The current flood flow frequency study for the Upper Mississippi River and Illinois River, completed in 2004, was based on data up to 1998. Since then, numerous major floods, including the historic flood of 2019, have occurred. Many communities between Dubuque, Iowa, and St. Louis, Missouri, have experienced top 10 flood crests in the past 20 years, with the Illinois River seeing similar unprecedented flooding.
To address these changes, this effort aims to update the flood flow frequency profiles for the following river segments:
- Upper Mississippi River: From Birds Point (Mile 0.0) to Anoka, MN (Mile 864.8)
- Illinois River: From Grafton (Mile 0.0) to Dresden Island Lock and Dam (Mile 271.5)
The study will utilize input data gathered during the previous flow frequency effort, augmented with new observed data from present, to create at least 25 years of new hydrologic data.
The U.S. Army Corps of Engineers regularly engages with watershed stakeholders who have expressed interest in better understanding how recent floods are affecting previously calculated frequencies. They have requested that this data to inform water resource decisions. Updating the study on the Upper Mississippi and Illinois rivers will have immediate benefits, ensuring that water resource decisions are made using current and accurate data, and providing significant value to the nation.
Status
The project was partially funded in fiscal years 2021-2023 for development of a detailed scope of work, inventorying existing data and performing Part I of an Engineering Change Bulletin 2018-14 Climate Change Assessment. With funding received in fiscal year 2024, the project team will complete formulation of a Hydrologic Engineering Management Plan, consult with internal and external experts regarding the HEMP, and initiate development of a hydraulic routing model.
If additional funding is provided, major tasks in this effort include:
- Development of a homogenous unregulated and regulated daily flow time series.
- Perform Part II of the Climate Change Assessment
- Annual peak mainstream flow frequency analysis
- Development of hydraulic profiles
- Finalize report and study products