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USGS South Atlantic Water Science Center - Georgia E-News Archive, 2009-2010

Archived E-News: 2009-2010 | 2006-2008

May. 3, 2010:
USGS South Atlantic Water Science Center - Georgia Installs Video Webcam at Peachtree Creek in Atlanta

The USGS South Atlantic Water Science Center - Georgia has installed a webcam at Peachtree Creek in Atlanta to allow you to view, in real time, the current river-stage conditions. The camera shows live video of streamflow conditions at this highly urbanized monitoring site that is very prone to rapid rises in stream stage and large-scale flooding. You can even take temporary control of the camera and adjust the pan, tilt, and zoom.

The Peachtree Creek WaterWatch URL is http://ga.water.usgs.gov/peachtree/

This service is funded by the USGS National Streamflow Information Program.


Feb. 11, 2010:
USGS South Atlantic Water Science Center - Georgia Installs Video Webcam at Peachtree Creek in Atlanta

New features were just released for the USGS WaterWatch real-time pages that significantly add value to the streamgaging information provided. Now you can see real-time bar graphs (similar to flood tracking charts), real-time forecast hydrographs from the National Weather Service, and a graphical shift-adjusted rating curve. Here are step-by-step instructions:

(1) Go to http://waterwatch.usgs.gov/?m=real&r=ga&w=flood%2Cmap

(2) In the past, you hovered over a site dot and clicked to view site summary information. Now, after you hover for a few seconds, you should click. You will yhen see a popup balloon with 5 tabs:

  • Summary information
  • Hydrograph
  • Peak flows: shows highest peak within last year and the 4 highest peaks ever
  • Forecast: National Weather Service forecast stream stages
  • Shift-adjusted ratings

If you have any questions or comments regarding these new features, please email Brian McCallum at bemccall@usgs.gov or call 770.903.9127.


Jan. 12, 2010:
Summary of Hydrologic Conditions in Georgia 2008 and Water Resources Data for Georgia, Water Year 2008 Now Available

The USGS South Atlantic Water Science Center - Georgia is pleased to announce the availability of "Summary of Hydrologic Conditions in Georgia 2008" factsheet by Knaak and others. This fact sheet provides a concise summary of streamflow, reservoir, and groundwater aquifer conditions throughout the 2008 water year. It is intended to accompany the 2008 annual data report for Georgia that (previously available online) contains daily data for each monitoring location.

To access the Summary of Hydrologic Conditions in Georgia, 2008, click: http://pubs.usgs.gov/fs/2009/3109/

To access the Water Resources Data for Georgia, Water Year 2008, click: http://wdr.water.usgs.gov/wy2008/search.jsp


Nov. 4, 2009:
Summary of Hydrologic Conditions in Georgia 2008 and Water Resources Data for Georgia, Water Year 2008 Now Available

Atlanta Floods Extremely Rare

The epic flooding that hit the Atlanta area in September was so extremely rare that, six weeks later this event has defied attempts to describe it. Scientists have reviewed the numbers and they are stunning.

“At some sites, the annual chance of a flood of this magnitude was so significantly less than 1 in 500 that, given the relatively short length of streamgaging records (well less than 100 years), the U.S. Geological Survey cannot accurately characterize the probability due to its extreme rarity," said Robert Holmes, USGS National Flood Program Coordinator. “Nationwide, given that our oldest streamgaging records span about 100 years, the USGS does not cite probabilities for floods that are beyond a 0.2 percent (500-year) flood.”

“If a 0.2 percent (500-year) flood was a cup of coffee, this one brewed a full pot,” said Brian McCallum, Assistant Director for the USGS South Atlantic Water Science Center - Georgia in Atlanta. “This flood overtopped 20 USGS streamgages – one by 12 feet. The closest numbers we have seen like these in Georgia were from Tropical Storm Alberto in 1994. This flood was off the charts.”

The rains returned water levels in the region’s two largest reservoirs, Lake Lanier and Allatoona Lake, to pre-drought levels. Lake Lanier rose by more than three feet to 1068 feet by Sept. 25 and returned to full pool in October. Allatoona Lake rose to 853.25 feet on Sept 23, more than 13 feet over full pool of 840 feet.

“The flooding in Atlanta is certainly near the top of the list of the worst floods in the United States during the past 100 years,” said Holmes. “For comparable drainage areas, the magnitude of this flood was worse than the 1977 Kansas City flood, which caused tremendous destruction and loss of life. It is a testament to the diligence of county officials and emergency management teams that more lives were not lost in Georgia.”

Significant property losses, however, were a near certainty from this event. According to the National Weather Service, some locations recorded up to 20 inches of rain from 8:00 pm on Sept. 20 to 8:00 pm the following day. Culverts and sewers are not usually designed for events of this magnitude because they are so rare and it is cost prohibitive.

“Applying rainfall frequency calculations, we have determined that the chance of 10 inches or more occurring at any given point are less than one hundredth of one percent”, said Kent Frantz, Senior Service Hydrologist for the National Weather Service at Peachtree City. “This means that the chance of an event like this occurring is 1 in 10,000.”

For this analysis, USGS reviewed high-water-mark surveys and indirect peak discharge computations throughout the flood-affected region. Scientists gather these data from the field during floods and in their immediate aftermath to supplement or in this case, to provide data after a gage is destroyed. Some notable results:

  • In Cobb County, Sweetwater, Noonday, Butler, and Powder Springs creeks flooded so severely that the annual chance of a worse event is far smaller than 0.2 percent (500-year) flood. On Sweetwater Creek near Austell, Ga., high-water marks showed a peak stage of 30.8 feet. The peak flow (31,500 cubic feet per second) was more than double the previous peak flow recorded at this site during the last 73 years. The previous peak, caused by the remnants of Hurricane Dennis in July 2005, was almost 10 feet lower at 21.87 feet.
  • In Douglas County, the Dog River near Fairplay overtopped the USGS stream gage by 12 feet. The peak stage was 33.8 feet, with a peak discharge of 59,900 cubic feet per second. This is well beyond the 0.2 percent annual exceedence probability (500-year) flood.
  • Gwinnett, DeKalb and Rockdale counties also had record flooding. Suwanee Creek floods were beyond the 0.2 percent annual exceedence probability (500-year) flood.
  • On the Chattahoochee, the USGS gage at Vinings reached a peak stage of 28.12 feet with 40,900 cubic feet per second, which represents between a between a 1.0 to 0.5 percent annual exceedence probability (100- to 200-year) flood. In Georgia the USGS maintains a network of nearly 300 streamgages that provide data in real time. Data from these streamgages are used by local, state and federal officials for numerous purposes, including public safety and flood forecasting by the National Weather Service. A map of these gages and graphs of discharge for the last seven days is available online.

The USGS works in cooperation with other Federal, state, and local agencies, throughout Georgia that measure water level (stage), streamflow (discharge), lake levels and rainfall.


Oct. 19, 2009 :
Streamgages Podcast

The USGS has just released an informational online podcast called "Streamgages: The Silent Superhero" that you may find interesting. The USGS South Atlantic Water Science Center - Georgia, in cooperation with many Federal, State, and local agencies, operates nearly 300 real-time streamgages across the State. These streamgages provide the latest river levels and streamflows each hour automatically to the USGS NWISWeb pages at http://waterdata.usgs.gov/ga/nwis/rt

The data provided by these streamgages have been critical throughout the recent prolonged drought as well as the historic floods this past spring in South Georgia as well as the epic floods in the metropolitan Atlanta area this September. If you have any questions regarding the USGS streamgaging program in Georgia, please contact Brian McCallum at (770) 903-9127 or via email at bemccall@usgs.gov

To view the podcast, please click on the following link: http://www.usgs.gov/corecast/details.asp?ep=106


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