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
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.
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
IN PICTURES: Springtime flooding in the US
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
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
Specialists attribute the difference in fatalities to better
storm and flood forecasts, along with improved approaches to flood
Outdated flood-risk maps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hazards remain based on outdated flood-risk maps - something the US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.
Long-term flood records seem to tell a similar story, notes
Mathias Collins, a hydrologist with the National Marine Fisheries
Service's Restoration Center in Gloucester, Mass. …