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Prairie du Rocher / Edgar Lake System Location
City, County, and State of the levee system. Determined by the levee alignment location not the leveed area.
Randolph County, Illinois
System ID
Unique identifier code for the levee system using 10 or 12 numbers in length.
5605360001
Operation and Maintenance Organization
Entity responsible for day-to-day management of the levee.
Prairie Du Rocher/ Modoc Levee & Drainage DistrictEdgar Lake Drainage and Levee District
Floodplain Management
Entities responsible for regulating activities that occur in areas prone to flooding.
FEMA Region 5
Oversight Organization
Entity responsible for oversight of the levee and ensuring it is maintained.
USACE - St Louis District
Last Assesment Date Last Risk Assessment or Formal Inspection.
6/4/2019
Data Last Updated Date any of this information for the system has been updated.
4/24/2025
Levee Length
Combine length of all the levee system features including the embankments, floodwalls, closures where they exist for this system.
16.504 Miles Average Levee Height
The average height of the levee system. The levee profile viewer on the mapping window will show the actual levee height values for the length of the levee if available.
25 Feet Year Levee Constructed Year levee system was fully completed as a flood reduction project.
1955 Summary
General text description of the levee system with a summary of why the levee is there, and the benefits it provides.
The Prairie Du Rocher & Modoc and Edgar Lakes levee system reduces the risk of flooding from the Mississippi River to the Randolph County, IL agricultural lands and communities of Prairie du Rocher and Modoc. The system is federally authorized and constructed and locally operated and maintained by the nonfederal Sponsors, Prairie du Rocher and Modoc Levee & Drainage District and Edgar Lake Drainage and Levee District. The federal levee system was originally completed in 1955, however modifications were made between 1999 and 2002 that included raising sections of the levee. The levee system consists of 16.5 miles of earthen embankment along the Prairie du Rocher Creek, Mississippi River, and Kaskaskia River. Within the 16,570-acre leveed area are Illinois Route 155, and multiple residential, commercial, and industrial properties including several oil gas pipelines and a farm service center. The system provides benefits to approximately 586 residents and employees and approximately $29.6 million in property value. During the 2016 flood event, the system prevented an estimated $8.3 million in flood damages.
Performance & Condition
General text description of the historical and anticipated performance of the levee, the people and property benefitting from the levee and who may be at risk of flooding, and actions to address areas of concern.
The Prairie du Rocher & Modoc and Edgar Lakes levee system has prevented Randolph County communities from flooding during numerous major flood events. However, during recent flood events, uncontrolled seepage has been observed throughout the system and remains a primary concern. While some water seeping through and under the levee is normal in this region, seepage in several locations has been severe enough to move soil particles from beneath the levee and deposit the material on the landside in the form of sand boils, which weaken the levee. The original features used to control these effects are aged and have decreased effectiveness. The extent of damage sustained within the levee system’s soil due to sand boils and seepage from previous floods is unknown. There is a possibility that in any given year floodwaters could overtop or breach the levee system. A levee failure could result in flooding of depths up to 21 feet, loss of life, and significant economic damage.
Flooding Hazard
Historic Loading by Percentage of Height
Representative loading associated with historical flood information as a percentage of the levee height or overtopping.
Representative loading associated with historical flood information as a percentage of the levee height or overtopping.
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