Rain has ended in the Mississippi Valley, but the damage has been done. Communities along the Mississippi River and its tributaries in Missouri, Illinois, and Arkansas, remain submerged by floodwaters that will take several days to recede.

The Mississippi River near Cape Girardeau, Mo., is expected to peak within a few inches of a record crest this weekend. Upstream in St. Louis, the forecast crest of 42 feet would be one of the five highest on record. At least 10 points along Missouri’s rivers have also seen record crests in the last few days.

Parts of Interstate 55 in Missouri were closed from the flooding, and there were more than 100 reported water rescues.

The flooding has been driven by several rounds of intense rain over the past week.

7-day rain totals ending May 4, 2017

7-day rain totals ending May 4, 2017.

Credit:

At least five inches of rain have fallen over half of Missouri in the past week, with some areas getting more than 10 inches. The town of Houston, Mo., was deluged with 11.15 inches of rain in less than three days.

Swollen rivers have become more common. In the long history of the Mississippi River in St. Louis, four of the eight highest crests have come since 1993.

 


Flooding around Pocahontas, Ark., and other parts of Arkansas and Missouri can be seen in these before-and-after satellite images.
Credit: NASA Earth Observatory

 

The most recent National Climate Assessment indicates that heavy precipitation has increased 37 percent in the Midwest, which includes Missouri.

A Climate Central analysis, updated through 2016, also found that the frequency of heavy rain is increasing in Missouri and the vast majority of other states in the U.S. The analysis examined the heaviest 1 percent of daily rainfall at more than 3,000 gauges across the U.S. and found that these extreme events are happening more often. Missouri and Iowa are two of the states that have the greatest increase, more than 80 percent since 1950.

In a world warming from increasing greenhouse gases, evaporation from oceans, lakes and soils also increases. For every 1°F (1.8°C) of warming, the atmosphere can effectively hold 4 percent more water vapor. This additional water vapor increases the odds of heavier rain.

Increase in heavy rain across Missouri

Increase in heavy rain across Missouri 

Slow-moving weather systems are another factor in heavy precipitation, as a slower-moving system can produce more rain over particular area. There is some evidence that a warming world will affect jet stream patterns, which control the speed and direction of weather systems.

While floods have always been a part of life along the Mississippi, these changes to the atmosphere, as well as changing land-use, such as channel narrowing, will likely raise the risk of devastating flooding to the Mississippi Valley in the future.