As part of a pipeshed and water-quality project, Barr created a citywide, GIS-based model that provides an estimate of how well stormwater best management practices (BMPs) in the city of Minneapolis are removing total phosphorus and total suspended solids from stormwater runoff. The catch-basin-to-catch-basin, cluster-level model utilizes the city’s stormwater geometric network to describe flow patterns to approximately 500 outfalls and includes more than 1,300 BMPs, 28,000 watersheds, and 70,000 junctions. The GIS data model incorporated stormwater data from Minneapolis, 10 neighboring cities, and the University of Minnesota. Additional land-use, land-cover, and LiDAR data from state and federal sources were used to develop raster surfaces needed for predicting runoff and pollutant loadings, as well as for detailed watershed delineation.
The completed model allows for the evaluation of “what if” scenarios regarding BMP placement, street sweeping frequency, and other potential changes to the city’s stormwater system. Since the model utilizes GIS network and feature classes, pollutant loading and removal can be summarized anywhere within the drainage system upstream of the outfalls. Barr also provided in-person model training and support for city staff.
The city can use this tool to identify, analyze, and prioritize water quality areas of concern and evaluate a variety of city initiatives. For example, this model will allow the city to target high-pollutant-generating areas and incorporate water quality BMPs into planned capital projects. This multiple-benefits approach enables the city to prioritize where water quality projects are implemented to maximize city resources and reduce pollution of surface waters.