 |
During the period of
April through July 2001, the
project team continued to work on revising available DEMs (from NMD) by
topographic quadrangle for the Flint River Basin. All existing
1:24,000-scale topographic quadrangles having existing digital
contours (hypsography), were combined
with the 1:24,000-scale hydrography to produce level-2 DEMs constrained
with hydrography. These included both USGS, NMD 1:24,000-scale
hypsography and project team scanned and tagged vector contour
quadrangles. In all a total of 55 Level 2 DEM
quadrangles having were produced. |
| Investigators Jack Alhadeff (l) and Mark
Landers (r) discuss project activities with USGS Director Chip
Groat (center) at Georgia Water Resources Conference in late
March 2001. |
- Level
2 DEMs are elevation data sets that have been processed or
smoothed for consistency and edited to remove identifiable
systematic errors. An RMSE of one-half contour interval is
the maximum permitted.
- Level
3 DEMs are derived from DLG data by using selected elements
from both hypsography and hydrography.
|
These new DEMs were inserted into the basinwide
DEM at a 10-meter grid spacing. Figure 1 shows the status of
this effort. Note: All quadrangles, depicted as smoothed in
previous status maps, were removed and replaced with Level 2
DEMs.
 |
Figure 1: Quadrangle status map |
A final 100-year RI flood model for
the Flint River Basin was developed as is shown in figure 2.
Using equations for 10-year and 50-year recurrence intervals (RI),
models of the 10-year and 50-year recurrence interval floods were
developed. Figures 3 and 4 show examples of these
families of RIs in the Peachtree City and Albany areas.
 |
Figure 2: Final 100-year RI flood model for the Flint River
Basin |
 |
Figure 3: 10-,50-, and 100-year RI flood models, Peachtree City, GA |
 |
Figure 4: 10-,50-, and 100-year RI flood models, Albany, GA |
Figures 5 and 6 show
estimated flood depth in the Peachtree City and Albany areas,
respectively. This calculation is based on the 100-year RI flood
model. This derivative of the model may be useful in assigning risk or
differentiating zones of risk.
 |
Figure 5: Estimated Flood Depth, in feet, Peachtree City, Georgia (100-year RI flood model) |
 |
Figure 6: Estimated Flood Depth, in feet, Albany, Georgia (100-year RI flood model) |
The determination of
flooding risk to roads, culverts, and bridges may be further explored
using the flood model. Figures 7 and 8 show roads that are
subject to flooding in the Peachtree City and Albany areas,
respectively. Also depicted on the illustrations are major highways
(Interstate, US and State Routes) that are also subject to flooding.
 |
Figure 7: Roads flooded from 100-year RI flood model, Peachtree City, Georgia |
 |
Figure 8: Roads flooded from 100-year RI flood model, Albany, Georgia |
|
U.S. Department of the Interior |
U.S. Geological Survey