I'm not sure but if you look at maps of both floods it seems that weather pattern in 1964 was a lot further north than the 1862 flood. Also, the wiki article fo

I'm not sure but if you look at maps of both floods it seems that weather pattern in 1964 was a lot further north than the 1862 flood. Also, the wiki article for 1862 says that that was an El Nino year.