USGS - science for a changing world

Center for Spatial Analysis Technologies



Flood Inundation and Visualization Project:
March 2001 Status Report



During March 2001 the project team continued to work on revising available DEMs (from NMD) by topographic quadrangle for the Flint River Basin. 1:24,000-scale hypsography currently revised for the basin was combined with the 1:24,000-scale hydrography (edited by the project team to spatially represent downstream flow) to begin to produce level-2 DEMs constrained with hydrography.
  • Level 2 DEMs are elevation data sets that have been processed or smoothed for consistency and edited to remove identifiable systematic errors. A 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 are being inserted into the basinwide DEM at a 10-meter grid spacing. Figure 1 shows the status of this effort.

Figure 2 shows the comparison of 10-meter grid flood inundation models using the original level 1 DEMs and the enhanced level 2 DEMs in the vicinity of Woodbury, Georgia. Note: the large area north of Woodbury depicted as flooded from the original DEMs is eliminated using the level 2 DEMs. This new flood inundation area matches the Estimated Base Flood Elevation (EBFE) developed after Tropical Storm Alberto in 1994.

The City of Albany in cooperation with Georgia Emergency Management Agency (GEMA) produced one-foot contours throughout much of the flood plain in the city. DEMs with 3-meter grid cells were developed using these one-foot contours. Figure 3 shows a 3-meter grid flood inundation model for the City of Albany based on these new data. This elevation data were also inserted into the basinwide DEM for the Flint River Basin.

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 project team (Bob Dyar, Jack Alhadeff, Jonathan Musser and Mark Landers) met on March 29th at Georgia Tech with CINDI representatives, Jim Preacher and Susan Clark and USGS Chief Scientist for Geography, John Kelmelis, Georgia District Chief, Ed Martin, USGS Mapping Laison for Georgia, Mike Callahan, and Georgia Tech Research Institute Senior Scientist, Nick Faust for briefings and review.

On March 20th, the project team briefed Terry Lunn, Michael Newman, and David Gonzalez of the Georgia Emergency Management Agency on the project.

On March 21st, the project team briefed Mike Callahan on the need for improved DEMs for the State of Georgia and are developing a statement of work to acquire these data.

John Kelmelis, Susan Clark, and Jim Preacher Mike Callahan and Ed Martin
John Kelmelis, Susan Clark, and Jim Preacher Mike Callahan and Ed Martin
Nick Faust demonstration Nick Faust
Nick Faust demonstrating visualization of flood information Nick Faust
status map of DEM quadrangles

Figure 1: Status map of quadrangles
floodplain comparison near Woodbury, GA

Figure 2: Comparison of area in the vicinity of Woodbury, GA using Level-1 (March 2001) and Level-2 (April 4, 2001) DEMs.
floodplain near Albany, GA using one-foot contours

Figure 3. Albany flood model using 3-meter grid cells based on one-foot contours.


Return to CINDI Project Home Page
Return to CSAT Home Page

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://csat.er.usgs.gov/cindi/mar2001.html
Page Contact Information: webmaster-ga@usgs.gov
Page Last Modified: Tuesday, 23-May-2006 11:23:54 EDT