Flood Mitigation Project

Over the next two years, a major construction project will take place at Herbert Hoover National Historic Site. On this page, we will explain why the project is needed, what will happen, when it will occur, and provide updates as things proceed. Planning and research documents regarding Hoover Creek, including the Environmental Assessment and Finding of No Significant Impact for this project, may be found by clicking here. If you have any questions, please feel free to email or call Ranger Garrett Cloer at (319)643-7860.

Collage of four images showing flooding in the park threatening historic resources and park infrastructure such as the birthplace cottage, visitor center, roads, and parking lots.


Most of the time, Hoover Creek is peaceful and innocent. However, it's character quickly changes during heavy precipitation events which can cause the creek to rapidly exceed its banks. This happened three times in 2018 alone. Climate data shows that these heavy precipitation events increased 37% from 1958 to 2012, a trend that is expected to continue.

These floods:
• ...can result in closures of park areas.
• ...threaten the site’s cultural landscape, archeological resources, and historic structures.
• ...require extensive cleanup after the waters recede.

Other issues have also argued in favor of the project. Changes in the channel beneath the Downey Street Bridge and damage caused by flood events have altered the appearance of the area and created restrictions to water flow. The historic limestone wall by the bridge has been damaged by floodwaters over the years as well. In addition, Hoover Creek has lowered the creek bed over the years through erosion, changing the very shape of the channel and its banks. This has made maintenance of the creek banks and surrounding areas increasingly more difficult, changed the historic appearance of the creek, diminished visitor access and enjoyment, and affected the health of the stream.
Aerial picture of the park. The City of West Branch is to the top. Hoover Creek runs through the middle and the prairie covers the bottom third. Construction zones around the creek are marked.
Aerial view showing the Hoover Creek Flood Mitigation Project plan and areas of construction.

What is happening and when?

The project contains four key elements of construction. These are:

  • A 10.1-acre detention basin will be built to provide an outlet for excess water during and immediately following heavy rain events. This element is designed to act as a safety valve relieving the pressure on the creek system to drain the high amounts of water, holding it until it can safely flow downstream.

  • The stream channel will be widened and the steep angle of the banks reduced. This will allow the banks to be maintained in their historic appearance and allow more water to be transported through the system. It is also anticipated that this portion of the project will increase the health of the stream.

  • A new Downey Street Bridge will be constructed and the historic limestone wall repaired. This will help restore the appearance of the bridge and wall to its original design and improve the flow of water under the bridge, lessening obstructions which can result in flooding.

  • Dirt removed from construction areas will be used to build sound mitigating berms along I-80 and Parkside Drive. These will reduce sound pollution in the reconstructed tall grass prairie, increasing visitor enjoyment and improving wildlife habitat.

Complete construction is expected to take approximately two years. The first, preparatory steps will begin in March 2020. This will include tree removal along the banks of Hoover Creek, followed by relocation of utilities and infrastructure and further archeology in affected areas. The major construction listed above will begin in September 2020 and is expected to be largely complete in April 2021. Replacement tree planting and seeding of lawn areas will follow through early 2022. Updates will be provided below as the project progresses.

Overview of bridge deck. Smoothed greyish concrete completely covers the surface. Breen metal rebar stand about three feet tall on each side where railings will be poured. The concrete conveyer boom is visible on the opposite creek bank, partially extendi
Downey Street Bridge construction

NPS Photo

Current Status

July 2021: Construction is largely completed! Periodic work may continue on revegetation portions of the project.

Spring 2021: Work continues at the detention basin.

12/16/2020: Abutments and deck for Downey Street Bridge are poured. Construction continues on Detention Area. New photos have been added to photo gallery below.

11/12/2020: Footings for the Downey Street Bridge are complete and forms are being built for pouring the bridge structure itself. Construction has started in the west prairie area on the detention basin.

11/05/2020: Construction work on Hoover Creek itself is nearly complete. Work continues on the foundations for the new Downey Street bridge and excavation for the retention basin is expected to start soon.

10/26/2020: Downey Street bridge removed.

09/15/2020: Safety fences around construction areas on Hoover Creek are being installed. Haul roads and berm sites are being prepared. Prairie trails and Friends Meetinghouse are closed until further notice.

03/20/2020: Tree cutting and brush removal along Hoover Creek completed. Images are available here.

Last updated: July 5, 2021

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P.O. Box 607
West Branch, IA 52358


(319) 643-2541

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