Fact Sheet - Record Six Hour Rainfall in Kentucky
On June 23rd, 1969, a swath through South Central Kentucky and North Central Tennessee experienced devastating amounts of rainfall. A line of thunderstorms was responsible for the record-breaking rainfall. In a period of six hours beginning at 2:00 a.m.,Scottsville in Allen County, Kentucky received 8.34 inches. That was a record-breaking amount for that time period and the record still stands today (1). Red Boiling Springs in Macon County, Tennessee was severely damaged by flood waters produced by the same storm. An unofficial report claimed nearly ten inches of water fell in the watershed of Salt Lick Creek within a six hour period (2).
This record-breaking storm event was analyzed by looking at various resources such as newspaper accounts of the flash flood, surface and radar weather observations provided by the National Climatic Data Center, and by the surface analysis charts for June 23rd, 1969 also sent by them. This information was used to determine the cause of the storm, its impacts on the communities, and the probability of a flood of this magnitude occurring again.
In Allen County, Kentucky, Trammel Creek flooded so severely that it claimed three lives, damaged 100 homes, and rain damaged 50% of all crops in Allen County (2). The total damage in the county, combining both public and private property, came to 28.5 million dollars (3). In Red Boiling Springs, Tennessee, Salt Lick Creek caused death and destruction when it flooded. Two young children drowned and flooding caused approximately two million dollars in damage in the once tourism town (2).
From the midnight surface analysis on June 23rd, 1969 a cold front to the west is bearing down on Kentucky (4). A warm front well to Kentucky's north has already moved through the area bringing, warm, moist air from the Gulf that created a warm sector between the warm and cold fronts. Two low-pressure systems are located on the map and a wave cyclone has developed. A wave pattern denotes movements of energy along boundary lines. You can see this pattern by looking at frontal boundaries and the crimps or waves in the isobars, lines connecting points of equal pressure.
The 3:00 a.m. surface analysis chart shows that the low-pressure systems have moved slightly to the southeast (4). The cold front has moved slightly to the southeast. This appears to be a slow moving system which means that the rain will not advance quickly which could produce localized flooding. Thunderstorms have already begun in Bowling Green at this time. Nashville Radar Observations have picked up a line of thunderstorms in the region (5).
The lines show little movement as plotted by the Nashville Radar reports. They remain over the same area, allowing for the vast flooding, but the lines do change shape. The center point of the line moved only 15 miles north to south over the six hour period. Note the lines are in an alternating "V" pattern from hour to hour. Alternating troughs and crests are consistent with a movement of a wave from the west to the east.
The 6:00 a.m. surface analysis chart has a very important feature on it (4). A squall line is basically directly over the flood region in South Central Kentucky and North Central Tennessee. A squall line is a band of intense, localized thunderstorm activity.Hourly precipitation data from Scottsville, Kentucky station shows that between 4:00 a.m. and 5:00 a.m. 2.24 inches of rain fell making this the peak rainfall interval (1). This drained a lot of moisture from the system, therefore rain amounts decreased from this point on.
Hourly precipitation data from Scottsville, Kentucky station shows that between 4:00 a.m. and 5:00 a.m. 2.24 inches of rain fell making this the peak rainfall interval (1). This drained a lot of moisture from the system, therefore rain amounts decreased from this point on.
From the cumulative rainfall data one can see the progression of water going into the streams in the flood region. Trammel Creek, in Allen County, split a home in half near Adolphus, where three of the four individuals inside the home died (6). One body was found six miles downstream from the residence. Also, in Adolphus, a store was ripped from it's foundation and carried at least thirty feet (7). Only a few towns were greatly effected by mass destruction because it was a localized flash flood event.
On the total rainfall distribution map one can see how localized the rains were especially the areas in dark red, which represent where approximately 8 inches fell. The Rainfall Frequency Atlas of the Midwest, states that in our region of the country, 5.97 inches of rain over a six hour period would probably occur once every 100 years (8). Scottsville, Kentucky exceeded that 100 year amount by over 2.3 inches. In fact, the six hour rainfall exceeded the amount expected during 24 hours once each 100 years!
Today better technology, such as Dopplar and NEXRAD radar make accurately forecasting flood events more likely than in the past. Flash flood warnings issued by the National Weather Service now are communicated to each county. In addition, the better technology has led to warning systems such as NOAA weather warning radios which can be purchased for about 30 dollars. The same warnings issued by the National Weather Service can be heard in real time at home; even at 2:00 a.m. in the morning when residents of Scottsville, Kentucky in 1969 were unwarned and still asleep.
United States Department of Commerce. Environmental Sciences Services Administration. (1969).Hourly Precipitation Data Daily Totals. (Vol. 19). Asheville, N.C.
United states Department of Commerce. Environmental Sciences Services Administration. (1969).Storm Data. (Vol.11). Asheville, N.C.
Citizen Times. (1969, June 26). p. A1.
National Climatic Data Center. Surface Analysis Charts. (1969, June 22-23).
National Climatic Data center. Nashville Weather Observations. (1969, June 23).
Search for Victims End. (1969, July 2). Allen County News [KY]. No. 27.
Floods in Kentucky, Tennessee Leave at Least Two Dead. (1969, June 23). Courier-Journal[Louisville, KY]. p. A1.
Huff, F.A., Angel, J.R. (1992). Rainfall Frequency Atlas of the Midwest. Illinois State Water Survey. Champaign, Illinois.