The Great Midwestern Flood of 1993

The Fall of 1992 was both cooler than normal and unusually wet.

The Fall of 1992 was, in fact, so wet that soil saturation remained above normal levels well into the Spring of 1993. The cooler than normal temperatures led to decreased evaporation from the soil, which allowed water to saturate the ground more rapidly.

This excess saturation meant that when abnormal Spring-Summer weather patterns caused greater than normal rainfall frequency for longer than normal durations, there was low water retention capacity in the soil which resulted in major flooding across Illinois, as well as North Dakota, South Dakota, Nebraska, Kansas, Minnesota, Iowa, Missouri, and Wisconsin.

During the late Spring of 1993, abnormal patterns began to take place in the large-scale weather features that overlie the Midwestern region.

The semipermanent polar jet stream that serves as a boundary between cool northern air currents and warm southern air currents stalled south of its normal general location. At the same time, constant warm, moist air was shifting north due to the westward movement of a large region of high pressure located off the southeastern coast of the United States.

While these two opposing weather systems generally do not interact, they are not permanently fixed in any single location. In the late Spring and early Summer of 1993, the jet stream caused northern air masses that were substantially colder than seasonally normal to be pushed into the northcentral part of the country, while the high-pressure zone off the coast became entrenched over South Carolina and Georgia, causing a continuous flow of warm moisture that moved northward into the Central Plains.

The alignment of a high-pressure system overlying the east coast and a low-pressure system overlying the central part of country led to heavy and persistent rains over the area. The constant interaction of cool and warm air would result in intense rainfall for the duration of these abnormal weather patterns.

For reasons still debated within meteorological literature, these weather patterns became stationary throughout June and July in 1993.

Heavy rainfall became almost consistent over the Mississippi and Missouri River basins until the first week of August when significant breaks in the weather pattern finally began to take place

During this time, an oversaturated landscape became the norm.

The first levees of the region were initially built between 1879 and 1916 to help transform the seasonal wetlands that once dominated the Upper Midwest into a highly productive, flood free, agricultural landscape. Over time, more levees have been built along the Mississippi and Illinois Rivers, reducing the capacity of the valley to serve as floodwater storage and increasing flood stages along the area's waterways. Many of these levees have been improved over the years to accommodate higher flood stages, with flatter slopes, higher crown elevations, seepage relief wells, and other precautions.

Even still, the levees were not enough to hold back the floodwaters.

Due to the increased rainfall and runoff created by the abnormally wet conditions present leading into the Summer of 1993, the levees of the region began to fail. After nearly three months of being at or above flood stages, the levees in Illinois started to fail in early July. During July and August alone, 17 major levees along the Mississippi and Illinois Rivers were breached.

The elevation of a river and its adjacent floodplain decrease as one moves downstream, allowing the rivers of the region to flow rapidly, much like water flowing down a gently sloped table. If there is a barrier, such as a levee, water will collect behind the barrier until it either spills over or breaks through. Levees along the river on the floodplain are designed as walled-in cells (also known as districts), which divide the area alongside the river into separate sections, one after another, all the way down the river. Smaller rivers and tributaries that originate in nearby higher elevations flow between these cells and drain into the Mississippi River. Each cell or district has levee walls that are the same height from the ground all the way around, making the downstream elevation on the top of the levee wall lower than the upstream elevation on the top of the levee wall. A breach in the upstream part of this wall will cause the cell to fill as water attempts to fill the lower lying areas to an elevation equal with that of the point of the breach, which is often higher than the top of the levee at the downstream end of the cell. Overtopping at the downstream end of the cell and its down cutting erosion and breaching of the levee can cause overtopping of the upstream end of the next cell, much like pouring water into a bowl. This was what happened in 1993. As one levee was overwhelmed, the water would spill over and rush down to the next lower district, threatening other districts further down the river.

On July 7, the first Illinois levee was breached at Pope Creek near Keithsburg, flooding 1,260 acres.

Two days later, the levee of the Lima Lake Drainage District failed, leading the the additional failure of the Hunt Levee and Drainage District, causing the inundation of 28,600 acres.

On the morning of July 12, the Indian Graves Levee broke, flooding 8,000 acres of farmland. The next day, another portion of the same levee broke, flooding an additional 10,000 acres.

On July 15, the Len Small Levee on the Mississippi River broke, flooding roughly 20,000 acres and inundating parts of Miller City.

July 18 saw the break of the Nutwood Levee on the Illinois River near Hardin, inundating 11,000 acres and almost isolating Calhoun County entirely.

The levee protecting Kaskaskia, Illinois followed suit on July 22, flooding the town and 14,000 acres of surrounding farmland.

July 25 also brought the worst levee break of the flooding event. The failure of the Sny Island Levee south of Quincy led to the flooding of about 44,000 acres and prompted major evacuation efforts in surrounding communities.

The end of July and beginning of August brought a new wave of levee breaks as the crest of the Mississippi River moved downstream. On August 1, the Columbia Levee failed, causing more than 13,000 acres of additional flooding in the district directly upstream of the district where Valmeyer, Illinois was located.

Close to midnight that same night, the upstream levee of the district that contained Valmeyer was overtopped, causing the inundation of 43,000 acres across that district and one additional district further downstream. The town of Valmeyer saw so much damage from the flooding that the entire town was moved upland during later rebuilding efforts.

On August 3, the cascade of overtopping of cells was finally brought to an end. To prevent the continued flooding of downstream cells and to lower the potential height of the waters that were now flooding into the Stringtown District, an intentional break was made in the downstream end of the Stringtown levee district. The Corps of Engineers utilized a barge and crane to mechanically dredge the levee as a way to direct the floodwater out of the district instead of allowing floodwater to rise and overtop the levee at the downstream end of the district. During the early hours of August 4, two more sections of the levee were blasted near the initial mechanical dredging. These actions to intentionally breach the Stringtown Levee prevented the flood waters from overtopping levees further down the river and also lowered the maximum potential height of the floodwaters that were entering the Stringtown district. It was roughly this same time that floodwaters began to recede, alleviating the potential threat to remaining levees.

According to the U.S. Army Corps of Engineers, 40 federal levees and 1,043 non-federal levees were overtopped or damaged by floodwaters during the Great Flood, however, only 203 metropolitan levees were considered eligible for repair by the Corps of Engineers. The remaining levees, largely protecting rural communities and farmland, were considered ineligible for Corps of Engineers aid and had to seek aid programs administered by other federal agencies.

The breaching of levees throughout the region dramatically altered the landscape along the river. During the five-month period from April 1993 through the end of August, nearly 48 inches fell in east-central Iowa at weather stations that normally only see 33 inches of precipitation in an entire year. Both the Missouri and Mississippi Rivers set new records that year, with the Missouri River cresting at a record 48.9 feet in Kansas City on July 27, 1993, and the Mississippi River setting a new record with a 49.47 foot crest in St. Louis on August 1, 1993.

The entire Mississippi River basin was impacted, with all or part of nine states being declared Federal disaster areas. Counties within North Dakota, South Dakota, Minnesota, Wisconsin, Nebraska, Iowa, Kansas, Missouri, and Illinois all received some form of Federal aid during the duration of and aftermath of the flooding.

All throughout Illinois during the Summer and Fall of 1993, levee reinforcement and repair efforts were taking place. Valiant sandbagging efforts were made by community members and various emergency response organizations along all three riverways during the duration of the flood.

In the areas where reinforcing the levees wasn't enough to keep floodwaters at bay, the direct and indirect harms of the 1993 flood events were felt for months, sometimes even years, after the immediate effects. The retreat of the water left those who were inundated to contend with the destruction left behind.

Some towns that were completely inundated, like Valmeyer, Illinois, faced such devastation that communities were left to make difficult choices about the costs and practicalities of rebuilding.

When the flood waters receded in Valmeyer, roughly 90% of properties were deemed damaged beyond repair. Almost immediately after the initial flood event, the Mayor, Dennis Knoblock, began rallying resources in an effort to keep the community together.

That September, Valmeyer residents gathered in a school gymnasium after the flooding and voted to support rebuilding their town, either on higher ground or out of the floodplain entirely.

After an extensive study of a new potential location, the residents of Valmeyer decided to take up the challenge of moving the city 400 ft uphill, in a location two miles to the east of the original town.

To support initial costs, residents began making downpayments on plots of land, while village officials secured the state and federal funding necessary to create "New Valmeyer." The final cost of the land, construction, and new infrastructure was approximately $35 million.

In 2021, Valmeyer had approximately 1,200 residents.

Valmeyer stands as a prime example of successful floodplain relocation and as a reminder of what extreme weather disaster relief can look like when a community can access the resources necessary to make it happen.

Weather and climate experts throughout Illinois worry that the state and its inhabitants have not learned the lessons of the 1993 flood. Despite several large floods occurring in the same areas in the years since 1993, it seems that few projects to improve levees beyond what they were in 1993 have been undertaken. While there have been efforts to move structures off the floodplain, many river communities are still grappling with growing concerns surrounding levees and effective floodplain management.

Illinois and other states in the Midwest have been getting progressively wetter over the last century. Long-term trends indicate increases in total precipitation and in the number of extreme weather events in Illinois, increasing the likelihood of another major flooding event. The number of days with extreme precipitation events has been above average in the Midwest since the 1990s.

The disaster did initiate new flood response measures. A FEMA buyout of heavily impacted land was used to remediate floodplain land to serve as stormwater runoff storage, which has been associated with reduced damage in the flooding events that have occurred since 1993. The floods also highlighted the issue of extreme underinsurance for flood peril in the region, which prompted 1994 changes to flood and crop insurance programs to decrease reliance on relief programs.

Flooding is a frequent and costly disaster, while at the same time being one of the most poorly managed risks. Increasing precipitation, the inability of dam and levee structures to control the 1993 flood, and the failure of socioeconomic safety mechanisms have resulted in fundamental questions about the national policies surrounding floodplain management. The need to improve risk mapping, increase insurance support to floodplain residents, prioritize preliminary analysis of floodplain development, and focus on holistic ecosystem management are all greater than ever.

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