https://en.wikipedia.org/wiki/Christmas_flood_of_1964] The Christmas flood of 1964 was a major flood in the Pacific Northwest and some of Northern California between December 18, 1964, and January 7, 1965, spanning the Christmas holiday.[1] Considered a 100-year flood,[2] it was the worst flood in recorded history on nearly every major stream and river in coastal Northern California and one of the worst to affect the Willamette River in Oregon. . . . California Governor Pat Brown was quoted as saying that a flood of similar proportions could "happen only once in 1,000 years," and it was often referred to later as the Thousand Year Flood.[1] The flood killed 19 people, heavily damaged or completely devastated at least 10 towns, destroyed all or portions of more than 20 major highway and county bridges, carried away millions of board feet of lumber and logs from mill sites, devastated thousands of acres of agricultural land, killed 4,000 head of livestock, and
caused $100 million in damage in Humboldt County, California, alone.[6][7]
An atypical cold spell began in Oregon on December 13, 1964, that froze the soil, and it was followed by unusually heavy snow.[3][8] Subsequently, a Pineapple Express storm brought persistent, heavy, warm rain.[3][8] The temperature increased by 30 to 40 °F (17 to 22 °C).
This melted the snow, but left the soil frozen and impermeable.[8] Some places received the equivalent of a year's rain in just a few days.
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Starting on December 21, intense downpours all across Northern California caused numerous streams to flood, many to record-breaking levels. California Governor Brown declared 34 counties in the region disaster areas.[1][7]
Together, Del Norte, Humboldt, Mendocino, Siskiyou, Trinity, and Sonoma counties sustained more damage than the other 28 counties combined.[7] Twenty-six U.S. Geological Survey (USGS) stream gauges were destroyed.[7]
North Coast
The Eel, Smith, Klamath, Trinity, Salmon, and Mad rivers, as well as other rivers and large streams, all went well beyond flood stage and peaked nearly simultaneously around December 21 and 22, breaking previous records (notably those set in the "hundred year" flood of 1955 in most cases).[1][7] Sixteen state highway bridges were destroyed in California's 1st congressional district, most of them on Highway 101, and another 10 county bridges were destroyed in Humboldt County.[7] The flood devastated the tracks and multiple stream and river crossings of the Northwestern Pacific Railroad, the region's only major railroad, and related spur lines.
Many communities of Del Norte and Humboldt counties suffered massive power outages and were left isolated (or completely cut off from the rest of the state for a period), including the region's larger populated areas around Humboldt Bay, such as Eureka and Arcata, despite the fact that those cities were located on higher ground and not in the path of raging rivers. Unfortunate riverside communities like Klamath, Orleans, Myers Flat, Weott, South Fork, Shively, Pepperwood, Stafford, and Ti-Bar were completely destroyed by flood waters; some of them were never rebuilt and none regained their former status. Metropolitan, Rio Dell, and Scotia were significantly damaged.[7] Crescent City, still recovering from the tsunami created by the 1964 Alaska earthquake only nine months earlier, also suffered from the floods.[7]
Over 22 inches (550 mm) of rain fell on the Eel River basin in a span of two days. By December 23, 752,000 cubic feet per second (21,300 m3/s) of water rushed down the Eel River at Scotia (still upstream from the confluence of the Van Duzen River),[6] 200,000 cubic feet per second (5,660 m3/s) more than the 1955 flood, and
more than the average discharge of the entire Mississippi River basin.[9] Just under 200,000 cubic feet per second (5,660 m3/s) of water flowed down the South Fork Eel River alone, causing severe damage along its entire length.[6] Every single stream gauge on the Eel River was destroyed.[7] The flood crest at Miranda was 46 feet (14 m). Signs were later placed on top of tall poles to mark the unusual height of the water.[10]
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The Klamath River reached flows of 557,000 cubic feet per second (15,800 m3/s),[12]
submerging the town of Klamath under 15 feet (4.6 m) of water.[7]
The Trinity River, one of the Klamath's largest tributaries, also flooded and wrought destruction along its length. The Trinity, however, did not break the 1955 flood's records because of the newly constructed Trinity Dam, which stored 372,200 acre feet (459,100,000 m3) of runoff from the storm.[7] Nonetheless, an impressive 231,000 cubic feet per second (6,540 m3/s) of water rushed down the river at Hoopa.[13]