Category Archives: ISSUES

Issues about water

Atlanta Floods Extremely Rare

ISSUES

New USGS Release: Atlanta Floods Extremely Rare

USGS Georgia Water Science Center E-News

November 4, 2009

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 Georgia Water Science Center 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:

Ø 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.

Ø 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.

Ø Gwinnett, DeKalb and Rockdale counties also had record flooding.  Suwanee Creek floods were beyond the 0.2 percent annual exceedence probability (500-year) flood.

Ø 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.

For more information about USGS activities in Georgia, please visit http://ga.water.usgs.gov/

Another good reason for Green Infrastructure!

September 2009 Flooding and E. Coli Bacteria Sampling

ISSUES

USGS Georgia Water Science Center E-News

September flooding and E. coli bacteria sampling

Oct. 1, 2009

Indicator bacteria levels in the Chattahoochee River increased substantially during and after the epic flooding that struck Atlanta on September 22-23, 2009. On September 14, 2009, the Upper Chattahoochee Riverkeeper collected water samples from the Chattahoochee River at West Paces Ferry Road in Vinings that contained an Escherichia coli (E. coli) bacteria density of 75 most probable number per 100 mL. Multiple water samples collected from the river at West Paces Ferry Road by the USGS on September 23, 2009 were nearly 200 times higher than the value measured on September 14, 2009. The USGS sampled three additional sites downstream from Vinings on September 23, 2009.

Sample date  / Location  / E. coli density (most probable number per 100 mL)

9/14/2009 Chattahoochee River at West Paces Ferry Rd   75

9/23/2009 Chattahoochee River at West Paces Ferry Rd   14,000

9/23/2009 Chattahoochee River at Interstate 20   18,000

9/23/2009 Chattahoochee River at Fairburn, GA   3,900

9/23/2009 Chattahoochee River at Whitesburg, GA   1,100

The National Park Service and the Upper Chattahoochee Riverkeeper collected water samples from the Chattahoochee River and Big Creek on September 28 and 30, 2009. These values show substantial decreases in E. coli density within 7 days of the flood.

Sample date  / Location  / E. coli density (most probable number per 100 mL)

———————————————————————————————————————

9/28/2009 Chattahoochee River at Medlock Bridge Rd near Norcross  370

9/28/2009 Chattahoochee River at Roswell Road   1,420

9/28/2009 Chattahoochee River at Johnson Ferry Rd   785

9/28/2009 Chattahoochee River at West Paces Ferry Rd   760

9/30/2009 Big Creek at Roswell Mill   170

9/30/2009 Big Creek at Riverside Park 130

9/30/2009 Chattahoochee River at Johnson Ferry Rd 140

9/30/2009 Chattahoochee River at South Cobb Dr.  >24,196

For more information about USGS activities in Georgia, please visit http://ga.water.usgs.gov/.

Another good reason for Green Infrastructure!

The Hydro-Illogical Cycle

ISSUES, MY THOUGHTS, TRIVIA

“We welcome the first clear day after a rainy spell. Rainless days continue for a time and we are pleased to have a long spell of such fine weather. It keeps on and we are a little worried. A few days more and we are really in trouble. The first rainless day in a spell of fine weather contributes as much to the drought as the last, but no one knows how serious it will be until the last dry day is gone and the rains have come again.”

(from I.R. Tannehill, Drought: Its Causes and Effects, Princeton University Press, Princeton, New Jersey, 1947)

 

Unlike other natural disasters, drought does not have a clearly defined beginning and end. As a result, our reaction to drought traditionally has not been timely.

©2006 National Drought Mitigation Center

Rain Barrels

ISSUES, MY THOUGHTS, SOLUTIONS

Rain Barrels are a great introduction to the world of Rainwater Harvesting. However, they are only good for small gardens or patios. If you are just suplimenting the occasional dry week great, but if you want be ready for the next drought or long dry period get a tank. Look at your local rainfall history. Start planning 3-4 weeks of reserve and leave room for another tank down the line.

Also take a look at my rain barrel page at the top to find out good tips on building your own or what to look for when you buy one. Remember, have at least one 1 1/2″ overflow directed away from the house and ending in an area that will not erode. Secondly, make sure your barrel is opaque so not to allow sunlight to cause an algae bloom.

Steve

Federal Judge Rules Against Ga. in Water Litigation

ISSUES

By Bill Rankin

The Atlanta Journal-Constitution

A federal judge on Friday ruled the U.S. Army Corps of Engineers has been illegally reallocating water from Lake Lanier to meet metro Atlanta’s needs, but he’s not turning off the tap just yet.

The judge overseeing the high-stakes case wants a political solution and is sending the fight to Congress.

In the meantime, the current withdrawal levels from Lake Lanier will be allowed to stay the same — but not increase, U.S. District Judge Paul Magnuson ruled. And if a political solution cannot be worked out in three years, the judge said, his order will take effect.

This means the metro area will not be allowed to use Lake Lanier as its primary source of water supply.

“Thus…only Gainesville and Buford will be allowed to withdraw water from the lake,” Magnuson said in a 97-page order. “The court recognizes that this is a draconian result. It is, however, the only result that recognizes how far the operation of the Buford [Dam] project has strayed from the original authorization.”

Magnuson, of St. Paul, Minn., was picked in 2007 to decide the almost two-decades-old tristate water wars case involving Georgia, Alabama and Florida.

His ruling handed the metro area a crushing legal defeat. The judge found that the Corps of Engineers should have obtained congressional approval before allowing Lake Lanier to be the metro area’s primary source of water supply.

In a joint statement, Georgia senators Johnny Isakson and Saxby Chambliss acknowledged it is now up to Congress to reach a compromise.

“We will work tirelessly to reach an agreement that is in the best interest of Georgia while at the same time respecting the interests and concerns of Florida and Alabama,” the senators said. “This is a huge challenge, but it is a challenge we must meet.”

Alabama Gov. Bob Riley praised the ruling, saying he hopes it leads to renewed negotiations between the three states and a “fair and equitable” agreement.

“Atlanta has based its growth on the idea that it could take whatever water it wanted whenever it wanted it, and that the downstream states would simply have to do with less,” Riley said. “Following the court’s ruling today, this massive illegal water grab will be coming to an end.”

Gil Rogers, senior attorney with the Southern Environmental Law Center, said the ruling puts Georgia in a much weaker negotiating position with respect to Lake Lanier water rights.

“This is a real wakeup call for the metro Atlanta area,” he added. “Drought or no drought, this area can no longer take water for granted and should move as quickly as possible to sustainable water management practices that do not involve controversial reservoirs.”

Magnuson said he was sympathetic to the plight of the Corps of Engineers because it has to deal with competing claims to Lake Lanier’s water — a finite resource.

But the judge said the Corps’ reallocation of Lake Lanier’s water without congressional approval was illegal and in violation of the Water Supply Act. And Magnuson said it was “beyond comprehension” that the Corps’ current operating manual for the Buford Dam is more than 50 years old.

He encouraged the Corps to update its water supply plans so those in the Apalachiocola-Chattahoochee-Flint (ACF) river basin can determine how the operation of Buford Dam will affect their future interests and whether it can meet their water needs.

But Magnuson also said the blame cannot be placed solely on the Corps’ shoulders.

“Too often,” Magnuson wrote, “state, local and even national government actors do not consider the long-term consequences of their decisions. Local governments allow unchecked growth because it increases tax revenue, but these same governments do not sufficiently plan for the resources such unchecked growth will require.”

Nor do individual citizens consider frequently enough their own water consumption, absent a crisis such as the recent drought, the judge said.

“The problems faced in the ACF basin will continue to be repeated throughout this country, as the population grows and more undeveloped land is developed,” Magnuson said. “Only by cooperating, planning and conserving can we avoid the situtations that gave rise to this litigation.”