Storm Surge Becomes Sandy’s Loss Wildcard

The unique and historic nature of Hurricane Sandy’s storm surge component makes estimating pre-event insured losses a losing game since, according to catastrophe modeling experts.

“This is a very large storm system with multiple components,” says Steve Bowen, senior scientist, Aon Benfield Impact Forecasting. “Storm surge along the coast is one of the biggest threats.”

Storm surge alone could be a major loss provider, with surge levels from six to eleven feet possible in some costal areas in Sandy’s path, according to a Monday statement catastrophe modeling firm EQECAT. In addition, a combination of Sandy making landfall during a full moon could put storm surge destruction to even higher, firm stated.

“This is a very large system that will remain over multiple tide cycles,” Bowen says. “In addition, you have a large wind field that will take down trees. There could be significant insured loss with utility damage and infrastructure damage.”

The New York region is most at risk to storm surge loss with east-facing bays like Long Island Sound, Raritan Bay, and New York City Harbor experiencing near-record surge heights, according to modeling firm AIR Worldwide. The statement adds that flood walls in Manhattan are five feet above mean sea level, “indicating a good possibility that Sandy’s surge can inundate parts of the subway system.”
The problem is extrapolating expected insured losses in this storm is that meteorologists and modeling firms have not seen the possible storm surge levels that Hurricane Sandy in the past to base loss assumptions.

“The level of storm surge from the Delmarva Peninsula to New York City has never been seen before,” Bowen says. “Meteorologist were skeptical [of the models] at first, but the projections are much more certain. It’s such a unique set of circumstances.”

Inland flooding is also a danger, but a relatively dry ground prior to the the storm should limit damage. “The heaviest rains are expected on the south side of the storm. Fortunately, soil moisture and river levels are low to average over much of the region, which will moderate the possibility of catastrophic river flooding,” Dr. Tim Doggett, principal scientist at AIR in a statement. “This is in contrast to the heavily saturated soils at the time of Hurricane Irene’s arrival, which caused several billions of dollars of flood damage.”

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