The seller and his agent have to disclose the fact that the property for sale is in a Special Flood Hazard Area (SFHA).
What impact does a Flood Hazard Area Has on the buyer?
Federally backed up loans require you to carry Flood Insurance. Many lenders will also include such a requirement since they have to protect their investment.
Finding the Flood Zone for your Home
The FEMA has a website with flood information and search capabilities. Most of the US has been mapped in regard to possibilities of floods.
In the Sacramento area, areas that are the most at risk are the Rancho Cordova and Gold River area between Folsom Boulevard and the American River. Further down the river, the Cordova Meadows are affected. The parks around are expected to flood first, but then the meadows and other lots around that area are also at risk. We also have streams that can flood. An area where you have a dip is round Northtop Avenue which is considered to be a Zone AE (1% chance of getting a floor every year.) There are other areas North of the river that are mark Zone AE. All of which are close to a large stream. For example the stream going through Antelope can produce floods, although most homes are not in the zone.
(Ref. CAL. GOV. 8589.3)