Rock Island District / Missions / Flood Risk Management / Upper Mississippi Flow Frequency Study

Upper Mississippi River System Flow Frequency Study Update

ST. PAUL DISTRICT - ROCK ISLAND DISTRICT - ST. LOUIS DISTRICT

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

 

Frequently Asked Questions

Collapse All Expand All
Expand List item 37339Collapse List item 37339  Why is this project needed?

There are multiple reasons to update the 2004 Flow Frequency findings: the systematic hydrologic record is longer, several large floods have occurred in the study area since 1998, guidance for flow-frequency estimates has been updated to Bulletin 17C, hydraulic modeling software technology has advanced. Flow frequencies should be updated to provide water resource managers the most current and accurate data for decision making in the Upper Mississippi River watershed.

Expand List item 37340Collapse List item 37340  How long will the project take?

The project will take 4 years to complete, based on consistent and adequate funding. Insufficient funding will likely lead to schedule delays.

Expand List item 37341Collapse List item 37341  How much will the project cost?

The total project cost is $4,200,000. Of that total cost, the study received approximately $1,760,000 from Fiscal Years 2021 to 2024.

Expand List item 37342Collapse List item 37342  How is the project being funded?

In Fiscal Year 2024, Congress appropriated $1,000,000 for the project.

Expand List item 37343Collapse List item 37343  Who is involved in the update?

Due to the extensive geographic scope, all 3 USACE Districts (St. Paul, Rock Island, St. Louis) in the Upper Mississippi River are contributing to the study.

Expand List item 37344Collapse List item 37344  For what years will flow observation data be included in the study update?

This study builds upon the 2004 UMR Flow Frequency Study's dataset with new observations, extending the period of record from 1898 to 2024, adding over 25 years of new hydrologic data. The study’s flow dataset will continue to be inventoried analysis and modeling begins.

Expand List item 37345Collapse List item 37345  Where will the information be made available upon completion?

Once flow profiles and stages have been updated, reviewed, and approved, then the information will be provided via USACE webpages or via email.

Hydrologic Engineering Management Plan

Contact Us

Questions or comments regarding the Upper Mississippi River Flow Frequency Study can be sent to publicinvolvement@usace.army.mil. 

2004 Flow Frequency Study Final Report