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3/23/2024
WT Staff
FLOOD SPECIAL REPORT
Georgia: Timeline of the river flooding in progress
Fifty Days of continuous flooding ends April 25, 2024
Thursday, March 15, 2024 updated Friday, April 26, 425 pm EDT
Spring 2024 flooding finally came to an end on April 25 at 515 pm. Brantley County is the setting for the last stand, settling 50 days of rogue flows sparked by March rains in the north and perpetuated by April storms in the south. During the spring flooding, the National Weather Service issued high fire danger warnings resulting from low relative humidity, a contradiction of climatic conditions.
In the beginning, Spring flood 2024
Rains in the north started the creeks and rivers rising in the first week of March with the first flooding recorded in the upper basins of the Atlantic and Mississippi/Gulf of Mexico basins on March 6. The flooding progressed through Georgia's watersheds from the creeks and streams depositing surface runoff into the major river systems. This article tracks the progress of the flood water through the watersheds, including time lapsed from one station to the next on the same river. By April 11, one last station remained above flood stage, the Satilla River, just an inch over at Atkinson. The steady declining flow trend indicated the end of Georgia's spring flooding when another round of thunderstorms and heavy rains set the south rivers overflowing again. As of this report, 15 stations are currently flooding on Day 40 of continous flooding in the state of Georgia.
In tracking the movement of flood flows through the watersheds, we note the time lapsed from the breach of flood stage in one location to the next. Most often, the progression is from north to south, from upstream to downstream on both sides of the state divide, this is the common direction for water to move across the face of Georgia. In some cases, the order of flooding occurs in reverse. These unorthodox progressions are worth noting, the Flint, the Altamaha and the Savannah Rivers are notable for instances of flooding uphill. Here is our report of the progression of the Spring 2024 flood, still spilling over in the south as of this update.
The USGS Waterwatch dashboard doesn't take long to light up when rain falls in the mountains. The colors representing flow volume change rapidly, from the red-brown of much below seasonal normal prevalent in the northwest over the winter, to lime green of a seasonal normal to blue of a high flow rating. Switching over to the flood panel, we begin to see the blue representing the highest recorded streamflows, 99th percentile, SMS alerts begin to go out when the creeks and rivers reach action stage, then the flood map takes on black tags as the monitors detect flows breaching flood stage.
In the day after the first high flows, action stage and active floodings, the creeks, streams and minor river tributaries are the first to overflow. These smaller vessels deposit their surplus volume rainwater runoff collected off the northern mountain landscape into the main river channels, the Chattahoochee and Flint Rivers on Gulf of Mexico side of the divide, the Oconee, Ocmulgee and Savannah Rivers for the Atlantic. For many days after the rain ends, even weeks after the initial inundation, the major veins of Georgia's surface flood in a fairly predictable and orderly march through the drainage basins, moving massive volumes of water and contaminants to their outlets at Atlantic Ocean and Gulf of Mexico.
Here is how the spring 2024 flood event has rolled out and carries on today in the Mississippi/Gulf and Atlantic basins of Georgia.
Atlantic Ocean basin
Twin rivers Ocmulgee and Oconee start south of the state divide in north Georgia, collecting rainfall runoff from creeks and minor tributaries of the central interior, eventually meeting and merging flow near Charlotteville to form the Altamaha River. Downstream on the Altamaha, the Ohoopee River jumps on, contributing thousands of cubic feet per second to the longest free flowing river on the US east coast. This is another way of saying, there are no dams on the Altamaha River.
By the time Altamaha reaches the Atlantic coast near Brunswick, surface water runoff from more than 14 thousand square miles is deposited into the ocean near Jekyll Island, note the permanent beach advisories for e.coli under the Georgia HABs button to the right of the map. In all this drainage area, these rivers are drinking water supply, the surface water sources for hundreds of thousands of Georgians.
Ocmulgee River drains an area over 5200 square miles of central Georgia before it joins the Oconee near Charlotteville. Oconee River drains a similar area just east of the state center line.
Of the twins, the Ocmulgee River commenced flooding first, taking the rainstorm runoff collected in Lake Jackson from 2200 square miles upstream. Lake Jackson receives flow from dozens of minor tributaries and creeks collecting runoff from dense urban landscape and developed municipal areas. Contaminants transported in heavy rain runoff from the urban areas is worth noting here. Over the course of one year, 2022, WTGA calculated over 10 million gallons of raw sewage was reported spilled from overflowing manholes caused by grease blockages and rags. All of this sewage entered creeks flowing to Lake Jackson.
Through this March 2024 flood event, we have tallied up the sewage spill reports to Georgia EPD. More than 750 thousand gallons of sewage is reported overflowing from manholes in Dekalb County, with several more reports of unknown quantities that we have not included in the total. The March of sewage from Dekalb County splits off along the height-of-land divide. On the north side, sewage and stormwater head to the Chattahoochee River in the Gulf of Mexico basin. South of the divide, the stormwater overflows carry contaminants through the Atlantic Ocean drainage basin via Lake Jackson and the Ocmulgee River.
Ocmulgee River originates at Lake Jackson, flows past Jackson and on down to Macon where it first overran the channel on Thursday March 6, just after school final bell and ahead of the evening commute.
Downstream from Macon, the Ocmulgee began to swell with flood flow, spilling over at US-341 at Hawkinsville in the wee hours of March 9, having doubled its depth in the channel at US341 in just over 24 hours. The floodwater bolus pushed further down and over the channel near Abbeville around 10 pm March 10, 15 and a half hours time lapsed between the two. Ocmulgee initially behaved on the passing through Lumber City, sticking in its channel on its way to rendezvous with Oconee River, the twins teaming up to flood next near Baxley.
Oconee River started flooding March 6 around 7pm. USGS provisional data recorded the first channel breach at the monitoring station in the upper Oconee River watershed near Penfield. Downstream at Milledgeville the monitors lit up for extreme high flow however, the channel held and did not breach, containing Oconee River flow through the whole March event. Downstream at Avant Mine, flood stage was breached March 8 around 8 am, a 36 hour lapse from the first overflow at Penfield. In less than 19 hours following, flooding began near Oconee, this one coming on March 9 at around 230 am. Dropping further downstream to Dublin, flooding started up on a 52 hour delay, beginning March 11 around the morning commute, 7 am. Another day forward, March 12 around 8 pm, Oconee broke out of the channel at Mount Vernon, 37 hours lapsed from flooding recorded on the upstream monitoring station.
Oconee River gradually stopped flooding in the same order that it started, with Mount Vernon being the last station to quit, Sunday afternoon on March 17, ending 11 days of flooding. Ocmulgee River continues to flood near Abbeville, the last monitored location ahead of the confluence with Oconee, the genesis of Altamaha River.
Flooding initially began at the second monitoring station of the Altamaha near Baxley where the channel is just below 13 ft deep. The breach near Baxley occurred March 9 right before the lunch hour. Twenty-five hours later, Altamaha was flooding upstream at the first monitoring station, installed near Charlotteville. Altamaha flooded near Charlotteville and Baxley four full days before flood hit downstream at Doctortown, March 13 around the evening commute, 5pm. Another time lapse two and a half days forward, around 230 am March 16, flooding began at Everett City.
The blackwater river Ohoopee began flooding near Reidsville the afternoon of March 7, depositing more than 3000 cubic feet per second into the over-full Altamaha system between Baxley and Doctortown. Ohoopee ran over flood stage for nearly two weeks in March, finally returning inside the channel mid-morning on March 20. Not to be outdone or forgotten, Ohoopee rose up again and overflowed on March 25, still rising on Day 21. Flooding on the Ohoopee River receded into the channel on April 2. After the rains of April 11, Ohoopee River breached flood stage a third time near Reidsville, coming out of the channel on April 13 around 5 am. As of this report Day 40, Ohoopee is still actively flooding, appears to be leveling off, may have reached peak flow.
The beginning of the end
Altamaha River flow volume started to taper off on March 21, first noted in the upper end near Charlotteville. The glut of flood flow had passed by the first monitor and made its way downstream, flooding all the way to Everett City near the outlet at the Atlantic Ocean near Brunswick. As of Saturday, March 23, the flow volume at the top end was down under 30 thousand cubic feet per second, still more than double, over 60 thousand cfs at the lower end. The depth of flow above flood stage as of Saturday March 23 ranged from half a foot over at the top end of Altamaha to three feet over flood stage downstream, the monitors near Charlotteville, Baxley, at Doctortown and Everett City gradually receding with no further encouragement from flooding tributaries.
Altamaha River flood finally receded beneath flood stage near Charlotteville around 9 pm on flood event Day 17, March 23. By Day 18 mid-morning, Altamaha flooding was over at Doctortown. As the Ohoopee River kicked up a flood fuss again on March 25, Altamaha River continued to recede, ending the overflow at the bottom end near Everett City over the noon hour on the 20th day, March 26. Altamaha River stopped flooding near Baxley on April 4 and was quietly contained in her channel for ten days. The rains of April 11 did not provoke her instantly, it was on Day 39 Altamaha rose up again, April 14. Altamaha River flows four inches over flood stage at Baxley as of this update.
Savannah River flooding initially broke out near lower end Cylo around 5 pm on March 10. Flooding progressed backward on the Savannah River, spilling out upstream at Burtons Ferry Road near Millhaven a little more than two days later. As seen with Altamaha flood progression, the channel depth may have something to do with the order of flood breach. Minor flood stage near Cylo is 11 ft, where upstream near Millhaven the channel is 15 ft deep. The time lapse between the two breaches, downstream to upstream, 52 hours.
Savannah River flooding, like the Altamaha described above, ended on April 4. The calm did not last as long, it took a week for Savannah to crash her gates and flood again near Cylo, rising right around the same time that Satilla was provoked to turn from her declining trend to rise and spill further out of the channel. Savannah River flooding ended near Cylo on April 18 around 915 pm.
Satilla River began to flood at GA158 near Waycross on Day 18, the afternoon of March 24. Flooding here subsided in the wee hours of March 27 and stayed quietly contained for two weeks before getting out again on April 11. This station finally stopped flooding the afternoon of April 17. Satilla tributary Alabaha River first got out of the channel at GA 203 near Blackshear the afternoon of March 23, flooding less than 48 hours in total. As other channels in the south, Alabaha jumped out of her place near Blackshear during the April 11 rains. Little Satilla River kicked up flooding near Offerman for the third round during the spring floods, initally overflowing flood stage on Day 5 and flooding for a week straight. The channel near Offerman breached a second time, flooding from March 23 to April 5. April 11 rains sparked a resurgence of flooding near Offerman. On April 15, Day 40, Little Satilla was still bucking outside the channel near Offerman, nearly two feet over flood stage and running wild with Satilla and sister Alabaha River. Alabaha River flooding was the first of the triad to quit at GA 203 near Blackshear April 16. The flow near Offerman calmed and rested away into the channel on April 19 during the noon hour. Satilla River continued on spilling out around Atkinson KOA campground until the bitter end, the last flood station to retire, April 25 around 6 pm.
Gulf of Mexico basin
On the Gulf of Mexico side of Georgia's height-of-land-divide, the Chattahoochee and Flint Rivers gather up the runoff from over 16,000 square miles, mustering at Lake Seminole, the impoundment water body created by the Jim Woodruff Dam. Water released from this dam at the Florida border is called the Apalachicola River, escorting Georgia surface water runoff across Florida and into the Gulf of Mexico.
The glut of rainstorm runoff moved quickly out of the top end creeks and streams in the headwater basins into the Flint and Chattahoochee River channels during the March flood event. Chattahoochee River started flooding in Atlanta the morning of March 6. A day-shift later the same day, Flint River started flooding. The first breach came close to the headwaters near Lovejoy, just after 6pm March 6, followed by flooding at Woolsey six hours later, just past midnight March 7. Griffin came next, flooding just after the noon hour on March 7, approximately twelve hours lapsed from the upstream flood.
With excess water building in impoundments upstream, flows released from the dams caused Chattahoochee River to flood at 14th St in Columbus around 11 pm March 8. This is a two and half day delay from the first Chattahoochee overflow noted in Atlanta. Chattahoochee flooding struck downstream Walter F George Dam near Fort Gaines on March 9th just before 5 pm, an 18 hour lag between stations. By March 12 at midnight, flooding was recorded near Columbia, Alabama, after more than three days delay.
Flint River flood progressed in tandem to the Chattahoochee. From Griffin, the flood-flow skipped past Thomaston and spilled out at US-19 near Carsonville in the wee hours of March 9, a 36 hour lapse from the start of upstream flooding at Griffin. Count forward another 24 hours, Flint was backed up overflowing at upstream Thomaston, a brief event ending 11 hours later. Flint River carried on past the flooding US-19 near Carsonville, running high past Montezuma and Oakfield to strike Albany in the wee hours of March 12. Next to flood 18 hours later, Bainbridge on March 12 at 6 pm. Back upstream, the flood caught Newton in the wee hours of Mar 13, a 24 hour delay since Albany started to flood. Later that day, just past the noon hour March 13, Flint was flooding at Riverview Plantation near Hopeful, a little over 12 hours time lapsed from the Newton flood.
From Lake Seminole, the impoundment of the Chattahoochee and Flint Rivers, also fed by a flooding Spring Creek, water released from Jim Woodruff Dam set the Apalachicola River into flood stage By March 10 at 7 pm. Flooding of the Apalachicola River got up over 100,000 cubic feet per second, ending just before noon on March 15. The flood timeline of Apalachicola River extended almost five days. Flint River took the longest time to subside beneath flood stage, the event ending at Bainbridge at 9 am March 21. Another round of flooding started up in the Line Creek tributary at Senoia, on into Flint River, flood stage breached at Lovejoy April 3-4. No subsequent flooding occurred on Flint River downstream of Lovejoy, none of the other tributaries got out of line until the April 11 rains.
When the April resurgence of flooding hit the Gulf basin side of the Georgia divide, the first to spill was Spring Creek, touching flood stage at US27 near Colquitt the morning of April 12. Twelve hours later, Spring Creek got up out of the channel downstream near Iron City the night of April 12, overflowing for a day and a half before tucking back inside the channel.
Ochlockonee River was quiet through the initial spring flooding, unaffected by the surface water coming down from the north. The rains of April 11 landed right on the 1000 square miles of surface area drained by the Ochlockonee River. The first channel breach was recorded at around 9 pm April 11 at GA188 near Coolidge. Less than four hours later, Ochlockonee was out near Thomasville. It took twelve hours for the floodwaters to reach downstream Concord, FL, taking 24 hours to breach moderate flood stage. The flooding near Coolidge peaked twelve hours in, ending April 14 around 7am. Flooding near Thomasville lasted over three days in all. Flooding near Concord peaked on Day 39, is still flooding Day 40, running three feet over flood stage in a declining trend at this update.
Suwannee River tributaries in the south were also set to flooding by the April 11 rains. Withlacoochee River was first to get out of line, breaching flood stage the afternoon of April 11. Alapaha River was next, flooding later afternoon on the 11th of April near Jennings, FL. Tributary Little River breached flood stage near Adel around noon on April 12. It took 12 hours for floodwater to move down the Withlachoochee River channel to reach the downstream monitor at US84 near Quitman. It took two more days for Withlacoochee to spill over downstream near Pinetta, FL. Around this time, Suwannee River breached flood stage at US441 near Fargo. Little River flooding progressed to the next station downstream at GA122 near Hahira after a 40 hour delay and was all over by Day 40 in the early morning. Withlacoochee River was still flooding at all three monitoring locations on Flood Day 40. Alapaha River flooding progressed in reverse, going upstream to Statenville 40 hours after the breach near Jennings. By Day 40, Alapaha River peaked in moderate flood stage at Statenville and Jennings with a high flow is registering near Alapaha. The end of flooding came initially at Statenville, 815 am on April 24, followed by downstream station near Jennings, FL 630 am April 25.
Withlacoochee River got back inside the channel at Skipper Bridge Road near Bemiss in the early morning hours of April 17. Flooding wrapped up at US 84 near Quitman just after the noon hour on April 19th and near Pinetta, FL the last of the flooding cleared up the afternoon of April 21.
Bearing in mind all the creekbank erosion and spills that are carried along with normal streamflow, the fast and furious flood events mix up sediment with a cocktail of who-knows-what, presenting a greater challenge for drinking water treatment plants. Upstream land use is a subject of interest for the mitigation of flood effects, as the surface area can be conditioned to infiltrate rainwater more effectively. Soil carbon holds four times its weight in water, and soil can be amended with time to increase stable carbon. United Nations Intergovernmental Panel on Climate Change suggests that the amendment of soils to increase carbon could capture and hold more rainfall from the increasingly heavy atmospheric river rain events, preventing the rush of surface water runoff to the rivers. More on this as we investigate climate mitigation.
USGS Provisional Data Statement
Data are provisional and subject to revision until they have been thoroughly reviewed and received final approval. Current condition data relayed by satellite or other telemetry are automatically screened to not display improbable values until they can be verified.
Provisional data may be inaccurate due to instrument malfunctions or physical changes at the measurement site. Subsequent review based on field inspections and measurements may result in significant revisions to the data.
Data users are cautioned to consider carefully the provisional nature of the information before using it for decisions that concern personal or public safety or the conduct of business that involves substantial monetary or operational consequences. Information concerning the accuracy and appropriate uses of these data or concerning other hydrologic data may be obtained from the USGS.
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