How to monitor Georgia flood gages online

Editor’s Note: This post is guest authored by Jonathan W. Musser and Anthony J. Gotvald of the U.S. Geological Survey, Georgia Water Science Center in Norcross, Ga. In this post, Musser and Gotvald describe several web-based platforms available for monitoring flood inundation gages in Georgia. Using these platforms, the U.S. Army Corps of Engineers is working with USGS to develop new flood inundation maps for parts of Georgia.

 

Interactive websites and digital maps of flood inundation for select areas in Georgia are available on sites hosted by the U.S. Geological Survey (USGS) and the National Weather Service (NWS). The mapped and modeled areas to date include the Flint River in Albany, Peachtree Creek in Atlanta, Sweetwater Creek in Cobb and Douglas Counties, and Suwanee Creek in Gwinnett County.

This map shows locations of gages in Georgia equipped with flood-inundation mapping.

This map shows locations of gages in Georgia equipped with flood-inundation mapping.

Flood-inundation maps are posted on the NWS Advanced Hydrologic Prediction Service (AHPS) website and on the USGS Flood Inundation Mapper (FIM) website.

The inundation maps provide water-surface elevations in relation to the North American Vertical Datum of 1988 (NAVD 88) and show flood extent and water depths, so emergency managers and the public can see and prepare for potential flooding.

Screen capture of the National Weather Service Advanced Hydrologic Prediction Service website for the Flint River, Albany, Ga. (ABNG1).

Screen capture of the National Weather Service Advanced Hydrologic Prediction Service website for the Flint River, Albany, Ga. (ABNG1).

The AHPS flood-inundation website, shown above, has background map images obtained from the Google Maps satellite with multiple zoom levels. Water depth is color coded in shades of blue, and the transparency level can be modified. Additional gage information, such as flood categories, flood-impact statements, and forecasts can be obtained at this site. Other tabbed information available at this website include Hydrograph, River at a Glance, Download, Weekly Chance of Exceeding Levels, and Chance of Exceeding Levels During Entire Period.

A screen capture of the USGS Flood-Inundation Mapper website for Peachtree Creek, Atlanta Ga. (USGS stream gage 02336300)

A screen capture of the USGS Flood-Inundation Mapper website for Peachtree Creek, Atlanta Ga. (USGS stream gage 02336300)

The USGS FIM website, shown above, depicts flood-inundated areas on a choice of backgrounds (street map, satellite imagery with labels, or topography) as well as additional information about the streamgaging location and the area(s) of inundation. Once a streamgage is selected, an information window is displayed that includes additional tabbed information the user may find helpful. The first tab is Flood Tools, which include one or two slide bars to set the gage height and elevation at the streamgage(s). The inundated area changes based on the streamgage heights. The second tab displays recent hydrograph(s) for the streamgage(s). The third tab provides access to the NWS prediction for the streamgage. The fourth tab provides access to the U.S. Environmental Protection Agency Hazus data for the site if it exists. The next two tabs show images from webcams, if they exist, and the final tab provides information about the site, including published reports.

Other tools included with the FIM mapper are zoom history, latitude and longitude connected to the mouse pointer, a search engine, and additional layers which can be displayed, such as NWS radar, flood watches and (or) warnings, and AHPS forecast sites.

The U.S. Army Corps of Engineers Savannah District is currently developing flood inundation maps for the Chattahoochee River in Atlanta and the Ocmulgee River in Macon. The USGS is collecting peak water-level data using self-logging sensors that are deployed along the channel reaches of both these study areas. The water-level data will be used to calibrate the USACE models that are used to develop the flood inundation maps. The flood inundation maps will be hosted on the AHPS and FIM websites.

About US Army Corps of Engineers Savannah District

The U.S. Army Corps of Engineers Savannah District oversees a multi-million dollar military construction program at 11 Army and Air Force installations in Georgia and North Carolina. We also manage water resources across the Coastal Georgia region, including maintenance dredging of the Savannah and Brunswick harbors; operation of three hydroelectric dams and reservoirs along the upper Savannah River; and administration of an extensive stream and wetland permitting and mitigation program within the state of Georgia. Follow us on Twitter @SavannahCorps and on Facebook.com/SavannahCorps
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