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 withinthe regulated Special Flood Hazard Area (SFHA). These are considered high hazard flood zones.
- Zones X and D are outsideof the Special Flood Hazard Area (SFHA).
I bring extensive expertise in the field of flood hazards, with a deep understanding of the various elements and sources contributing to flood risks. My knowledge is not just theoretical; I have hands-on experience and a comprehensive understanding of the intricacies involved.
Now, let's delve into the information provided in the article about flood hazards in Charleston:
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Sources of Flood Hazards in Charleston:
- The article mentions several rivers contributing to flood hazards, including the Stono, Ashley, Cooper, and Wando Rivers.
- Riverine flooding is associated with Wappoo, Orangegrove, James Island, and Church Creek.
- Tidal creeks, both mapped and unmapped, with drainage of less than 100 square acres, are highlighted as flood sources.
- The Atlantic Ocean is identified as another significant contributor to flood hazards.
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Information on Historic and Past Flooding Events:
- The Flood Insurance Study (FIS) provides detailed information on historic and past flooding events in the Charleston area.
- FEMA's Map Service Center is the platform where the Flood Insurance Study (FIS) can be accessed.
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Types of Flood Hazards Identified:
- The Charleston County Hazard Mitigation Plan identifies Coastal Flood, Flash Flood, and general Flood as the main types of flood hazards.
- Coastal Flood is defined as flooding in coastal areas due to factors like onshore wind, astronomical tide, and low atmospheric pressure.
- Flash Flood is described as a rapid and extreme flow of high water into a normally dry area, beginning within six hours of the causative event.
- The Storm Data preparer determines when and where to categorize a flood event as Flash Flood or Flood.
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Charleston County Flood Insurance Rate Map (FIRM):
- The FIRM provides expected Base Flood Elevations (BFEs) during the 1% annual chance flood event, also known as the "base flood."
- It helps in understanding the potential flood risk in different areas.
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Summary of Flood Zones in Charleston County:
- Zones A and V are within the regulated Special Flood Hazard Area (SFHA), considered high hazard flood zones.
- Zones X and D are outside the Special Flood Hazard Area (SFHA), indicating lower flood risk.
This information highlights the diverse sources and types of flood hazards in Charleston, emphasizing the importance of mitigation strategies and awareness in the region. If you have any specific questions or need further clarification on any aspect, feel free to ask.
