Hurricane Isaac, packing high winds and heavy rain, left insured damage as high as $2 billion along the Gulf Coast last week, but spared New Orleans a repeat of the devastation Hurricane Katrina inflicted seven years ago.

As a Category 1 hurricane, Isaac made landfall in southeastern Louisiana, but its maximum sustained winds of 80 mph bypassed downtown New Orleans.

Nonetheless, almost eight inches of rain fell at the city's airport, and nearby Plaquemines Parish, La., suffered extensive flooding when storm surge and heavy rainfall pushed water over levees.

Although Isaac quickly weakened to a tropical storm after landfall, it caused five deaths in Louisiana and Mississippi, and knocked out power for an estimated 900,000 customers across five states, including portions of New Orleans. The city's levee system, rebuilt after Katrina, remained intact last week.

The death toll on the Gulf Coast was less than the 29 people killed from the tropical storm that first hit the Dominican Republic and Haiti, as the storm made its way through the Caribbean.

Oakland, Calif.-based catastrophe risk modeling firm Eqecat Inc. estimated U.S. onshore insured losses as high as $1.5 billion while Boston-based AIR Worldwide Corp. estimated them as high as $2 billion.

Tim Doggett, principal scientist at AIR, said the slow-moving storm dumped up to 25 inches of rain over a 36-hour period in certain areas of the Gulf Coast.

“This is definitely not your standard Category 1 hurricane,” Mr. Doggett said. “The longevity has been pretty noteworthy.”

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“Typically, you wouldn't expect much damage with a Category 1 (hurricane), but with a longer duration, (structural) fatigue builds up over time and you get damage you wouldn't see otherwise,” he said. “We may see more tree damage that you might expect” due to the heavily saturated soil.

Isaac's lengthy stay along the Gulf Coast delayed getting claims adjusters on the ground to assess the damage.

Tom Larsen, senior vice president and product architect at Eqecat, said a thorough accounting of Isaac-related insured losses likely will take months, adding that it took years to sort out claims in the wake of Katrina.

“These are very difficult types of events to estimate,'' Mr. Larsen said. “It's far easier to estimate a loss when everything's wiped out.”

As for the offshore oil and gas industry, AIR, citing U.S. Bureau of Safety and Environmental Enforcement data, said 505 platforms and 50 rigs were evacuated in advance of Isaac. AIR and Eqecat said last week they had not yet estimated insured offshore losses.

“Offshore platforms are owned by a very complex set of ownership groupings, so it's very difficult for us to provide a salient loss estimate,” Eqecat's Mr. Larsen said.

Terry Leone, New York-based senior industry analyst at SNL Financial L.C., said that, while significant, the losses resulting from Isaac are unlikely to greatly affect insurers' balance sheets.

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“Commercial property writers will be affected, but the losses should not be too large for any of the companies to handle,” Mr. Leone said. “Another thing to note is that much of the damages appear to be caused by flooding, and flood losses are mainly insured by the federal government and may not have much impact on insurance companies.”

J. Nicholas Ciabattoni, vice president-claim home officer property and U.S. marine at Chicago-based CNA Financial Corp., set up a center in Nashville, Tenn., to handle business-related Isaac claims.

“In addition to our group of general adjusters, we have a specialized team for large losses,” Mr. Ciabattoni said.

“We overlay the wind fields associated with the storm with our geocoded properties,” he said. “This gives us a view of how different customers are impacted in different areas and helps us know how to deploy our people.”