Christmas flood of 1964

Christmas flood of 1964

An aerial view of the flood, showing Willamette Falls and Oregon City
Date	20 days December 18, 1964 (1964-12-18)–January 7, 1965 (1965-01-07)
Location	California, Oregon, and Washington states

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. Considered a 100-year flood, 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. It also affected parts of southwest Washington, Idaho, and Nevada. In Oregon, 17 or 18 people died as a result of the disaster, and it caused hundreds of millions of dollars in damage. The flooding on the Willamette covered 152,789 acres (61,831.5 ha). The National Weather Service rated the flood as the fifth most destructive weather event in Oregon in the 20th century. 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. 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.

An atypical cold spell began in Oregon on December 13, 1964, that froze the soil, and it was followed by unusually heavy snow. Subsequently, a Pineapple Express storm brought persistent, heavy, warm rain. The temperature increased by 30 to 40 °F (17 to 22 °C). This melted the snow, but left the soil frozen and impermeable. Some places received the equivalent of a year's rain in just a few days. Albany received 13 inches (330 mm) of rain in December, almost double its average December rainfall of 7 inches (200 mm).Detroit recorded an extra 18 inches (460 mm) of rain, and at Crater Lake, where the average normal December rainfall is 12 inches (300 mm), there was over 38 inches (970 mm) of rain. As rivers and streams overflowed and the soil became saturated, mudslides occurred, roads closed, and reservoirs overflowed. Many towns were isolated. By the end of the flood, every river in Oregon was above flood stage, and more than 30 major bridges were impassable.