Upper Mississippi River Basin
The current Upper Mississippi River and Illinois River flow frequency study, completed in 2004, was created using a period of record ending in 1998. Since then frequent and record setting major floods have occurred. The flood of 2019 was not only historic with regards to flood heights, but also in its duration. The Mississippi River was above flood stage at Cape Girardeau for 145 days. In addition, many communities between Dubuque, Iowa and St. Louis, Missouri have experienced the majority of their top 10 flood crests in the past 20 years. Significant flooding on the UMR occurred in 2001, 2008, 2011, 2013, 2014, 2018, and 2019. The Illinois River has experienced the same unprecedented flooding. At Peoria, IL (on the IWW), 5 of the 10 highest flood crests have occurred since 1998, including the record crest in 2013.
This effort will update the flood flow frequency profiles on the Upper Mississippi River from Birds Point (Mile 0.0) to through Anoka, MN (864.8), and the Illinois River from Grafton (Mile 0.0) to Dresden Island Lock and Dam (Mile 271.5). Previous methodologies will be reviewed and modified as needed to confirm they meet the current state of the practice of flood frequency calculation. The study will utilize input data gathered during the previous flow frequency effort, augmented with new observed data to complete a 122 year period of record (1898 to 2020). Completion of the proposed study, utilizing the updated period of record and new federal guidelines for determining flood flow frequencies, Bulletin 17C, will improve confidence and reliability of flow frequencies on the UMR and IWW to support flood risk management planning and communication and the USACE Dam and Levee Safety Programs. This will provide an opportunity to incorporate available climate change into the analysis of a large river system using the latest USACE Guidance. Updated frequency profiles and associated documentation will be published at the completion of this effort.
The benefits of an updated flow frequency study on the Upper Mississippi and Illinois Rivers will be realized immediately and ensuring water resource decisions are made using current and accurate data will provide a considerable value to the nation. The Corps continually engages with watershed stakeholders through its various programs and authorities. These stakeholders routinely ask what the effects these recent common and historic floods are on the previously calculated frequencies and have requested this data be included when making water resource decisions.
From FY 18 to present, the Corps provided technical assistance to the Upper Mississippi River Basin Association (UMRBA) on a Planning Assistance to States effort to identify Upper Mississippi River actions that have consensus and could have an immediate benefit. One of the high leverage actions identified in the UMRBA’s draft report included updating the flow frequencies. This information was viewed as fundamental to future planning and decision making. In addition, the Corps has been advancing the development of HEC-RAS hydraulic models on the Upper Mississippi and Illinois Rivers. The updated models on the Upper Mississippi River are complete and can be immediately utilized for updating the flow frequencies, which will save time and money.
This project is a potential new start project.
If funded, major tasks in this effort include:
- HEC-HMS models will be used to compute local inflow for the period of record.
- Existing HEC-RAS models will be used to route the period of record flows and compute profiles for frequency analysis.
- Existing CWMS models from regulated basins within the study area will be utilized as needed to route inflow and provide regulated vs unregulated flow information.
- Development of an interagency team which will include USACE (MVS, MVP, and MVR), FEMA, USGS, NWS, NRCS, and state agencies from Missouri, Illinois, and Iowa.
- Internal review and coordination will be conducted within the HH&C CoPs from MVD and HQ, and with HEC, the USACE Climate Change team, and the USACE hydrology committee, as required. Additional outside expert assistance may also be required
In FY21, $320,000 in funding was provided through an on-going Lower Mississippi River Basin Flow Frequency Study to develop an advanced scope of work for the UMR Flow Frequency Study. The UMR is a major contributor to the flows on the Lower Mississippi River, and any data developed from the UMR flow frequency study must be consistent and compatible with this on-going study.
FY21 – Special Studies
FY22 or beyond - General Investigations Floodplain Management Services (FPMS) or Remaining Items
Summarized Project Costs
Estimated Federal Cost
Estimated Non-Federal Cost
Estimated Total Project Cost
Allocations Prior to FY 2022
FY 2021 Allocation
FY 2022 Allocation
FY 2022 President's Budget
FY 2022 Total Capability
Major Work Item Prior Fiscal Year
FY 2021: The project moved forward with completing and coordinating an advanced scope of work and assessment approach with the Hydrologic Engineering Center and other federal partners; developing a detailed cost estimate and schedule, developing a comprehensive review plan, advancing a qualitative climate assessment, and conducting data gap analysis.
Major Work Item Current Year
FY 2022: If funded, work will proceed with continuing to advance Phase I of the study. Major activities will include completion of data collection, completion of climate assessment, and development of the Hydrologic Management Plan for public coordination and review.