Streamflow and Flooding
Since 1912, the stream gauge on Peachtree Creek (AANG1) has been located where it crosses Northside Drive just east of Interstate 75, just northwest of the Brookwood Split (where Interstate 85 leaves 75). It is located at 33°49′10″N 84°24′28″W / 33.81944°N 84.40778°W / 33.81944; -84.40778 (Peachtree Creek, USGS stream gauge AANG1 at Northside Drive)Coordinates: 33°49′10″N 84°24′28″W / 33.81944°N 84.40778°W / 33.81944; -84.40778 (Peachtree Creek, USGS stream gauge AANG1 at Northside Drive), at 764 feet (233 m) above mean sea level. A 1-inch (25 mm) rainfall puts approximately 1.5 billion gallons or almost 6 billion liters into the watershed, by USGS calculations. That watershed (above the gauge only) is 86.8 square miles (225 km2). There is also water quality monitoring equipment there, all transmitted to GOES weather satellites and back down to the USGS in real time. Prior to this current system, daily flow and water quality sampling were done as far back as 1958 and 1959, respectively. Records for this site are maintained by the USGS Georgia Water Science Center.
Flood stage is 17.0 feet (5.2 m) depth, and due to the heavy urbanization in the area, it often reaches above this mark during heavy storms. Peachtree Creek suffered massive flooding after Hurricane Frances and Hurricane Ivan in September 2004. Late on September 16, 2004, it reached a stage of 22.63 feet (6.90 m), a flow of 14,200 cubic feet (106,223 gallons) or 402 cubic meters (402,100 liters) per second, and a width of 450 feet (140 m), its highest official flood record ever, which actually washed away its gauge. The creek was about ten times its normal width, three times its normal speed, and 300 times its normal flow.
The worst flood ever occurred in 1919, when on January 29 (1/29) or December 9 (12/9) it reached a flow of about 21,000 cubic feet (160,000 gallons) or 600 cubic meters (600,000 liters) per second, and a stage of 25.80 feet (7.86 m). Another flood occurred in 1912 just above the 2004 event, and another in 1915 just below it. (Prior to the 1940s, there are no records for depth.) Base flow for the stream is about 67 cubic feet (1.9 m3) per second, and a depth of about 3 feet (0.9 m).
The 2009 Atlanta floods set new records for most streams in the area, and Peachtree Creek at Northside Drive came a close second place, reaching a height of 23.89 feet (7.28 m) on September 21, 2009 at 9:15 pm, and causing water to flow over the bridge. The North Fork reached a record of 18.07 feet (5.51 m) at 7:15pm, topping the previous record of 17.70 feet (5.39 m) in September 2004. The South Fork reached its third-highest ever at 15.21 feet (4.64 m) 5:45pm, the record being a flood that brought it to 16.35 feet (4.98 m) on March 16, 1976.
The other stream gauges are SPJG1 on the South Fork "near Atlanta" at Johnson Road since April 2003, and NPBG1 also "near Atlanta" on the North Fork at Buford Highway since May 2003, with another (NFPG1) on the North Fork further up "near Doraville" at Graves Road since June 2001.
Read more about this topic: Peachtree Creek