National Levee Database

Lake Waconda - Missouri River RB (NF)

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Data

Location City, County, and State of the levee system. Determined by the levee alignment location not the leveed area.

Cass County, Nebraska

System ID Unique identifier code for the levee system using 10 or 12 numbers in length.

4705000121

Operation and Maintenance Organization Entity responsible for day-to-day management of the levee.

Cass County SID#1, Lake Waconda

Emergency Management Agency Entity who supports immediate and local response to flood and other emergencies.

No Data

Floodplain Management Entities responsible for regulating activities that occur in areas prone to flooding.

FEMA Region 7

Oversight Organization Entity responsible for oversight of the levee and ensuring it is maintained.

No Data

Last Assesment Date Last Risk Assessment or Formal Inspection.

5/10/2016

Data Last Updated Date any of this information for the system has been updated.

4/27/2023

Levee Length Combine length of all the levee system features including the embankments, floodwalls, closures where they exist for this system.

2.529 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.

8 Feet

Year Levee Constructed Year levee system was fully completed as a flood reduction project.

No Data

Summary General text description of the levee system with a summary of why the levee is there, and the benefits it provides.

The Lake Waconda - Missouri River RB (NF) Segment is a single segment levee system located on the right bank of the Missouri River in Cass County, Nebraska. The Non-Federal levee segment is approximately 2.46 miles long, has a crown width of 10 feet, 2.5 to 3 Horizontal : 1 Vertical (2.5 to 3H:1V) side slopes and an average height of 12 feet. The north and south ends of the levee tie into high ground. The Cass County Sanitary Improvement District No. 1 is the Non-Federal Levee Sponsor for this levee segment. There is one drainage structure consisting of a steel pipe with a gate valve and riser located on the riverside of the levee near Levee Station 3+00. This drainage structure does not collect interior drainage and discharge it. All interior drainage flows into Lake Waconda. The drainage structure is used to pump water when necessary from the lake to the Missouri River. Construction of the levee occurred between 1984 and 1985 by a private developer for the sole purpose of providing a lakeside residential development. The levee was raised by Cass County Sanitary Improvement District No. 1 in 2010 for FEMA Certification providing a levee height equal to a 100-yr flood event plus 3 feet of freeboard. Maximum levee raise was 1.8 feet, with an average less than 1-foot. Several seepage berms were added to the project in 2011 due to seepage issues noted during the 2011 Missouri River Flood.

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.

PLEASE NOTE: The following Risk Characterization is a description of risk associated with this levee system. It is currently undergoing review and may be updated in the future. The LSOG considers the risk associated with the Lake Waconda - Missouri River RB (NF) (LST ID#2739) to be Moderate for Prior to Overtopping and Low for Overtopping. The levee has been loaded to approximately 50% of the levee height resulting in numerous sand boils that required flood fighting. The system is not expected to perform well under significant loading and it is highly likely that embankment seepage will lead to failure prior to overtopping. The foundation soils in this area consist of intermixed layers of sand, silty sand, silt and lean clay and there have been identified seepage issues during recent flood events. There is high level of community awareness and a slow rate of rise of the Missouri River. The ability to forecast the overtopping event would allow the community time to evacuate prior to overtopping reducing the likelihood of life loss. However, there is an uncertainty related to the evacuation effectiveness due to the lack of an Emergency Action Plan that includes evacuation routes or flood warning notification system.

Flooding Hazard

Historic Loading by Percentage of Height