The Historic West Coast Flooding of 1861–62

The greatest known recorded flooding, ever to impact the West Coast of the United States, occurred during the winter of 1861-1862. In fact, the extraordinary flood flows, on more than five major western rivers, remain the record peaks to this day. The flooding was caused by a series of Pacific mid-latitude cyclones and several extreme atmospheric rivers.

As the winter unfolds, the severe wet weather pattern shifts from north to the south, along the West Coast. The extreme rainfall initially strikes Oregon. The high water causes the flood of record on the Willamette River, with extensive devastation, wiping out several major towns along the river.  Communications, food and supplies were cut off for much of the winter in Oregon.The intense wet weather, then redevelops, moves south and stalls – pummeling Northern California with major flooding. The runoff fills California's Central Valley with a huge inland lake.  Sacramento is submerged into what was described as a "frontier Venice".  Flood damages eliminate a large part of the state's tax base. Finally the stormy pattern shifts into Southern California, producing major flooding. Most of lowland Los Angeles, Orange and San Diego counties are flooded under several feet of water for weeks. Meanwhile, north of the storm track, the Pacific Northwest is plunged into a deep arctic cold.  

The presenter researched limited weather data, historical accounts, maps and ship reports to reconstruct this series of storms and their effects along the West Coast. The extent and evolution of this series of flood events is unprecedented. Myths regarding the causes of this flood will be addressed, but the sheer magnitude is undisputable. This presentation demonstrates the nature of these consecutive major storms and subsequent flood impacts, while considering the consequences, if the weather pattern was repeated.