Understanding Storm Surge
Storm surge causes more hurricane deaths than any other hazard. Here's what you need to know:
What is Storm Surge?
Definition: Abnormal rise in seawater level caused by a storm's winds pushing water onshore.
NOT:
- Regular waves
- Tide (though they combine)
- Tsunami
What Makes It Deadly:
- Speed: Can rise 10-15 feet in minutes
- Force: 1 cubic yard of water = 1,700 pounds
- Debris: Carries cars, buildings, anything
- Extent: Can penetrate miles inland
Factors That Affect Surge Height:
1. Wind Speed
- Stronger winds = higher surge
- Exponential, not linear relationship
- Cat 4 surge is NOT double Cat 2
2. Storm Size
- Larger storms push more water
- A large Cat 2 can have worse surge than small Cat 4
3. Forward Speed
- Slower storms = more time to pile up water
- Fast storms can catch people off guard
4. Angle of Approach
- Perpendicular to coast = worst surge
- Parallel tracks = less surge
5. Ocean Floor Shape
- Shallow, gradual slope = higher surge
- Deep water near shore = less surge
- Bays and inlets funnel water higher
6. Coastline Shape
- Concave shores trap water
- Barrier islands offer some protection
- Estuaries amplify surge
Storm Surge vs Storm Tide:
- Storm Surge: Rise due to the storm alone
- Storm Tide: Surge + normal astronomical tide
- High tide + surge = catastrophic combination
Surge by Category (General Guide):
- Cat 1: 4-5 feet
- Cat 2: 6-8 feet
- Cat 3: 9-12 feet
- Cat 4: 13-18 feet
- Cat 5: 18+ feet
Remember: These are rough estimates - actual surge depends on all factors above!
Why It's So Dangerous:
- Drowning: #1 cause of hurricane deaths
- Destruction: Can destroy any building
- Speed: Too fast to outrun
- Contamination: Mixes with sewage, chemicals
- Erosion: Permanently changes coastline
Your Action Plan:
KNOW YOUR ZONE:
- Check local evacuation zones
- Know your elevation above sea level
- Understand your surge risk
NEVER STAY if you're in:
- Zone A or B evacuation areas
- Mobile homes near coast
- Any flood-prone area
SURGE KILLS - HIDE FROM WIND, RUN FROM WATER
Common Fatal Mistakes:
- L "I survived the last one"
- L "My house is strong"
- L "I'm a good swimmer"
- L "It's only a Category 1"
- "I'm in a surge zone, I'm leaving"