How do hurricanes cause damage to coastal infrastructure?

Oak Island, North Carolina, was hit hard by Hurricane Floyd in 1999. (Photograph by the author. More about the photograph)

A fully formed hurricane carries three major threats to coastal development: low atmospheric pressure, high surface winds, and heavy rainfall. These threats are realized in different ways.

• Low central pressure becomes a threat when ocean water bulges up under it and forms a storm surge when the hurricane comes ashore.
• High surface winds can damage property directly, but create an even more destructive force by creating high waves on the ocean surface.
• Heavy rainfalls add to coastal damage by creating flooding and by increasing both erosion and pollutant input as they run off the land.

We will see all three damaging effects on this field trip. The general result of all three major threats is to flatten and broaden the beach.

A flat beach dissipates the turbulent energy of waves more effectively than a steep beach because it provides a longer distance over which the turbulent energy of waves can be drained away by friction or converted to heat. The fact that high energy waves broaden and flatten beaches, thereby making them better able to dissipate energy from the waves themselves, is an example of an environmental feedback loop that all beachgoers should be aware of, and that all homebuyers should evaluate carefully before they purchase beachfront property.

The photograph on this page shows what happened on Oak Island when Hurricane Floyd flattened and broadened the beach in September 1999. The first row of beachfront houses were destroyed, as was the primary dune and the road that once ran behind it. There are ways to minimize this type of damage. Some of them will be described in this field trip.

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