity of Baker Lake. Being detained over night in an Indian camp, he was told the history of a great flood. They said that about 60 years ago a great slide had choked up the narrow outlet of the Baker Valley and that the water accumulated in the basin thus formed until the whole valley was an immense lake, full 80 feet deep. By this time the imprisoned waters had burst through the dam and in a few hours this great volume of water was precipitated into the Skagit flooding the whole valley. The water marks still plainly visible high up the sides of the Baker Valley and the great variation in those upon the trees as you come down the Skagit would indicate that this was the real cause of that terrible disaster.

But apparently USGS does not believe this occurred. And it's hard to see how it would have caused flooding in the Diablo area (which was affected by the 1815 flood). On the other hand, extreme weather could have caused multiple events around the same time, i.e. a huge general flood followed later by the Baker Valley landslide/flash flood.

I read this entire article and found it interesting. Subsequent to floods in 1951, other great floods occurred in the Northwest in 1990, 1995, 2003 (also certainly in 2007). I found a number of reports including a government report in pdf form for the floods of 1990 which included precipitation figures from several stations https://pubs.usgs.gov/of/1993/0631/report.pdf. In some locations 1990's flood was described as a 100 year event. Additionally I found Larry Kunzler's article and comments regarding floods including 2003 that gave precipitation records and in which Kunzler stated the 2003 flood period was Washington's wettest. Somewhere it was also stated that the maximum six hour rainfall rate was .5" per hour. On November 26th, 2018 Buckhorn's rainfall nearly matched that rate with 2.5" of rain in six hours: https://www.wrh.noaa.gov/mesowest/getobext.php?wfo=sew&sid=BKHW1&num=168&raw=0&dbn=m

Had the rain continued longer than the 36 hours it did, it seems highly likely that we would have had major floods.

The 1990 flood was Washington's worst but it appears 2003 exceeded that and 2007 probably blew it away particularly in the South Cascades.
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gb
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PostSun Dec 02, 2018 12:43 pm 
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A very disconcerting trend note the increase in 100 year floods in the last three decades:

https://pubs.usgs.gov/fs/2011/3146/pdf/fs20113146.pdf
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