There's no need to go back thousands of years, nor to consult geological records, to know that California's flood season can be bad: https://en.wikipedia.org/w

There's no need to go back thousands of years, nor to consult geological records, to know that California's flood season can be bad: https://en.wikipedia.org/wiki/Great_Flood_of_1862 https://en.wikipedia.org/wiki/Great_Flood_of_1862 (Summary: 1/4 of all taxable property in the state was destroyed; 1% of the state's population died; things were also pretty grim in all the surrounding states and Mexico.)