Surge & Flooding
Official SLOSH surge planning map, category reference, and live NWS coastal flood products for the district.
Planning map — Category 1–5 surge (near worst-case)
NOT CONNECTEDCharleston County SLOSH · NWS SLOSH MOM
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District center — Cat 4 surge
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Surge raster
10 m grid
NHC Storm Surge Hazard Maps: near worst-case flooding for each hurricane category (pick 1–5). Actual surge depends on track, size, forward speed and tide — not a forecast for any specific storm. Tap the map for the water depth at a spot.
Live mode — Coastal Flood Event Viewer, ZIP 29455
Source: NWS Charleston (weather.gov) · live, provided by NWS
Category reference — winds & surge
Saffir–Simpson scale · SJFD planning schematic
| Cat | Sustained winds | Surge (planning) |
|---|---|---|
| 1 | 74–95 mph | 4–5 ft |
| 2 | 96–110 mph | 9–12 ftmatches Cat 3 in this plan; older NHC tables listed 6–8 ft |
| 3 | 111–129 mph | 9–12 ft |
| 4 | 130–156 mph | 13–18 ft |
| 5 | 157+ mph | >18 ft (mapped at 18–22 ft) |
The map above shows the official NHC scenario for each category. Since 2010 the Saffir–Simpson scale describes wind alone — surge depends on track, size, speed and tide as well.
On these islands
SJFD planning schematic (30 Sep 2026)
- Kiawah and Seabrook's Atlantic-facing dune ridge takes the worst wave action on top of surge.
- Inlets — Stono, Captain Sam's, Bohicket, North Edisto — funnel surge into the creeks behind the islands. Captain Sam's shifts the Kiawah/Seabrook shoreline most.
- Tidal marsh and creeks (Kiawah River, Bohicket Creek, Stono and Wadmalaw Rivers) flood first from the back side. The causeways to Kiawah, Seabrook and Wadmalaw cross this marsh.
- Johns Island's interior stays dry longer because surge tapers inland — but its flat ground drains slowly, so heavy rain can flood it independently of surge.
- Surge is highest to the right of the eye; a storm tracking southwest puts these islands in the strongest quadrant. A ~5 ft tide range means landfall near high tide adds to the surge.
Basis & caveats
Charleston County Resilience · SCEMD · hurricane.sc
- Surge raster: the official Charleston County SLOSH Category 4 inundation service (NWS SLOSH MOM, near worst-case per category).
- Evacuation zones: Charleston County evacuation zones (Seabrook and Kiawah in Zone A; Johns Island in Zones B and C) and hurricane.sc. See the Evacuation page.
- For evacuation or operational decisions, follow official NHC/NWS and Charleston County guidance — this page is a planning aid, not a decision.