During Hurricane Sandy, the most recent storm, flooding occurred in places that never flooded before. That includes north of Atlantic Avenue on Guy Lombardo Avenue. Again, some basements flooded and some did not.
Why do you ask? Are you considering buying or renting a home in South Freeport? If you want to talk to me about homes in Freeport (or anywhere on the south shore of Nassau County) please give me a call at 516-410-3000 and I will be happy to tell you anything you want to know about a neighborhood. (By the way, as a Buyer's Agent I represent YOU, not the seller, so I can provide a lot of information that the seller's agent cannot.)
Please note that flood insurance doesn't cover contents in a basement. Traditionally only the boilder and HW heater would be covered. You can check your policy to see if there's coverage for your washer and dryer. During Sandy my circuit breaker boxes were under the water so they would be covered for this damage as well on my policy.
Be sure to contact http://www.disasterassist.gov for more help.