Storm Surge & Coastal Flooding
An abnormal rise of water generated by a storm, over and above the predicted astronomical tide. The deadliest hazard of any hurricane — and the reason coastal evacuation orders exist.
What is Storm Surge?
Storm surge is an abnormal rise of water generated by a storm, over and above the predicted astronomical tide. It's produced by the wind of a hurricane pushing seawater toward the shore — combined with the low atmospheric pressure at the storm's centre, which lets the sea bulge upward.
Surge isn't waves. Waves sit on top of the surge — the run-up. The surge itself is a wall of water that arrives as the storm approaches and stays as long as the storm sits over the coast. It can be several feet deep miles inland.
Most hurricane deaths are from drowning, not flying debris. In the Caribbean and southeast US, storm surge is the historic leading cause of hurricane fatalities — which is why coastal evacuation orders go out long before the wind arrives. If officials tell you to leave, leave.
Where Does Surge Strike?
Storm surge strikes coastal zones — anywhere the open sea can reach when pushed by hurricane-force winds. In Nevis, the most exposed coastal districts include:
- Charlestown waterfront — low-lying with high population density
- Pinney's Beach and the entire leeward coast tourism corridor
- Newcastle — including the airport low-ground
- Indian Castle, White Bay and the windward coast
- Any low-lying road, beach, or jetty along the Round Road
Storm surge is highest on the right-hand side of the storm's path (the side where wind blows onshore). The exact same hurricane can produce a 6-ft surge on one part of the coast and a 12-ft surge on another part — depending on which side you're on. Always evacuate when ordered; don't second-guess the forecast.
What to Do
The live ndmd.kn guidance is unambiguous: obey Coastal Zone Setbacks and evacuate from coastal areas on the approach of tropical storms. Here's the full preparedness picture:
Before
Know your zone. Plan the evacuation. Don't wait for the storm.
- Know whether your home is in a Coastal Zone Setback — if it is, plan to evacuate every storm
- Identify your nearest inland shelter and the route to get there
- Build an emergency kit — water, food, flashlight, battery radio, first aid
- Make a family communications plan and identify your meet-up point inland
- Move valuables, electronics and important documents to upper floors well before the storm
- Charge phones, laptops and battery banks; fill vehicles with fuel
- Protect property if time allows — board windows, secure outdoor items — but do not delay evacuation
During
If you're in a coastal evacuation zone — leave. There is no safe way to ride out major surge.
- If you live in a coastal evacuation zone, EVACUATE immediately when ordered — don't wait for the storm
- Do not try to wait out storm surge in a coastal home — water rises fast and traps people inside
- Stay tuned to NDMD, the Met Service and emergency officials for the latest surge forecast
- Stay away from beaches, coastal cliffs and waterfront — even before the storm arrives
- Do not drive on coastal roads once water has started rising — vehicles float
- If you become trapped on a coast, move to the highest floor of a sturdy building — never the attic
- Avoid contact with surge water — it carries debris, raw sewage and electrical hazards
After
Surge leaves contamination, debris and submerged hazards behind.
- Wait for officials to declare it safe before returning to coastal areas
- Stay away from standing water — surge leaves contamination behind
- Do not touch downed power lines, even if they look dead
- Beware of damaged structures, washed-out roads and submerged debris
- Check on coastal neighbours — surge often isolates them from emergency services
- Document property damage with photos before cleaning up (for insurance claims)
- Boil drinking water until officials confirm it is safe
Surge by Hurricane Category
Approximate open-coast surge ranges from the National Hurricane Center's Saffir-Simpson scale. Local geography, bay shape and coastline orientation can amplify these numbers considerably.
Category 1
Storm surge typically 4–5 ft above normal
Some flooding of coastal roads; minor pier damage.
Category 2
Storm surge typically 6–8 ft above normal
Coastal and low-lying escape routes flood 2–4 hours before arrival.
Category 3
Storm surge typically 9–12 ft above normal
Serious flooding inland up to 8 miles. Mass evacuations may be required.
Category 4
Storm surge typically 13–18 ft above normal
Major damage to lower floors of structures near the shore. Massive evacuations.
Category 5
Storm surge typically >18 ft above normal
Catastrophic damage to all coastal structures. Complete evacuation of coastal zones required.
Coastal Zone Setbacks
Coastal Zone Setbacks are the regulated buffer between the high-water line and where new construction is permitted. They exist precisely because of storm surge — the closer a building is to the water, the higher the chance it ends up in the surge zone.
NDMD's live site instruction is to obey Coastal Zone Setbacks. In practice this means:
- Check with the Physical Planning Department before any coastal construction
- Don't extend structures seaward of the setback line — even temporary ones
- Maintain dune vegetation and natural buffers — they reduce surge run-up
- If your property is inside the setback, plan to evacuate every storm
Words to Know
A 10-ft surge that arrives at low tide may only put 8 ft of water on land. The same 10-ft surge arriving at high tide produces 12 ft of storm tide — and that 4-ft difference covers thousands of additional homes. Forecasts account for this; trust the evacuation order.
Volunteer With Us
NDMD trains CERT volunteers in coastal evacuation support, post-surge damage assessment and shelter operations. Sign up online or pick up a form at the office.