Nearly two years ago, Superstorm Sandy slammed into the U.S. East Coast with a ferocity that left more than 100 people dead and some 650,000 homes destroyed, and knocked out power to more than 8 million, weaving a path of destruction estimated to cost more than $65 billion.

But as damaging as it was, Sandy was far from the worst that nature can deliver, according to a new report from insurance giant Swiss Re which warns that the U.S. needs to prepare itself for storms that can cause $100 billion in damage or more -- because they've happened here before.

"Hurricane Sandy was obviously a terrible event for the Northeast United States, but it really was not the worst-case scenario," Dr. Megan Linkin, a natural hazards expert for Swiss Re and the report's author, said in an interview with The Huffington Post.

Waves break in front of a destroyed amusement park wrecked by Hurricane Sandy on Oct. 31, 2012, in Seaside Heights, New Jersey.

(Mario Tama/Getty Images)

While Sandy was an unusual storm -- it's been called a one-in-500-years event, largely because of the ways in which it interacted with the atmosphere and high tide, and its strange perpendicular, westward track -- it wasn't a particularly intense one, the report notes.

(MORE: Before & After Images of Sandy's Devastation)

Though it reached Category 3 on the Saffir-Simpson scale while over the ocean, making it officially a major hurricane, Sandy had weakened significantly by the time it made landfall along the coasts of New Jersey and New York, when it was classified as a post-tropical cyclone.

As a result, it lacked the kind of widespread strong winds and intense rainfall that often accompany hurricanes that hit the Northeast, the report adds.

That means we need to look to history to see just how big and powerful storms can get. Nearly 200 years ago, a storm much bigger than Sandy tore into the Mid-Atlantic and Northeast coasts, pummeling an area that stretched from Norfolk, Virginia, all the way to Boston.

Called the Norfolk and Long Island Hurricane of 1821, the storm made landfall on the North Carolina coast with winds of around 156 mph, and later struck the coastlines of Delaware, New Jersey and New York.

Were it to happen today, the storm would cause "50 percent more damage that Sandy and potentially cause more than $100 billion in property losses stemming from storm surge and wind damage," the report says.

Why? Because in 1821, the combined population of New York City and Washington, D.C., was only about 136,000. Today, more than 9 million people live in the two cities, with millions more spread across their now heavily developed metropolitan areas.

"Hurricane Sandy was a wake-up call," the report adds. "If left unheeded, the 1821 Norfolk and Long Island hurricane would be the nightmare."

Download and read the full report at Swiss Re.

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Long Beach Island, N.J.

In this aerial photograph, heavy equipment pushes sand to restore a barrier dune along the Atlantic Ocean on Long Beach Island, N.J., Friday, Nov. 9, 2012, after the region was pounded by Superstorm Sandy the previous week.