Jim did give you a good answer...I think that if you are not in a flood zone, and flood insurance is not actually mandated by your lender, there is a 30-day waiting period for the flood insurance to take effect.
If you are looking to live in Midtown, Land Park, or East Sac (all fantastic choices, by the way!), flood insurance is a good idea, although in many neighborhoods it will not be required by your lender. FYI, several homes in those areas have basements, and flood insurance will only cover structural-type damage to a basement that may be caused in a flood...if you have a finished basement, you will be out of luck when it comes to replacing any "finishes" (carpet, drywall, etc).
You are correct - water flows where it wants to...and we do not have to have a Hurricane Katrina-like disaster here for homes to flood. When I was a kid living in Citrus Heights (not even close to a flood zone), there was a storm that flooded our street. Luckily our house sat up really high, and when my parents landscaped they installed lots of additional drainage measures. A neighbor across the street who sat lower and who had bad drainage flooded...just a couple of inches of water destroyed lots of belongings and did some pretty severe damage to that house. You can obtain basic flood insurance for about a dollar a day...definitely a small price to pay for that kind of security.
Looking at your other questions, you certainly seem to be doing your research! It is good to have the whole picture before you start your search! Good luck to you with your house hunt.
That will determine the Property's risk level. With the risk level in mind you can then navigate to: http://www.floodsmart.gov/floodsmart/pages/premiumest.jsp
Which gives you a high estimate. The city of Sacramento is has a community rating system discount from the high estimate by 20%.
I ran a sample high risk house in Land Park (near Sutterville School Park) through the estimator. The estimate came to $1969.60 for $250,000 of building coverage and $100,000 of contents coverage.
Important: Your individual situation may differ from the conditions used for this estimate. A flood insurance agent can provide you with an accurate quote for your specific property and contents.
Last year I lent $40 million to Katrina flood and other disaster victims. Many of them had inadequate flood insurance coverage or none at all. You are wise in your decision to obtain flood insurance even if you buy in a non SFHA zone (non Special Flood Hazard Zone such as X)
In my experience, the line between AR and X zones in central Sacramento is a little arbitrary, like the lines were not drawn by actual flood risk, but in part by political wrangling. Some things that seem like they should be in AR zone (Old Sac comes to mind) are in X zone. I've definitely seen water running through the streets of Sacramento, and it doesn't stop when it gets to that X line, it just keeps on flowing. So even if we aren't required to buy insurance, we are definitely going to.
A local insurance company should be able to give you a quote on AR, they will need information on the home you are planning to buy.
If you have not identified a home yet, let them know and give them your approximate parameters for purchase.
Best of luck