NASA scientists have teamed up with researchers in North
Carolina in an effort to get relief for the people who find
themselves under siege each year by floodwaters spawned by
strong Atlantic hurricanes.

The storms bring high winds, storm surges and heavy rains,
and the resulting floods force massive evacuations,
threatening the lives of thousands of residents.

Using instruments on satellites and airplanes, NASA provides
data used to create highly accurate maps of suspected flood
zones that can help the state’s emergency management services
better prepare for future storms.

In 1999, back-to-back impacts from Hurricanes Dennis and
Floyd wreaked havoc on North Carolina’s eastern coastal
plain. Over a nine-day period, Hurricane Dennis ravaged North
Carolina with torrential rains and 70 mile-per-hour winds.
Ten days later, Hurricane Floyd, twice the size of typical
Atlantic hurricanes, made landfall, dumping upwards of 18
inches of rain in the same geographical areas.

Combined, the two hurricanes claimed 51 lives and caused more
than $6 billion in damages.

Soon afterwards, state officials turned to scientists at
NASA’s Stennis Space Center in Mississippi, the agency’s lead
center for Earth Science Applications. “Initially, the state
of North Carolina asked NASA for technical assistance in
coordinating contacts with other federal agencies in
obtaining remote sensing data — digital photographs taken
from an airplane or satellite — for flood mapping,” said Dr.
Ghassem Asrar, Associate Administrator for Earth Science at
NASA Headquarters in Washington.

“North Carolina was already one of the most sophisticated
states in the U.S. in the use of geographic information,”
said Dr. Bruce Davis, a geographer and acting chief of the
application research division of the Earth Science
Applications Directorate at Stennis. “The state, through its
Center for Geographic Information and Analysis, was well-
prepared to take advantage of remote sensing data.”

The flooding in North Carolina from Hurricanes Dennis and
Floyd was a devastating double punch to the region. “Many
deaths came after the storms as residents began to move
about, unaware rivers and creeks were rising as fast as six
to eight inches per hour,” Davis added. Hydrologists said the
probability of floods this severe occurs, on average, once
every 500 years.

“The rapid development that has occurred in North Carolina
over recent years with roadway construction, the alteration
of drainage basins and other build-outs began to impede the
flow of once-open streams,” Davis said. “The result was a
rapidly changing environment once the floodwaters began
flowing, and, even though officials worked hard to inform
people of the potential risk, the information in place at the
time of the two storms was not adequate to determine the
actual amount of risk related to the scene.”

“We assisted in the review of North Carolina’s quality
control plan for the development of digital elevation-model
products. We also engaged in pilot projects that gave the
state an initial look at the quality and utility of remotely
sensed data to be used for the development of improved
digital elevation models,” Davis said.

“With this statewide digital elevation model, we are looking
at informed methods of assessing the impact to be felt by
communities as they grow and develop,” said John Dorman,
North Carolina Administrator for Survey and Mapping. “The
accuracy of the elevation data will greatly assist in mapping
areas that might potentially become flooded in the future.”

North Carolina officials believe the work with NASA holds
great promise for future development and mapping of potential
flood zones. The type of research data collected by the
Stennis team could be used to model almost any coastal
region.

This activity was conducted as part of NASA’s Earth Science
Enterprise, a long-term research effort that studies how
human-induced and natural changes affect the global
environment while bringing real-world geospacial applications
to the American people.