Between midnight and 10:00 am CDT on Saturday, August 21, 2021, very heavy rainfall resulted in widespread flash flooding across western Middle Tennessee, including the town of Waverly. During the event, much of a five-county area received up to a quarter of normal annual rainfall in under twelve hours, as much as 10 to 15 inches (250 to 380 mm).[5] In a situation described as catastrophic,[6] Waverly was severely damaged by floodwater, with hundreds of homes and dozens of businesses destroyed and swept away.[7] Numerous people became trapped, leading to widespread water rescues. The event resulted in 19 fatalities in Waverly, with another in nearby Hurricane Mills,[4][8] and is regarded as one of the worst natural disasters in Tennessee history. The event broke the 24-hour rainfall record in Tennessee, with over 20 inches (510 mm) of rain falling in McEwen.[9] Flooding also occurred in parts of western Kentucky, but to a much lesser extent.[4]
A stalled frontal boundary west of Nashville led to training thunderstorms during the early hours of August 21, producing very heavy rainfall rates across the counties of Stewart, Houston, Dickson, Humphreys, and Hickman. Precipitable water values reached as high as 2.37 inches (60 mm) at 7:00 a.m. CDT, besting the previous record of 2.21 inches (56 mm) for that specific date and time.[10] Rain started shortly after midnight and intensified throughout the morning, quickly filling area creeks and streams. By daybreak, numerous homes and businesses had been flooded in Humphreys County, leading to evacuations and water rescues. A rain gauge operated by the Tennessee Valley Authority in McEwen recorded 17.02 inches (432 mm) of rain, setting a provisional daily rainfall record in Tennessee.[11] This broke the previous record of 13.6 inches (350 mm) recorded in Milan in 1982. The previous highest daily record rainfall in Middle Tennessee was 9.45 inches (240 mm) in Franklin in May 2010, and the two-day total for Nashville in 2010 was 13.57 inches (345 mm). Months later, in December, another rain gauge in McEwen, located at the McEwen Wastewater Treatment Plant, was officially verified as the state record, having recorded 20.73 inches (527 mm) of rain, breaking the previous record by slightly over 7 inches (180 mm).[9]
Eastern Humphreys County, around the McEwen area, received substantially more rainfall than Waverly. However, the headwaters of Trace Creek originate in eastern parts of the county, with all the water draining westward through Waverly. Areas of Houston, central Humphreys, and northern Hickman counties still received upwards of 8 to 10 inches (200 to 250 mm) of rain during the event.[12] The historic rainfall totals in McEwen and resulting flooding event in Waverly were compounded by a 300-foot (91 m) drop in elevation along Trace Creek as it flows westward into Waverly,[10] along with a CSX Bruceton Subdivision railroad bridge adjacent to U.S. Route 70–roughly one mile (1.6 km) east of town–that became blocked by debris, resulting in a temporary dam and lake forming. The land under the railroad eventually gave way, sending a large tsunami-like wave into Waverly, with much of the town becoming inundated within the following five to twenty minutes.[13][14]
A level three state of emergency was declared by the Tennessee Emergency Management Agency (TEMA) for Dickson, Hickman, Houston, and Humphreys counties in response to the flooding event.[8][15] As many as 4,200 customers were left without power by that afternoon, 3,500 of which were in Humphreys County.[11] According to TEMA, over 700 homes were flooded during the event, mostly in Waverly.[16]