Completed: June 2024.
Funding: Woolpert Inc. in support of the NOAA Great Lakes Restoration Initiative.
Partner: Wisconsin Wetlands Association.
Committee Overlap: Coastal Issues, Natural & Beneficial Functions.
The Marengo River Watershed in northern Wisconsin is an impaired rural watershed experiencing unnatural gullying cycles caused by land use and climate change. Climate change impacts in the Great Lakes are expected to produce more intense precipitation events. In the severe storms in 2016 and 2018, the Marengo suffered the effects of uncontrolled stormwater runoff, including widespread road failures and culvert blockages. These challenging conditions are expected to persist and worsen, increasing runoff management problems and fluvial erosion hazards (FEHs) that are already severe. FEHs strip the landscape of its natural capacity to store and slow the flow of water, contributing to downstream infrastructure failures.
This research was undertaken to help flood prone communities combine the restoration of wetland, stream, and floodplain hydrology (aka hydrologic restoration) with structural mitigation practices to reduce downstream flood risks and damages. This integrated approach is referred to as natural flood management (NFM) and offers cost-effective strategies for reducing the volume and velocity of runoff to streams, preventing future damage, protecting public safety, and preserving the health of a watershed.
The overall goals of this research were: 1) develop new methods to help characterize where the loss of wetland and floodplain storage and connectivity has occurred, and evaluate how improved restoration of storage and connectivity affects streamflow and provides opportunities to reduce downstream flood risks using nature-based solutions (NBS); and 2) develop a transferrable and replicable process and strategy that can benefit other impaired watersheds around the Great Lakes region and possibly beyond.
This project developed and used a range of interdisciplinary methods to create a holistic hydrologic conditions assessment and screening framework that links storage and connectivity functions to the built infrastructure, particularly vulnerable roads and culverts. The framework is based on catchment-level “opportunity” and “vulnerability” characteristics developed for each of the 240 sub-basins or catchments within the watershed. The primary methods used to generate these characteristics included hydrologic and hydraulic (H&H) models, a hydrologic conditions assessment, a vulnerability assessment, and identification of priority catchments through community engagement.
The project generated the data, tools, and technical capacity to help rural and tribal communities evaluate and visualize opportunities for mitigating flood and erosion hazards throughout the watershed. When possible, national, state or local data that is generally available was utilized and integrated with newly developed project data such as the Base Level Engineering (BLE) datasets that are becoming more widely available. The catchment scale approach undertaken by this project can be used as a guide for other rural watersheds.
Learn about the entire project, including findings, recommendations and detailed descriptions of each project phase: Final Report: Assessing Flood Vulnerabilities and Nature-Based Solutions, Marengo River Watershed, WI
All project-related information is publicly available through the Natural Flood Management Hub site hosted by the Flood Science Center. The Hub site includes an interactive map viewer and more.
See also, NOAA's project description Marengo River Watershed: Understanding Wetland Ecosystem Benefits and Variability.