Purpose
The Navigation and Ecosystem Sustainability Program (NESP) is a long-term program of ecosystem restoration and navigation improvements for the Upper Mississippi River System.
The Sny Magill unit of Effigy Mounds National Monument in Iowa is located within the floodplain of Pool 10 of the Upper Mississippi River between river miles 626 and 628 along Johnsons Slough.
The Sny Magill unit protects more than 100 Native American burial and ceremonial mounds, which are important to the 19 federally recognized tribal nations with which Effigy Mounds National Monument consults. The park and the tribal partners consider the mounds unique and irreplaceable sacred cultural features of national significance.
The gravel outwash terrace underlying the mound group sits at a higher elevation than surrounding islands. Altered hydrology within the pool has created conditions such that the substrate can be undercut and/or saturated during high water events, causing bank failure. Several mounds have been damaged in past events. Previous National Park Service efforts to stabilize the eroding bank have had limited success. Prolonged high water levels from 2018 to 2021 severely impacted the bank, and six mounds are now in immediate jeopardy. Accelerated erosion and sedimentation may also be impacting vegetation and mussel communities within the slough.
Description
This NESP study is a partnership with the National Park Service, U.S. Fish and Wildlife Service, Iowa Department of Natural Resources, Wisconsin Department of Natural Resources, and U.S. Army Corps of Engineers. The study will consider alternatives including riverbank stabilization and protection, floodplain restoration, closure or partial closure structures, and in-channel diversion structures.
Status
The Project Implementation Report was approved by the Mississippi Valley Division in June 2024. Design development will continue into 2025, with a construction contract award anticipated in fall 2025. Construction may commence in summer of 2026 and continue through 2027.
Authority
This work is authorized under Title VIII, General Investigations, of the Water Resources Development Act of 2007.
Funding
This project is expected to be constructed below the ordinary high water mark and therefore will be 100% federal funded. Operations and maintenance are the responsibility of the project sponsor.
Funds allocated to date ~$1.41 million
Anticipated construction cost ~$7.73 million