Upper and Lower Dam Mitigation, Upper Iowa River

Public Informational Session: June 18, 2024

Tuesday, June 18, 2024
5:30-7:00 pm
Room 102, Olin Hall, Luther College

A public informational session on the Upper and Lower Dam mitigation will be held on Tuesday, June 18 from 5:30-7:00 pm in Room 102 of Olin Hall at Luther College.

Project partners will present potential mitigation alternatives for the Upper and Lower Dams, as well as the results of studies conducted throughout the planning process. There will be time reserved for audience questions. Following the presentation, there will be an opportunity to view and comment on the various proposals. Parking is available in the Library Lot at Luther College. 


Project Overview

The Iowa Department of Natural Resources is exploring options for mitigation of the Upper and Lower Dams on the Upper Iowa River. Project partners will investigate the current conditions of and future possibilities for the Upper and Lower Dams. The process is being guided by a plan developed by the Iowa DNR in 2010 to respond to the state’s aging low head dam infrastructure. The plan prioritizes local interests and concerns while striving to reduce dam-related hazards and balance ecological, recreational, navigational, and economical benefits. 

Primary areas of investigation and work will be led by LT Leon Associates, a civil and environmental engineering firm, and will include:

    • hosting public meetings to gather community input, feedback, and concerns regarding potential mitigation options throughout the planning process
    • developing and performing flood modeling to understand the potential for flood frequency reduction upstream for both Upper Dam and Lower Dam using on potential mitigation designs from base flow through 100-year flood
    • developing a report related to accumulated sediment behind the dams, including how much accumulated sediment there is, where it could go in different mitigation scenarios, and side-effects and tradeoffs of different options
    • surveying mussel populations in the areas around the dams where they might be affected through mitigation scenarios
    • developing preliminary conceptual mitigation designs for both Upper and Lower dams that mitigate dam hazard and fish passage issues and consider access, restoration, fishing, and other recreational concerns
    • analyzing areas of impact based on the conceptual designs, including possible areas of impact to private and public lands and historical, archaeological, and natural resources


Preliminary Public Informational Session Held APRIL 2023

Thank you to the 75+ community members who attended the preliminary public informational session on April 20, 2023 at Baker Commons at Luther College, asking great questions and sharing important thoughts, concerns, considerations, and goals regarding the Upper and Lower Dams. Written comments submitted at the meeting were compiled and shared with all project partners to support the development of preliminary conceptual mitigation designs. 


History of Upper and Lower Dams

The Upper and Lower Dams were built on the Upper Iowa River (known at the time as the Oneota River) in the early 20th Century to help meet the rising demands for electric power in the Decorah area. The river’s fall, among the steepest in the country outside of mountain streams, helps explain the 34 mills and hydro-power sites that once existed within the Upper Iowa River basin in Winneshiek County. Power from the dams along the Upper Iowa River was transmitted to Decorah, Waukon, Lansing, Cresco, Postville, and many small villages and farms in between. 

The dam sites were also utilized recreationally by local communities. The impoundment behind Lower Dam created “Lake Oneota,” a popular location for boating, picnics, and outings in the 1910s and 1920s.

By the 1930s, there was a nationwide shift away from hydropower due to the advent of coal-fired power generation, the increasing cost of repairs, and concerns over dams blocking fish passage and disrupting river flow. The costs of upkeep for the Upper and Lower Dams outweighed their economic benefit and they were shut down in 1958. The properties were purchased by the Iowa DNR in the early 1970s and the sites were managed for recreation.

Over the years, significant damage has occurred at both sites due to flooding and the aging of the dam infrastructure. The Flood of 2008 crumbled a large portion of the top of Lower Dam, changing the course of the Upper Iowa River. In January 2020, the Iowa DNR completed an emergency removal of the three damaged dam gates remaining at Lower Dam in order to preserve a downstream river access and parking area by diverting scouring flows away from that infrastructure and releasing sediment from the upstream section in a controlled manner. One of the removed gates was installed as an interpretive exhibit by the Winneshiek County Historic Preservation Commission and other partners at Trout Run Park in Decorah. 

Today, the Upper and Lower Dam sites are popular access points to the Upper Iowa River for paddling, fishing, and swimming, though they continue to present challenges to river safety, flooding, and ecology. 


Project Partners

    • Iowa Department of Natural Resources, Land and Waters and Fisheries Bureaus
    • LT Leon Associates
    • U.S. Fish and Wildlife Service
    • Northeast Iowa RC&D


For more information, please contact Paul Berland of Northeast Iowa RC&D at (563) 864-7112.