Why Does the Repaired Len Small Levee, Alexander County, Illinois, US Continue to Breach during Major Flooding Events?

One only needs to study the soil and geologic history and location of the ancient Mississippi and Ohio Rivers to understand why Len Small levee if patched will continue to fail. Much of Dogtooth Bend located in Alexander County, Illinois was originally in the ancient Ohio River valley (Figure 1) alluvial sediments north and east of the confluence with the ancient Mississippi River. The ancient Ohio River valley soils underlain by alluvial sediments and have been easily eroded by the re-aligning modern Mississippi River which now travels through the bedrock controlled Thebes Gap (Figure 2) and into the Ancient Ohio river valley. The primary objectives of this paper are: 1) to explain why Len Small levee, Alexander County, Illinois, US will continue to breach during major flooding events if repaired and 2) to develop a new combined raised causeway and levee system which will provide a Mississippi River floodwater bypass, be sustainable, encourage and fund a land use change, restore the degraded highway road beds, protect remaining Dogtooth Bend farmsteads and farmland that have not yet been degraded by past flooding events and provide floodwater storage during major flooding events at the confluence of the Mississippi and Ohio Rivers.


Introduction
Historically, the Mississippi River flowed southwest of the current city of Cape Girardeau, Missouri [1]. However, glacial meltwaters and seismic activities allowed the Mississippi River to cut a channel through the bedrock controlled upland between Thebes, Illinois and Commerce, Missouri approximately 15,000 yr ago [2]. The ancient Mississippi River Valley and Big Swamp (Missouri) then served as a relief valve when the modern Mississippi River was above flood stage. In the late 1880s the Missouri land owners and farmers south of both Commerce and Cape Girardeau built earthen levees ( Figure 1) to block the floodwaters from entering the ancient Mississippi River Valley and the Big Swamp.
In 1905, the Missouri Little River Drainage District (LRDD) was organized to divert the Ozark Plateau runoff water from the Big Swamp so the swamp could be drained, timbered, cleared and farmed. The LRDD diversion channel and embankment diverted the runoff water from the Little River to the Mississippi River south of Cape Girardeau and north of the Thebes Gap. This finally made it possible to drain the swamp, remove the timber from the Big Swamp and clear the land of stumps for agriculture. However, little attention was given to what happened to the diverted runoff water, which after 1915 increased the Mississippi River flow between Cape Girardeau, Missouri and Helena, Arkansas. The additional Ozark Plateau runoff water contributed to the Great Flood of 1927 which breached levees between Cairo, Illinois and the Gulf of Mexico and killed over 800 people. While the primary source of the 1927 floodwaters was the Ohio River valley watershed; however, the runoff from the 400,000 ha Ozark Plateau watershed with shallow to bedrock and steep sloping soils added to the Lower Mississippi River peak height of the 1927 flood. have not yet been degraded and provide floodwater storage during major flooding events at the confluence of the Mississippi and Ohio Rivers.  [4]. Without access to these flooding relief valves the Mississippi River will continue to challenge the federal frontline and local levee and drainage district levees (Figure 3), grounded on outwash and alluvial materials, and other river training structures which have increased the magnitude and frequency of Dogtooth Bend peninsula flooding and contributed to district and farmer levee breaches. The Len Small levee first breached in 1993 after extensive wing dike construction on the adjacent Mississippi River between Commerce, Missouri and Cairo, Illinois. Olson and Morton [1] recommended three alternatives to USACE at a Mississippi River Commission (MRC) public hearing to address the Len Small levee breaching problem. The first alternative was to repair the 2016 Len Small levee breach, the second alternative was to proactively construct a diversion channel or by-pass from mile marker 33 to 15, and the third alternative was to create a new Mississippi River navigation channel where the bypass floodwaters currently flow. None of these options were implemented. Instead a notch dike or barrier was created in front of the 165 m Len Small levee breach. Dogtooth Bend became a floodwater storage area during the floods of the 2016, 2017, 2018 and 2019. The degraded farmland on Dogtooth Bend has for the most part been abandoned as a result of the craters, channels, gullies and extensive sand deposition. The remaining farmsteads have earthen berms to keep the floodwater out. However, the remaining farmers and land owners were trapped in their homes for weeks at a time since 2016 whenever the Mississippi River was above flood stage and the land and roads were covered by floodwaters. Farmland which could be cultivated prior to 2015 is now non-arable. The land use has permanently changed as a result of the decision not to repair the Len Small levee breach in 2016. The landowners remaining on the peninsula are unable to leave without compensation for the damaged land and loss of their livelihoods. We now suggest that the Dogtooth Bend land south and west of the Miller City to Olive Branch road be used for a floodwater bypass and as a Mississippi River floodwater storage area. The existing Miller City road should become a raised causeway, converted into an earthen levee, with a floodway by-pass or diversion created just southwest of the proposed causeway for floodwaters to pass over the Dogtooth peninsula between mile markers 33 to 15 ( Figure 3). Any floodwater overflow could be stored on Dogtooth Bend peninsula, which could become a wetlands, conservation and forestry area and produce marketable timber in future years. Any remaining infrastructure would have to be removed and wells and sewer systems environmentally capped by new managing authority after the purchased by FEMA at a fair market value or leased or enrolled in perpetual programs at negotiated pre-2015 farmland fair market value.

Missouri Drainage District Farmers Block Floodwaters from
During glacial times (15,000 B.C.) the glacial meltwaters and seismic activities centered at New Madrid, Missouri allowed the modern Mississippi River to cut a channel through the bedrock controlled upland ( Figure 2) south of Cape Girardeau and near the town of Thebes, Illinois. The Thebes cutoff shortened the Mississippi River navigation distance to the Gulf of Mexico by 80 km. The ancient Mississippi River valley was approximately 48 km to the west [2] of the current pathway and remained as a relief valve when the river was at flood stage [1]. The floodwaters would enter the higher ancient Mississippi River valley and flowed into the Missouri Big Swamp which drained south via Little River and St. Francis River [3]. The Big Swamp also received runoff water from the Ozark Plateau [5] and the Francois Mountains northwest of Cape Girardeau ( Figure  2). The runoff and floodwaters made it difficult to drain, clear and farm the Big Swamp. Early attempts to drain and cultivate the 400,000 ha Big Swamp failed periodically.
Initially in the late 1880s the farmers in the Ancient Mississippi Valley south of Cape Girardeau, Missouri and south of Commerce, Missouri ( Figure 2) built earthen levees to block floodwaters of the modern Mississippi River from entering the ancient Mississippi River valley which permitted agricultural use of some of the alluvial soils. However, the runoff from the Ozark Plateau and the Francois Mountains was sufficient to maintain the Big Swamp. These earthen levees may have breached or been topped during major flooding events and could have contributed to the Big Swamp.
In 1905 the Little River Drainage District was created. The goals were to divert the Ozark Plateau runoff water ( Figure 4) and to drain the swampland. By 1915 a Little River Diversion channel and levee was built [3] and it diverted the runoff water to the Mississippi River just south of Cape Girardeau and north of the Thebes gap ( Figure 2). Historically this runoff water drained into the Big Swamp, the Little River and the St. Francis River which flowed into the Mississippi River ( Figure 5) near Helena, Arkansas [5]. This division channel resulted in a significant amount of runoff waters entering the Mississippi River over 300 river miles to the north of Helena

Navigation on Mississippi River Compromised
In 2019 the flooding resulted in 6 empty runaway barges ( Figure 10) passing through the Len Small breach ( Figure 6) and knocking down power lines, crossing a road and coming to rest on an irrigation system in a farmer's field. As noted in Olson and Morton [6] the Mississippi River is cutting 5.8 km channel across Dogtooth Bend and trying to cut off 24 km of the current Mississippi River navigation channel (between mile marker 33 and 15) ( Figure 3). To date the barge company has been only able to remove 4 of the barges from the farmer fields. The other two still remained ( Figure 10) in September of 2019. Previous testimony at the Mississippi River Commission public hearings by Drs. Olson and Morton and by Jeff Denny, the Alexander County highway engineer, and 3 year lobbying efforts by the Farm Bureau have failed to get the 2016 Len Small levee breach repaired as more and more Dogtooth Bend farmers are going out of business. However, the runaway barges which traveled through the rock piles, notch dike and Len Small breach indicate that the Mississippi River navigation channel has now been compromised.
Congressman Mike Bost, Illinois 12 th district which includes Alexander County and Dogtooth Bend met with the USACE Under Secretary R.D. James to see if the project, after 3 years, could be moved up on the USACE priority list. Currently the Len Small levee breach repair ranking is low based on flooding criteria and its cost-benefit ratio. Congressman Bost hopes to get the damages to the navigation channel included. Mississippi River navigation requires a stable channel without cross currents for commercial barges. If the existing river channel is not maintained around Dogtooth Bend peninsula the shipping on barges will have to be replaced by trucks which would add to the transportation costs. The criteria change, even if made, will probably not happen until late 2020 and perhaps be part of the next USACE authorization bill.

Impact of the Little River Drainage District Diversion Channel, Embankments and Ditches on Mississippi River between Cape Girardeau, Missouri and Helena, Arkansas
A historical and regional scale perspective of the effects of the LRDD diversion Open Journal of Soil Science

Impact of the LRDD Diversion on Illinois, Missouri and Kentucky Bottomlands
The role of levees and diversions in protecting agriculture lands and the impacts of breaching of Len Small levee on the agricultural land soil resources was stu-Open Journal of Soil Science

Levees and Other Engineering Structures
The Mississippi River basin is controlled and regulated by the river engineering structures including earthen levees [1], locks and dams [7] and wing dikes ( Figure 11) step up dikes (Figure 12) on the main stem, notched dikes [8] and dams on the tributaries. These dams on the Missouri River [9], a Mississippi River tributary, and other river engineering structures have reduced the magnitude of peak floods, increased base discharges, and reduced the seasonal variability of intra-annual discharges of water and sediment. This extensive system of river engineering structures throughout the basin provides protection from intermediate magnitude floods. However, these engineering structures have reduced the overall channel capacity by up to 4 m for the major floods and resulted in 4 m higher peak heights [4]. Levees and other river-engineering structures in the Mississippi River basin have also provided many socioeconomic benefits. These modifications have resulted in year around navigation, hydropower, flood control, bank stabilization and recreation. Unfortunately these structures have also transformed the hydrologic, sediment transport, geomorphic, water-quality and ecologic characteristics of the Mississippi River and its delta.

Battered by Floods the Confluence of the Mississippi River and Ohio River Needs More Water Storage Capacity
Additional temporary water storage capacity (Figure 15)

Road Degradation
The most recent flood in 2019 on the Mississippi River flowed through the unrepaired levees resulting in substantial Alexander County highway destruction.
The remaining roads look like they were degraded by seismic activity or caught in a landslide. The most extensively damaged area (Figure 17) was between Olive Branch and Miller City just south of the entrance Horseshoe Lake. The Open Journal of Soil Science island. This would result in landowners and farmers in the 6000 ha Dogtooth Bend area no longer have road access to their land if the Mississippi River re-aligns naturally. The MRC/USACE and the Len Small Levee and Drainage District are partners in managing the river landscape and need to develop and evaluate alternative strategies for addressing the river-land relationships in the Dogtooth Bend area. Several alternative courses of action were presented. While each alternative needs to be evaluated and negotiated, they offer a start in visioning different scenarios to guide preparation for future [5]: The first alternative is to continue as in the past, to repair the Len Small levee [8]. This could impede and delay the eventual and natural tendency of the Mississippi River to take a shortcut and re-align its downstream course. This alternative is a near-term fix. There is a high likelihood at some future date that another major flood event will occur and the Len Small levee will breach again, Historically, the Mississippi River bottomlands have experienced hundreds of Mississippi River re-alignment events and course changes in the river. The large number of oxbow remnants and interior old meanders (e.g. nearby Horseshoe Lake area) are evidence of the past and harbingers of the future. Federal, state and local managers of the Mississippi and Ohio River landscapes can impede or delay the Mississippi River's natural re-alignment using river training structures but attempts to maintain the current alignment even if the Len Small levee breach was repaired will eventually fail even with these structures. The mighty Mississippi River will eventually win as it always has and time is on the river's side.

Summary and Conclusions
In conclusion, there has been a tendency to underestimate the impact of the If the Cairo floodwall and levee were to fail, it would put nearly 2800 residents and 400 structures at risk. If the Commerce to Birds Point levee, or Hickman levee or the New Madrid floodway front line and setback levees were to fail 800,000 ha in Missouri, Kentucky, Tennessee and Arkansas bottomlands could be flooded with both crops and soils damaged (Figure 15). The opening of the New Madrid Floodway, built between 1928 and 1932, can be used to reduce the pressure and peak height by as much as 0.6 m per day on confluence area levees. The floodway was used in 1937 and 2011. There is a need for additional floodwater storage capacity [5] in the confluence area of the greater Ohio and Mississippi rivers (Figure 15). A regional effort on all sides of the Ohio and Mississippi Rivers is needed to strategically identify floodplain areas that could provide temporary water storage and policy incentives for landowners of low-lying bottomlands to profitably invest in crops and income alternatives. One of the most difficult issues the USACE, state, levee districts and local citizen partner's face is how to reconcile the differential geographic impacts levees and diversion channel have upstream and downstream on land use and flood risk. Leveed systems have allowed agricultural intensification [5] but have led to loss of natural floodplain ecosystems that can store excess water for short periods of time and reduce and slow down water discharge. As a result, benefits to one locale can quickly translate into increased risk and vulnerability downstream when the river begins to rise. These are difficult tradeoffs which must be evaluated and negotiated among partners considering not only economic efficiencies but also social impacts and damages to the soil and water resources that are the basis of land value and use. Drained, fertile soils protected by levees support root and plant growth necessary for high levels of agricultural productivity. However, levee breaching can quickly erode and degrade soil resources resulting in changes in composition and structure and loss of soil functions, lower the soil productivity and the land's agricultural productive capacity and in some cases making it unsuitable for that use. The agricultural productivity of the land in Dogtooth Bend southwest of the proposed causeway has declined to almost zero. In contrast, including the basin floodways of un-leveed wetlands to flood during high water will much less likely result in severe soil degradation.

Recommendations
We propose the following modified options be considered [8]: 1) Expand the Dogtooth Bend peninsula floodwater storage area in the greater Ohio-Mississippi river confluence area. There is an urgency to strategically identify the area that should not be leveed so as to protect those areas that are leveed from future failure. This is critical to the economic, social, and environmental well-being of communities in Missouri, Illinois and Kentucky. Replace the current degraded Miller City to Olive Branch road with a raised causeway and the road east from Miller City to Route 3. All the former agricultural land south and west of the combined levee and raised causeway (Figure 19) would become a floodwater storage area with a land use changed to wetlands and as a wildlife habitat and or lowland forestry.
2) Coupled with increasing un-leveed floodplain storage area is the need to increase research and policy incentives for private and public landowners of these low-lying lands to profitability invest in diverse crops, wetlands and income alternatives that are resilient (able to absorb the shock) to seasonal and intra-seasonal flooding. Targeted research and conservation planning are needed to develop viable agricultural and non-agricultural uses and public payments to private land owners may be needed for ecosystem services that benefit the larger society.
3) Strengthen regional relationships on both sides of the Ohio and Mississippi Rivers at the greater confluence region to increase understanding of the impacts of different flood control and river training structures on the river and the interior landscape. Increasing the up-and down-stream citizen knowledge and understanding of these impacts will not resolve all issues but can improve recognition of the necessity of making these very difficult trade-offs so the entire region does not lose its viability. Without stronger relationships and collaborative Open Journal of Soil Science partnerships, Missouri, Illinois and Kentucky residents will compete for higher and more expensive levees rather than find cooperative solutions. 4) If the Len Small-Fayville and/or Commerce farmer levees are allowed to fail and not repaired, these bottomlands could be converted to uses that benefit from and are able to absorb seasonal and intra-seasonal temporary flood conditions, providing increased storage in the greater width for the Mississippi River between the mainline levees in Illinois and Missouri. This option could include Open Journal of Soil Science state and federal buy out, investments in research to make non-leveed floodplains profitable, landowner incentives to change uses, or some combination. To those heavily invested in leveed agricultural uses, this proposal will be difficult to accept and will require creative solutions and investments by regional partners with high levels of engagement of land owners, home owners and farmers exploring a variety of scenarios. 5) In the event the 2016 Len Small levee breach is not repaired, the agricultural land and roads on Dogtooth Bend peninsula will continue to degrade with each subsequent flooding event. If the levee breach is not repaired then we recommend the road from Route 3 to Miller City and the road from Miller City to Olive Branch be raised to become a causeway (Figure 19). This highway project could probably be funded from local and state highway funds and in partnership with the Mississippi River Commission and the USACE since the causeway will function as a levee and protect the remaining land on Dogtooth Bend peninsula from future Mississippi River flooding. The land south and west of the proposed causeway and east and north of the Mississippi River would become a permanent flood water storage area. It is also recommended that USACE create a floodwater bypass started near Mississippi River mile markers 35 and 33, across Dogtooth Bend peninsula to mile markers 17 to 13. The existing Len Small levee from the bedrock underlain upland south of Thebes gap ( Figure 2) to approximately mile marker 36 would be strengthen (perhaps a cement wall) and extended and re-aligned to the south and east of the causeway (Figure 19). The Mississippi River navigation channel would remain in the current location but USACE would need to install river training structures near the mouth of the floodwater bypass to maintain the existing navigation channel.