Sources of flood hazards in Charleston include: the Stono, Ashley, Cooper, and Wando Rivers; Wappoo, Orangegrove, James Island, and Church Creek (riverine flooding); small (drainage of <100sq. acres) mapped and unmapped tidal creeks; and the Atlantic Ocean. Information on historic and past flooding events in the area is detailed in the Flood Insurance Study (FIS), which can be found at FEMA's Map Service Center.

The Charleston County Hazard Mitigation Plan identifies the following types of flood hazards: 

"Most of the flooding that occurs in the Charleston Region can be labeled as Coastal Flood, Flash Flood, and the general term Flood according to the National Oceanic and Atmospheric Administration (NOAA).

Coastal Flood: Flooding of coastal areas are due to the vertical rise above normal water level caused by strong, persistent onshore wind, high astronomical tide, and/or low atmospheric pressure, resulting in damage, erosion, flooding, fatalities, or injuries. Coastal areas are defined as those portions of coastal land zones (coastal county/parish) adjacent to the waters and bays of the oceans. Farther inland, the Storm Data preparer must determine when and where to encode a flood event as Flash Flood or Flood. 

Flash Flood: A rapid and extreme flow of high water into a normally dry area, or a rapid water level rise in a stream or creek above a predetermined flood level, beginning within six hours of the causative event (e.g., intense rainfall, dam failure, ice jam-related), on a widespread or localized basis. Ongoing flooding can intensify to flash flooding in cases where intense rainfall results in a rapid surge of rising flood waters. Flash floods typically recede quickly and do not exist for two or three consecutive days."  

The Charleston County Flood Insurance Rate Map (FIRM) provides expected Base Flood Elevations (BFEs) during the 1% annual chance flood event ("base flood"). 

A summary of flood zones relevant to Charleston County is provided below.

• Zones A and V are within the regulated Special Flood Hazard Area (SFHA). These are considered high hazard flood zones. 
• Zones X and D are outside of the Special Flood Hazard Area (SFHA).