preparing for the new high water mark.

It’s been over a month since rain-swollen creeks tore through roads and flooded homes in Colorado’s Front Range. While the camera crews have long since gone home, the disaster isn’t over for families who suffered property damage. Of the 20,000 single-family homes in the Boulder area, only 3,504 had flood insurance – one of the highest ratios in Colorado. Four thousand homes were damaged in Boulder alone.

Homes within the 100-year flood zone backed by federal mortgages are required to purchase flood insurance, often at subsidized rates, through the National Flood Insurance Program, an arm of the Federal Emergency Management Agency. But September’s flooding swamped uninsured Colorado homes well above the 100-year floodplain – just as homes in New York and New Jersey outside the flood zone were swamped by Hurricane Sandy last year, and Vermont homes were sunk by Tropical Storm Irene the year before.

Typically, a 100-year flood has a 1 percent chance of happening in a given year. As climate change continues to push weather patterns toward extremes, though, many climatologists are finding these once-in-a-lifetime weather events to occur more frequently: A report released last month by the National Oceanic and Atmospheric Administration found that human-induced climate change played a role in several extreme weather events of 2012. There’s been a push among climate scientists and private insurance agencies to update federal flood maps to reflect what HCN contributing editor Craig Childs calls the “new high water mark:” areas beyond historical flood zones that are now at risk of flooding due to rising sea levels, different runoff patterns and more intense storms.

"Old statistics on flood risk are obsolete," Kevin Trenberth, a senior scientist at the National Center for Atmospheric Research, told InsideClimate News. "Increasingly, (FEMA) should be looking ahead."

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