Beyond the Flood Zone: Storm Surge Multiplies Coastal Vulnerabilities

By | April 30, 2010

“Homeowners can mitigate against wind damage, but they’re powerless, really, to do anything against storm surge,” says one researcher whose job it is to develop ways to determine the vulnerability of homes and other properties not only to storm surge, but wildfires, sinkholes, earthquakes and other natural perils.

Dr. Howard Botts, vice president and director of development for First American Spatial Solutions (FASS), says a recent report and model developed by his company are able to demonstrate how destructive, both physically and financially, storm surge can be.

Storm surge is “such a large scale phenomenon that doesn’t really respect construction and other kinds of things,” Botts said. “If you’re in a storm surge zone, you’re likely to be impacted by it.”

Until Hurricane Katrina in 2005, however, the impact of storm surge on the overall property losses caused by hurricanes was generally not in the forefront of concern to most residential property insurance companies. After all, storm surge was a flood loss not covered by the traditional homeowners insurance policy.

Katrina and the lawsuits that followed changed that mindset.

Insurers, and indeed the world, saw first hand the amount of damage storm surge could produce. Just three years later, Hurricane Ike blasted ashore near Galveston, Texas, with a massive storm surge that helped it become the third most costly U.S. hurricane on record, largely due to the surge.

A member of the First American Corp. family of companies, FASS has access to information on around 90 percent of all the private properties in the United States, or at least 124 million separate addresses. The group has used that information to develop a model to analyze storm surge exposure at the individual property level.

The 2010 First American Storm Surge Report released in late March illustrates the exposure of single residential structures to storm surge in 13 key geographic areas. The numbers are massive. The storm surge exposure to Miami alone in the event of a Category 5 hurricane $53.6 billion, according to the report.

Flood Coverage or Not?

Insurance agents throughout the United States, and especially those whose customers own properties near the nation’s coastlines, are painfully aware that only a fraction of residential property owners that need the protection of flood insurance actually buy it. Even homeowners in areas that are high risk for flooding sometimes are reluctant to spend the extra money, although the coverage is far less expensive than traditional property insurance.

Botts said the information provided by the storm surge hazard model could be a useful tool for agents and insurance companies to use to educate insureds about the danger of storm surge in vulnerable coastal areas — and in informing property owners of the need to buy flood insurance.

“What we do is we build large, hazard risk data sets, tax data sets, sales and use tax, premium tax for the insurance industry. And we combine these very granular risk-hazard or tax databases with a geocoder that we developed, which takes an address and can get you right down to, literally, the rooftop,” Botts said.

What this means for insurers, and agents, is that they can visibly show owners of properties along and near the hurricane prone coastlines just what the impact of storm surge from a Cat 1 or Cat 5 hurricane, or any size storm in between, would be on a particular insured’s property.

For example, storm surge report released in March was designed “to look at 13 major residential property markets in the Gulf and Atlantic coastal region and understand, at a property-by-property level, which of these properties were in a storm surge potential area or would be exposed to storm surge,” Botts explained. Then property-by-property the dollar value of those single family homes — the buildings only, not the contents — in potentially affected areas was determined.

A Ton of Water

“Storm surge moves with the forward speed of the hurricane — typically 10–15 mph,” the report states. “One cubic yard of sea water weighs 1,728 pounds — almost a ton.”

Adding to the impact of rushing water, the trees, pieces of buildings and other debris that are typically caught up in the swirl act as a battering rams when they come into contact with a stationary object, such as another building.

Even areas that are not in direct path of a hurricane can be hugely impacted, as evidenced during Hurricane Ike, when its storm surge powered north up Galveston Bay, along the east side of Houston.

Botts says natural and man-made channels and barriers can add to the destructive possibilities.

“What’s going to facilitate inward movement? Creeks, bayous, drainage ditches,” he said, adding that un-raised highways and railroad rights-of-way can also serve that purpose. Meanwhile, natural and man-made barriers, such as hills, levees, even mounds of earth can keep the surge from flowing out of inland areas.

“We spend an enormous amount of time looking at what happens once that water gets onshore, what are the likely areas of inundation,” Botts said.

Listen to Insurance Journal’s interview with Dr. Howard Botts online at

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