Presenter Information

Megan OttenFollow

Abstract

Spanning almost 1,700 square miles over six different counties (Dodge, Filmore, Houston, Olmsted and Winona) in southeastern Minnesota, the Root River Watershed is one of the state’s largest watersheds draining into the Mississippi River. The Root River Watershed is within the Driftless area, which has a unique set of characteristics that present certain challenges when it comes to watershed mapping and management. The Driftless area, consisting of Paleozoic limestone, dolostone and St. Peter sandstone, is characterized by its karst features and highly incised, heavily forested valleys. Soil erosion and farm field runoff are two of the Minnesota Pollution Control Agency’s (MPCA) main concerns in the watershed due to the bedrock geology, steep slopes, and large areas of farmland. The Minnesota Department of Agriculture estimates that 44% (280,000 tons) of the Root River’s sediment load comes from bluff-top farm fields. The excess sediment and nitrates in the watershed’s streams have been affecting not only the ecosystems in the immediate area, but also many ecosystems downstream on the Mississippi River, leading to the Gulf of Mexico. These negative impacts can potentially be reduced by the construction of structural Best Management Practices (BMPs), like Water And Sediment Control Basins (WASCOBs), pond dams, terraces, and grassed waterways.

In 2019, the MPCA commissioned the Root River Watershed Structural BMP Mapping Project, aimed at mapping BMPs in the Root River Watershed and calculating the area of land being treated, by using both LiDAR-derived topographic data and satellite imagery. All WASCOBS and pond dams in the Root River Watershed were mapped and given a confidence level based on their shape and condition. The area treated by the BMPs was found by calculating the watersheds for each feature, which were then field checked to ensure the accuracy of the watersheds. Currently, about 19% (190,000 acres) of the Root River watershed is being treated by WASCOBs and pond dams. Pond dams are generally evenly distributed among the watershed’s farmland while WASCOB distribution is restricted to the moderately flat areas of farmland in the watershed. The areas that would benefit from more BMP construction have moderate-high risk of soil erosion, large amounts of farmland, and a low density of existing BMPs. This inventory, along with identified risk areas will be used by watershed managers as guidance for future BMP construction projects.

College

College of Science & Engineering

Department

Geosciences

Location

Winona, Minnesota

Breakout Room

24

Start Date

4-14-2021 1:00 PM

End Date

4-14-2021 1:45 PM

Presentation Type

Poster (PDF)

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Apr 14th, 1:00 PM Apr 14th, 1:45 PM

Mapping and Analysis of Structural BMP's in the Root River Watershed, MN

Winona, Minnesota

Spanning almost 1,700 square miles over six different counties (Dodge, Filmore, Houston, Olmsted and Winona) in southeastern Minnesota, the Root River Watershed is one of the state’s largest watersheds draining into the Mississippi River. The Root River Watershed is within the Driftless area, which has a unique set of characteristics that present certain challenges when it comes to watershed mapping and management. The Driftless area, consisting of Paleozoic limestone, dolostone and St. Peter sandstone, is characterized by its karst features and highly incised, heavily forested valleys. Soil erosion and farm field runoff are two of the Minnesota Pollution Control Agency’s (MPCA) main concerns in the watershed due to the bedrock geology, steep slopes, and large areas of farmland. The Minnesota Department of Agriculture estimates that 44% (280,000 tons) of the Root River’s sediment load comes from bluff-top farm fields. The excess sediment and nitrates in the watershed’s streams have been affecting not only the ecosystems in the immediate area, but also many ecosystems downstream on the Mississippi River, leading to the Gulf of Mexico. These negative impacts can potentially be reduced by the construction of structural Best Management Practices (BMPs), like Water And Sediment Control Basins (WASCOBs), pond dams, terraces, and grassed waterways.

In 2019, the MPCA commissioned the Root River Watershed Structural BMP Mapping Project, aimed at mapping BMPs in the Root River Watershed and calculating the area of land being treated, by using both LiDAR-derived topographic data and satellite imagery. All WASCOBS and pond dams in the Root River Watershed were mapped and given a confidence level based on their shape and condition. The area treated by the BMPs was found by calculating the watersheds for each feature, which were then field checked to ensure the accuracy of the watersheds. Currently, about 19% (190,000 acres) of the Root River watershed is being treated by WASCOBs and pond dams. Pond dams are generally evenly distributed among the watershed’s farmland while WASCOB distribution is restricted to the moderately flat areas of farmland in the watershed. The areas that would benefit from more BMP construction have moderate-high risk of soil erosion, large amounts of farmland, and a low density of existing BMPs. This inventory, along with identified risk areas will be used by watershed managers as guidance for future BMP construction projects.