How to plan better for New England floods
Changing rainfall patterns have increased the number and severity of floods. Better forecasts and improved flood management have helped, but planners need to do more to reduce risks and boost community resilience.
As flood waters recede in rain-soaked New England, March's record-smashing storms highlight the need for planners in the region to place an increased emphasis on reducing flood risks and boosting their communities' resilience to floods.Skip to next paragraph
In Pictures Springtime flooding in the US
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Focus not only should be placed on nuts-and-bolts, concrete-and-rebar projects such as upgrades to roads, bridges, culverts, and municipal drainage systems. Planners need to update the basic information on rainfall intensity they use to determine the adequacy of their projects.
That's the view of several hydrology specialists, who note that changing rainfall patterns in the area alone have increased the number of floods and appears to have increased their average severity as well over the past 40 years – particularly in the last decade.
The severe rainfall early this week rounded out a trio of intense rain storms during March. That sequence was unusual, acknowledges Paul Marinelli, who heads the US Army Corps of Engineers regional reservoir control center in Concord, Mass.
"But in the past five or six years we're getting to see more and more of this type of event," he adds, referring to the floods that coursed through the region.
Despite the hardship for large numbers of homeowners, business owners, cities, and towns in the areas hardest hit hardest hit by the region's floods, it could have been worse, Mr. Marinelli says. Winter snows in the region had long since melted by the time March's storms struck.
The last time the region experienced a similar one-month onslaught, more than 200 people in the region died due to floods. That was in August 1955, when two hurricanes struck within a week. In Boston, last months' rains topped the August 1955 total by 0.03 inches.
Specialists attribute the difference in fatalities to better storm and flood forecasts, along with improved approaches to flood management.
Outdated flood-risk maps
Still, several specialists say, existing estimates of flood hazards remain based on outdated flood-risk maps – something the US Federal Emergency Management Agency has been working to change with its program to improve map accuracy. But risks also are based on storm rainfall estimates tied to climate "norms" that no longer appear to be holding.
Storm numbers used for infrastructure design in the region were initially developed in 1961, then updated in 1993, explains Ellen Douglas, a professor and water-resources engineer at the University of Massachusetts at Boston.
"But a lot has changed," she says. Her research covering coastal regions of Massachusetts, New Hampshire, and Maine indicates that while the strength of extreme storms appears to be fairly constant between 1954 and 2005, "when you extend the record to 2008, extreme rainfall appears to be increasing." And the rate of increase appears to have grown between 1970 and 2008.