Albemarle-Pamlico Sounds
LANDSAT 7 thematic mapper (TM) images combined with digital elevation model
(DEM) data
Type: Extent of
habitat (i.e., area of habitat and whether there has been a decline) and stressors
affecting habitat (i.e., which sources have contributed to its degradation and
whether they are direct or indirect factors).
Category: Upland
Cost: Information not provided.
Description: Capturing the extent of flooding during Hurricane Floyd
in an efficient manner is essential for response, recovery, and mitigation activities.
An efficient and economical method for mapping flood extent in a coastal floodplain
was based on classifying water and non-water features on two Landsat 7 thematic
mapper (TM) images (acquired before and during the flood event), then performing
a change detection analysis to identify floodwaters. Digital elevation model
(DEM) data were also integrated into the analysis to model floodplain inundation
and identify flooded areas underneath forest canopies.
A simple and efficient method for mapping flood extent in a coastal floodplain
was developed. The method was based on classifying water and non-water areas
on two Landsat 7 TM images, performing a change detection analysis to determine
flooded areas, and incorporating the representation of flooding according to
the inundation of a DEM. Inclusion of the DEM data into the analysis overcame
the limitation of the TM data in being able to distinguish between flooded areas
and forest canopy. Assessment of the flooded and non-flooded areas was undertaken
using ground verification and interpretation of aerial photography taken during
the flooding. The land use and land cover categories most affected by the flood
were: bottomland forest/hardwood swamps, southern yellow pine, and cultivated
land.
Outcome: The objective of this research was to develop a method for mapping
flood extent using data that was accessible, inexpensive, and relatively easy
to process. The method developed here has been shown to be reliable and could
be used in the other coastal floodplains (such as the East Coast, and the Gulf
Coast of the U.S.), using similar TM images, DEM data, and river stage data.
Within Pitt County, North Carolina, the primary land cover types most affected
by flooding were bottomland forest/hardwood swamps, southern yellow pine, and
cultivated land. The method proved to be reliable and could be applied quickly
using data that are relatively inexpensive, easy to obtain, and easy to analyze.
This method should work well in similar areas of large spatial extent and flat
terrain.
Contact: Jeffrey D. Colby, Yong Wang, Karen Mulcahy, Department of Geography,
East Carolina University, Greenville, NC 27858, E-mail: colbyj@mail.ecu.edu
Citations: · Quick Response Report #126, Hurricane Floyd Flood Mapping
Integrating Landsat 7 TM Satellite Imagery and DEM Data and http://www.colorado.edu/hazards/qr/qr126/qr126.html
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