US Army Corps of Engineers
Rock Island District Website

District Projects

Iowa Reservoir Regulation Plan Studies

Published March 10, 2020

Location
Saylorville Lake, Lake Red Rock, and Coralville Lake and their associated watersheds

Description
The Corps reservoirs located in Iowa were developed for multipurpose use, however the primary purpose is flood risk management. These reservoirs have reduced peak floods in Iowa and have greatly minimized flooding in communities located below the reservoirs. Environmental and land use changes have been observed since the projects went into operation. The U.S. Army Corps of Engineers, Rock Island District (The District) is looking to developed alternatives to the current Regulation Plans to manage flood risks along the Des Moines River and Iowa/Cedar River basins. The final Reservoir revision will produce revised Regulation Plans, Environmental Assessment and Real Estate Plans. The alternatives to be examined include but are not limited to: increasing or extending maximum spring (pre-planting) releases, relaxing of Mississippi River or other constraints, seasonal variations in pool levels to maximize flood storage and increasing the dam’s storage corridors. 
It is the District's priority to develop feasible alternatives to mitigate the risk of flooding along the Des Moines and Iowa/Cedar River basins. 

Background
In July 2010, a reservoir study incorporating Saylorville, Red Rock and Coralville reservoirs was proposed to analyze alternatives to current Regulation Plans for water control and possible physical modifications to the projects. Over the last several years, the District has experienced significant flooding along the Des Moines and Iowa/Cedar rivers which resulted in levee overtopping, erosion, pump station damage and millions of dollars in personal property damage.

The results of the Des Moines River Regulated Flow Frequency Study indicated that flooding on the Des Moines River is higher and more frequent than previously estimated. Those results are also driving a need to comprehensively study Flood Risk Management alternatives for the flood control reservoir system, the SE Des Moines levee, other existing Federal and non-Federal flood risk management projects and the Des Moines and Raccoon Rivers in Des Moines, IA. 
Status
In 2015, the District conducted an initial assessment and developed alternatives to the current Regulation Plans to manage flood risks along the Des Moines River. In 2017, the District began a comprehensive Regulation Plan update. The 2 year study was completed in January 2019.  The selected plan will be incorporated into updated water control plans by 1st Qtr. FY20
In 2016, the District conducted an initial assessment and developed alternatives to the current Regulation Plans to manage flood risks along the Iowa/Cedar River Basins.  In 2019, the District began a comprehensive Regulation Plan update.  The District identified potential alternatives for the Coralville Lake Water Control Plan Update Feasibility Study with Environmental Assessment.  The District anticipates identifying a tentatively selected plan and draft report for the Iowa/Cedar River Study in 3rd Qtr. FY 2020.  The final report is expected to be complete in 2020.

Additional Information

Congressional Interest

Senators: Charles Grassley (IA), Joni Ernst (IA)

Representatives: IA-1 (Abby Finkenauer), IA-2 (Dave Loebsack), IA-3 (Cynthia Axne), IA-4 (Steve King)
Authority
OM - Operations and Maintenance

Summarized Project Costs

Estimated Federal Cost  N/A 
Estimated Non-Federal Cost N/A 
Estimated Total Project Cost  N/A 
Allocations Prior to FY 2020  N/A 
FY 2020 Allocation N/A 
FY 2020 Total Capability  N/A 

 

Major Work Item Current Year
FY 2020: The District will continue the second year of the 2 year effort to evaluate the Coralville Lake Water Control Plan Update Feasibility Study with Environmental Assessment. This effort is funded through O&M funding. A tentatively plan and draft feasibility report is currently being developed.  Reviews and Public meeting will be held this summer with final feasibility report to be completed by the end of the FY. 

The Des Moines River Regulation Manual has been updated.