Fluvial Erosion Hazard Rapid Geomorphic Assessment Data from the Marengo Watershed, Ashland County, Wisconsin

An extreme flood in 2016 caused widespread culvert blockages and road failures across northern Wisconsin, including extensive damage along steep tributaries and ravines in the Marengo River watershed. Along with the flooding, there were fluvial erosion hazards (FEH) associated with a large amount of erosion in headwater areas. Of special concern were FEHs associated with gullying, loss of wetland storage, and valley-side mass wasting. In 2020, a pilot study was begun to map and classify ephemeral and perennial streams and wetlands in terms of their susceptibility to fluvial erosion hazards. This study combines rapid geomorphic field assessments of river corridor erosion and coupled sediment and debris delivery with mapping geomorphic vulnerability zones in a Geographic Information System (GIS). The FEH assessment results will ultimately be used to identify and prioritize natural flood management projects related to stream and wetland restoration.