PEMBROKE, N.H. --
A new flood preparedness tool that will help
emergency managers improve flood warnings and response is now available for a
16.5-mile reach of the Suncook River in southeastern New Hampshire that has
frequently flooded adjacent homes.
The new web-based tool, developed by
U.S. Geological Survey scientists, shows flood inundation maps to identify
where the potential threat of floodwaters is greatest. The maps show the land
areas and features that would likely be submerged and the expected depth of the
floodwaters when a streamflow gauge upstream rises. The maps are part of
a national USGS effort to help emergency managers quickly assess evacuation
routes, determine when and how to evacuate residents threatened as floodwaters
rise, and better focus flood response and recovery efforts.
"Floods are the most expensive
natural disaster that we face in the U.S., affecting all 50 states and costing
more than $2.7 billion dollars annually averaged over the past 10 years
according to government estimates," said USGS Director Marcia McNutt.
"Investing in science-based preparedness tools like the online flood
inundation maps is a smart way to help everyone know the quick decisions to
make to spare lives and property."
The USGS is partnering with the
National Weather Service, the U.S. Army Corps of Engineers and FEMA to develop
comparable flood inundation maps in locations across the country identified to
be at high risk for flooding.
The USGS completed the Suncook River
maps in partnership with the New Hampshire Department of Safety, Division of
Homeland Security and Emergency Management. The maps extend from the USGS streamgage
at Depot Road in North Chichester to the Merrimack River. They
include portions of the towns of Chichester, Epsom, Allenstown, and Pembroke
and the community of Suncook. The maps show the extent and depth of flooding
expected in these towns, for 10 river levels, starting when the North
Chichester gauge reaches seven feet, up to a crest of 18 feet. Flood
stage is at seven feet.
"I see these maps as a great
new tool for local and state emergency personnel, residents, and landowners to
prepare for, and respond to flooding," said Christopher Pope, Director of
the NH Division of Homeland Security and Emergency Management.
The North Chichester streamgage is
also a National Weather Service flood forecast gauge. The NWS combines
the current stage with its precipitation forecasts to predict the Suncook
River’s crest at this location. Based on these predictions, anyone can
use the new flood inundation maps to estimate areas along the Suncook River
that would be flooded.
"A number of recent
studies of the Suncook River since the flooding of 2006 and 2007 made the flood
inundation mapping possible," said Robert Flynn, USGS hydrologist and
author of the maps.
The area of the Suncook River shown
on the maps has flooded many times, most notably in 2006, 2007, and 2010. On
May 15, 2006, the flooded river changed course, forming a new river channel
through a sand and gravel pit, shortening the river’s length, and increasing
the potential flood hazards to communities downstream.
"This shortening of the river
means that there is a greater potential for flooding to adjacent communities
because of faster river flows in the vicinity of the sand pit, greater erosion
of the river banks and stream channel, and piling up of sediment
downstream," said Flynn.
The flood inundation map web-based
tool can be found online.
The Suncook River inundation report, which contains links to current USGS
stream-stage data and forecasted stream-stage data from the NWS, is
available online. NWS
forecasted flood levels for the Suncook River are available online.
The Flood Inundation Map is one of a
series of flood preparedness tools that the USGS has developed to help
emergency and resource managers and the public prepare for potential flooding
and track water levels as they rise. The map is based on data from
the USGS's nationwide streamgage network that monitors the water level and
flow of the nation's rivers and streams.
WaterAlert and StreaMail are
two other online resources that provide residents with timely information about
river conditions at important locations. Subscribers have a number of options
to choose from on how to get the information, and can have emails or texts sent
to them automatically whenever a critical threshold is reached. With these
tools, emergency managers, resource managers and the public can stay informed
and help keep themselves or others out of harm's way by keeping up to date of
local conditions.