Multiple rivers in Missouri, Illinois and Kentucky are finally cresting after several days of record flooding that began in the final days of 2015 and has spilled over into the new year. The flood waters have damaged or destroyed thousands of homes and businesses and left more than two dozen people dead, with many more forced to evacuate.
An unusually strong and persistent winter storm pounded the central U.S. with rain and wintry precipitation for three days starting on December 26th. By December 28th, a wide swath of Missouri and Illinois had picked up at least three inches of rain, with 6-12 inch totals extending along the I-44 corridor (see Fig. 1). According to the National Weather Service, the three day rain total of 9.80 inches in St. Louis was more than enough to push 2015 to the top of the record books as the wettest year on record for the city with 61.24 inches of water (the previous record was 57.96 inches in 2008). It was by far the wettest December ever recorded in St. Louis with 11.74 inches of rain, blowing past the old record of 7.82 inches in December 1982.
Even as the rains diminished on December 28th, the widespread flood disaster was only beginning as heavy runoff quickly made its way from creeks into smaller tributary rivers and eventually the main arteries. Both the Missouri and Mississippi Rivers reached major flood stage rapidly, including in St. Louis, where the Mississippi crested at 42.58 feet, the third highest crest ever measured there. Fortunately the city itself was mostly spared by a robust levee system and favorable topography.
That has not been the case for places south of St. Louis. The Mississippi River reached levels never before seen in the town of Cape Girardeau, Missouri on New Year’s Day, rising to 48.86 feet, breaking the record set in 1993 during one
of the worst flooding events in U.S. history. But the worst of the flooding happened in the southern suburbs of St. Louis. The Meramec River saw water levels approach or set new records in several locations, including the Missouri towns of Pacific, Eureka, Valley Park (see Fig. 2) and Arnold. Thousands of homes and businesses in these towns were either damaged or swept away, according to the Associated Press. The high waters also forced the prolonged closure of two major interstates, snarling holiday traffic.
The AP also reports there have been at least 31 deaths as a result of the flooding in the past week, with most of those killed in cars swept away by the high waters. On average, more people are killed by flooding each year in the U.S. than by tornadoes, hurricanes or lightning, so it’s imperative to use extreme caution during flood events, whether it’s river flooding or flash flooding caused by thunderstorms. While the worst is now over for central Missouri, the water will continue to flow south, likely forcing the Mississippi River to overflow its banks for the next several days in Arkansas, Tennessee, Mississippi and Louisiana. It may be the second half of January before the flood risk completely subsides.
The severe flooding and record warmth of December in the US can be at least partially blamed on the current El Nino, one of the strongest on record. The same pattern has caused torrential rainfall over portions of central South America leading to the worst river flooding there in 90 years. The Uruguay River at Concordia, Argentina, rose more than 45 feet above flood stage, requiring the evacuation of at least 160,000 mostly poverty-stricken residents and at least 30 deaths.