During February 2001 the flood
project team continued to work on revising available DEMs (from NMD) by
topographic quadrangle for the Flint River Basin in the vicinity of
Manchester and Thomaston in the northern part of the Flint River
Basin.
The revision is done by digitizing topographic contours from
7.5 minute topographic maps, gridding the area to suitable resolution,
and preparing new DEM’s for each map.
The new DEMs were inserted into the basinwide DEM,
constructed earlier.
The November 2000
flood inundation model indicates spotty flooding within the 100 year
floodplain, in the vicinity of Manchester and Tomaston, Georgia, as shown in figure
1. The revised flood
inundation model run (February 12, 2001) produced a new 100 year
floodplain as shown in figure 2.
The boundaries of this revised
floodplain model compare quite well with estimated base flood
elevation data. The improved floodplain (figure 2) illustrates
the importance of completing the process of DEM revision to produce a
regionally accurate and consistent DEM for the river basin prior to
beginning any comparative, qualitative analysis.
The DEM revision work is being shared
with NMD by the flood team and the Georgia Tech GIS Clearinghouse (GTCH)
digital orthophotography team which is working on an active and
complementary (USGS cooperative) project to prepare color DOQs for the
state of Georgia.
These DOQ’s will aid the flood team with the planned future
flood inundation visualization capabilities.
The ongoing liaison with NMD is
needed to improve the process of DEM development in order to begin the
organized support of hydrologic applications, such as flood inundation
modeling. The plan is to
begin to establish and to refine the process using the DEM’s of the
Flint River Basin. NMD
has offered to partner with the state of Georgia to improve available
DEM’s.
The flood team will
meet in March at Georgia Tech with CINDI representatives, Georgia District Chief, Ed Martin, SE
Regional SW Specialist, Larry Bohman, and
Nick Faust of GTRI for briefings and review.
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U.S. Geological Survey