Surge impacts aren’t necessarily tied to the power of a storm. Category 5 Andrew, for instance, was a small, fast-moving storm with surge that peaked at 16.5 feet near the Deering Estate but affected a relatively narrow section of the South Miami-Dade coast. Sandy dropped near Cat 1 strength when it neared the Northeast but the massive, slow-moving storm drove the sea deep inland.
“It depends on a whole bunch of variables,’’ Brinkley said. “The size of the storm, the forward speed, the angle of approach to land, the timing with high tide and low tide, all of these factors come into play and can have big implications.’’
Though the evacuation zones have expanded, Sommerhoff believes that improved NHC predictions will help reduce unnecessary evacuations by helping the county pinpoint only the pockets most likely threatened. Depending on the storm, only small sections of inland zones might be evacuated, he said, with the county issuing the street boundaries of the areas considered at risk.
In the wake of the brutal 2004 and 2005 hurricane seasons, Florida lawmakers tapped $29 million in federal funding to pay for a statewide evacuation study that included aerial surveys using laser technology that provides the most precise measures of elevation. Those maps, and NHC surge models, were used to develop the new zones for Miami-Dade, which had not updated its map in about 10 years.
Miami-Dade worked with other agencies, including the South Florida Water Management District, which runs the regional flood-control system, to develop a final map, Sommerhoff said. He said he wasn’t sure if other counties would do similar updates but said he believed Broward had examined its maps and did not plan changes. Broward emergency managers and the Florida Division of Emergency Management did not return calls.
The surge zones don’t affect maps that the Federal Emergency Management Agency use to set national flood insurance policy rates.
Though Miami-Dade began working on the update early last year, Hurricane Sandy proved a powerful reminder that water, rather than wind, is the biggest threat.
Sommerhoff recalls watching one woman in New Jersey on TV wondering how so much water was in her home when she lived two miles from the beach.
“Here,’’ he said, “it could be 10 miles from the coast.’’