The flood insurance will (based on my understanding) by a separate policy from your homeowners and is based on the degree of zone the home is in.
Check here for a description of the ratings and an interactive map at the bottom to see your area. Click on flood zones.
Charleston Flood Zone Descriptions
This map lays out the areas that would be flooded based on a direct hit to Charleston and also based on the storm category. It says:
Using a well-named computer model called
SLOSH, which stands for
Sea, Lake and Overland Surges from Hurricanes.
A
SLOSH map is generated to show what a hypothetical direct hit on Charleston would be like, and provides an intriguing snapshot of how the city might fare in certain hurricane scenarios.
This SLOSH map has calculations for a hurricane with an eye coming in south of Kiawah Island. This reflects more of a worst-case scenario for the city because surges are higher in a storm's northeastern quadrant.
In a Category 1 storm, a
surge of 7 to 10 feet would have a relatively minor effect on the area. Floodwaters would fill the area's marshes and low-lying areas on the peninsula and the sea islands. But parts of the Isle of Palms and other barrier islands would still remain above water.
That changes dramatically in a Category 2 storm with a
surge of 12 feet. In this scenario, the barrier islands all but disappear and most of downtown Charleston and James Island flood.
In Mount Pleasant, the only dry ground would be along Johnnie Dodds Boulevard, which is built on an ancient sand ridge. In this Category 2 scenario, floodwaters would begin to march into North Charleston toward Park Circle. And for the first time since it was developed, most of Daniel Island would temporarily lose its island status and become a seabed.
In Category 3 surge,
most of West Ashley goes under water, along with a few specks of downtown Charleston.
In a Category 4 scenario, a
15- to 20-foot surge inundates much of Johns Island, while floodwaters on the Charleston Neck are neck deep.
A Category 5 scenario?
Some parts of Charleston would be under more water than the low areas of New Orleans after Katrina.
Forecasters caution that SLOSH maps aren't perfect. They say the calculations have a 20 percent margin of error, and they also don't take into account tides, which could add or subtract a few feet of surge depending on a hurricane's timing.