The Van Trump Report

“Well Above Normal” Flood Risk for Mississippi River This Spring

An enormous amount of snow fell across the northern plains this year and as the weather warms, the resulting water is going to be looking for a place to go. While the US National Weather Service (NWS) recently lowered the risks of major flooding from the snowmelt, the risk remains nonetheless. 

Based on snowmelt alone – meaning not accounting for any additional rainfall – NWS expects the Mississippi to reach river levels similar to those seen in April 2019, which ended up reaching the second highest stage on record. The good news is that NWS doesn’t see Mississippi flooding lasting as long as it did in 2019 when many locations were at or above flood stage for 9 whole months. 

The cause of flooding in 2019 was the result of a series of high precipitation events. First, the 2018-2019 winter was the wettest on record. Winter precipitation ranked in the top 10 out of 124 years in 15 states within the Mississippi River Basin. Above-normal precipitation continued into the spring, which ranked as the fifth wettest on record. For the 12-month period ending in June, precipitation totaled 37.93 inches. That was also the third month in a row to set a new 12-month precipitation record!

The 2019 Mississippi River flood caused a negative economic impact of more than $20 billion across 29 states in the Missouri, Arkansas, and Mississippi watersheds. The duration of flooding at Greenville, Mississippi, and Red River Landing and Baton Rouge, Louisiana, exceeded the records set by the Great Mississippi Flood of 1927. In addition to property and crop losses and infrastructure damages, commercial navigation on the Mississippi River was interrupted repeatedly by high currents, low bridge clearances, and closed locks. This delayed shipments of agricultural commodities, adding to the economic stress of crop losses caused by flooding.

So far this spring, NWS says that abnormally dry soils have absorbed a “copious amount” of snow melt, which has decreased the risks of severe flooding. Still, according to the National Weather Service in Duluth, MN, “A near record amount of water stored in the snowpack will be released.” But even though the overall risk of spring flooding is well above average on the Mississippi River, NOAA notes that this does not guarantee high impact flooding will occur.

Additional precipitation events and the rate of snowmelt in the upper Mississippi basin will be the main factors determining the severity of the flooding this spring. A rapid snowmelt occurring over still frozen ground would increase the likelihood of high impact flooding on the Mississippi River this spring. A slow, steady melt would decrease that threat.  The main stem of the Mississippi River is projected to crest in Iowa toward the end of April and the beginning of May.

AccuWeather Meteorologist Matt Benz warns that because of the large volume of water the Mississippi River handles, it can take many weeks for waters to rise, crest and fall. While there are some locks and dams along the upper portion of the Mississippi, they are unlikely to prevent moderate flooding later this month and into May. Major flooding – short of record high levels – is possible, especially if large precipitation events develop. If substantial rainfall across much of the upper Mississippi watershed is avoided, then major flooding may be avoided in most locations, AccuWeather forecasters say.

NWS officials warn that if you have interest along the river, the time to prepare for flooding is NOW. For crops, experts suggest opening all drainage ditches and removing any debris from fields and pastures that could injure plants or damage machinery. Producers should also make a list of their farm inventory, including all livestock, crops, machinery and equipment, and hazardous substances, including pesticides, fertilizers, fuels, and others. Iowa State University has some handy checklists that farmers can use to make plans before, during, and after a flood situation HERE. (Sources: NWS, USGS, AccuWeather, Iowa State)

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