The Mississippi River Flood: How bad could it get?

By now, many Americans are aware of the major flooding of the Mississippi River. The river’s water level is reaching record heights not seen since the 1920s and 30s. How bad is it? This blog post tries to answer this question for the lay reader. In short, it’s very bad.

The news to date has been dominated by the flooding in Memphis, TN, where the nation’s largest river crested at nearly 48 feet on Tuesday, May 10. What does this mean? The level at which the river begins to flow over its bank, but not flood any buildings, is 28 feet. This is called the “action” stage by flood experts. The “flood” stage is the level above which life and property are threatened. At Memphis, the river’s flood stage is 34 feet. We are well beyond this. Damages will be severe.

As the massive river bloats and flows downstream toward the Gulf of Mexico, other cities along the river will face similar fates very soon. Mississippi’s governor is already calling for people to consider evacuating communities along the river. Yesterday at Helena, AR, which is 70 miles to the south of Memphis, the river crested above 56 feet. The following table reveals the severity of expected flooding by showing how high the projected cresting levels are above flood stage and the expected cresting dates at successive downriver points. This is flooding above the official danger level.

Can we predict the damage in terms of dollars? Not yet. Damage data are not yet in for the present flood, and will not be for some time. Flood damage refers to the physical damage of structures and contents, but just as important are the economic losses associated with business interruption and the inability of employees to report to work. The economic recovery process will be longer than the physical recovery, but thankfully, the latter will facilitate the former.

Most media reports are comparing this flood to the famous 1927 flood of the Mississippi River, but life along the river was quite different then. Flood damage is driven largely by the number and types of building and other structures, the value of the internal inventories, and the length of time and quality of water inundation. Today, one will find much more development and population along the river than in 1927, particularly in the cities listed above. Thus, the 1993 flood of the Mississippi River may be more instructive. According to the US Geological Survey, the 1993 flood caused over $20 billion in damages. Unfortunately, we should probably expect damages of similar magnitude, if not greater.

Author: Dr. Lloyd Blanchard, Director of Public Performance Management