Field crews measure record flooding along Mississippi, Ohio Rivers

Field crews with the U.S. Geological Survey (USGS) are measuring record flooding on rivers and streams in 12 states across the country, with more than 50 preliminary record-high flood measurements along the Mississippi and Ohio Rivers and their tributaries.

The USGS said in a statement earlier this week that it is making preparations for a “prolonged field effort” along the two rivers as major flooding will extend “well into mid-to-late January,” particularly along the lower Mississippi River.

Currently, Missouri, Arkansas and Illinois are experiencing the most extreme flooding. Flooding in Missouri has caused 22 fatalities, hundreds of road closures and more than 1,000 power outages across the southern portion of the state, USGS reported.

Jeff Waters, manager, model product strategy at Risk Management Solutions, Inc. (RMS), said in a statement that this event will likely trigger residential and commercial flood policies along the impacted rivers. “However, the most heavily impacted states (Mississippi, Missouri, Illinois, and Arkansas) have just over 155,000 National Flood Insurance Program policies in place combined, meaning that much of the residential losses are unlikely to be covered by insurance,” he said.

AIR Worldwide, a catastrophe modelling firm, said on Thursday that “a gradual realignment of the large-scale pattern over North America caused widespread storminess, including flooding rains, severe thunderstorms and tornadoes, across most of the Midwest during the Christmas week.” The storm brought heavy rains to eastern Oklahoma, northwest Arkansas, and southwest Missouri, with 10 inches falling in a 30-hour period ending Dec. 27, 2015, on the south side of Springfield, Missouri, AIR said in a press release.

During this particular storm event, two sewage treatment plants and a drinking water plant in Missouri were inundated by water and failed, contributing untreated sewage to the floodwaters, the USGS statement added.

Many have compared the Midwest winter floods of December 2015 and January 2016 to the floods of 1993 and 2011, AIR said. In 1993, the most severe flooding was concentrated along a 500-mile stretch of the Mississippi River between Cairo, Illinois, and Minneapolis, Minnesota, and along a 400-mile length of the Missouri River from Omaha, Nebraska, to St. Louis, Missouri. Overall economic damage estimates exceeded US$15 billion (in 1993 dollars), by far the greatest flood loss in U.S. history, with one-third of the damage to agriculture, the release noted.

Although the 2011 flood was shorter in duration, lasting from April to May, flood levels were higher in some locations. The economic damage was a few billion in 2011 dollars.

“In contrast, floodwaters for the current situation have risen and fallen relatively quickly – primarily because the intense precipitation occurred over a short period of time and covered a relatively small region,” explained Dr. Hemant Chowdhary, principal scientist at AIR Worldwide.

“Floodwaters are already receding in some parts of Missouri and Illinois, but not without having set records in some towns, such as Cape Girardeau and Thebes, Missouri,” he said. “At Thebes, the Mississippi crested at 47.74 feet on Jan. 2, the highest level ever observed; the crests in May 2011 and Aug. 1993 at this gauge were 45.52 and 45.51 feet, respectively. At Cape Girardeau, the river reached 48.86 feet, surpassing the previous record of 48.49 feet set in Aug. 1993.”

Missouri Governor Jay Nixon requested a federal emergency declaration to speed debris removal and efforts to clear what is estimated to be as much as 500,000 tons of debris are underway, AIR said. On the evening of Jan. 5, Nixon estimated that more than 7,000 structures in the St. Louis region were damaged by flooding. In St. Louis County, 900 homes and businesses were damaged, according to officials.

The Governor of Illinois, Bruce Rauner, has issued a disaster declaration for 23 counties, AIR reported, noting that there are eight river gauges still at major flood stage in Illinois. In addition, the Mississippi broke through a levee in Thebes, on Jan. 2, flooding areas as far as six miles inland.

The U.S. Army Corps of Engineers also began daily inspections of Mississippi River levees in Louisiana on Thursday. These inspections will continue through the beginning of February, as the river is forecast to be at the official flood stage of 17 feet through Feb. 3.

According to AIR, since 1993 there has been a great reduction of exposures within and near the floodplains of the Mississippi, Missouri and Illinois rivers in the areas that were hit the worst during both the 1993 floods and the current event in the states of Missouri and Illinois. In addition, many of the levees that failed in 1993 were rebuilt to withstand an event similar to the 1993 flood, and some of the remaining properties on the floodplains were flood-proofed to “some degree.”

Waters added that although flood risk in the U.S. is primarily driven by tropical cyclone-related events, “this event highlights the material risk posed by non-tropical cyclone precipitation as well. It also stresses the importance of having undefended views of flood hazard alongside defended views, especially considering that nearly a dozen levees have been breached to date.”