The report says that in December 1861, severe storms lashed the area for 45 days. So, something you could actually go to a library and read old newspaper articles on.

Well, I'm not holding my breath waiting for the whole Central Valley to flood in an ARkstorm, but large-scale localized flooding could do a lot of damage, especially if it occurred in the Sacremento area. The city (our capital) itself could be underwater. And since this region is where the water heading for southern California originates, if flooding threatened the water supply heading south, I have read elsewhere that the aqueduct would be shut down.

A similar set of outcomes exists if the next major earthquake causes the extensive levee system in the Sacramento River Delta area to break down, causing a different kind of flooding and shut down of the California aqueduct.