Story Map and ‘Path to the River’ Tool

Story Maps are interactive tools that leverage the power of geographic information systems (GIS) to tell a story. The MWMO worked with Barr Engineering and the University of Minnesota’s U-Spatial Group to create a story map that explains how and where stormwater runoff flows in our watershed, its impact on water quality in the Mississippi River, and how the MWMO monitors and treats polluted runoff. You can find our Story Map and our special Path to the River tool below.

About the ‘Path to the River’ Tool

The MWMO Path to the River application was designed to engage and educate residents of the MWMO watershed. It provides a simplified representation of how stormwater flows and is treated within our watershed boundaries. The MWMO developed this application, in partnership with Barr Engineering Co. and the University of Minnesota U-Spatial Group, with the goal of showing users that stormwater originating on the landscape within the MWMO flows to the Mississippi River, that it generally gets there quickly, and that it most often is not treated (i.e., does not flow through a stormwater best management practice (BMP) before it arrives).

The flow paths, residence times and treatment data in the Path to the River application are based on MWMO’s stormwater models and the most recent topographic data available at the time of application development (Spring 2019). Pollution potential is based on general categories of land use, which oversimplifies how pollutants are generated in our urban landscape but was deemed appropriate for the purposes of this application.

The MWMO’s stormwater models represent our best understanding of the nature of stormwater in our watershed. In some cases, professional judgement was used to manipulate flow paths or treatment areas for the purposes of simplifying model outputs for the purposes of this project. The information contained within this application is not perfect in all cases. The application contains a select number of stormwater BMPs within the MWMO; this does not represent all BMPs within our jurisdiction.

Additional Notes on Application Development

Flow Paths and Travel Times

• Flow paths were developed for a 1-inch storm event, using the MWMO’s most recent stormwater models, as the time of application development (Spring 2019). Due to the complexity of stormwater infrastructure within the MWMO, some flow paths may take a different route under larger storm events.
• A small number of flow paths (particularly in the downtown Minneapolis area and in major transportation corridors, where pipes flow over other pipes or flow particularly close to one another) have been simplified for purposes of making this application.
• In the case of areas where runoff is captured and managed under a 1-inch storm event (i.e., the area is land-locked and water does not actually make it to the river), flow paths were developed by linking the location of water management to the nearest stormwater pipe, acknowledging that runoff from that area would reach the river under larger events.
• Travel times through stormwater pipes and residence times in stormwater BMPs were also computed using a 1-inch storm event in MWMO’s stormwater models. Travel and residence times were computed using a simplified method that averages velocities and water level elevations during the middle six hours of the rainfall event, avoiding zero values and excessively low flows.

Indication of Treatment

• Indication of water quality treatment within the Path to the River application includes only select stormwater BMPs. Generally speaking, the application was developed to include large surface BMPs (both publically and privately-owned) and large, sub-surface, publically-owned BMPs. The majority of sub-surface, privately owned BMPs and small surface or sub-surface BMPs (whether public or private) were not included.

Pollution Potential

• For the purposes of this application, we define pollution potential as the amount (high, medium, or low) of pollution that can be expected to originate from a given land-use type relative to other land uses within our watershed.
• Pollution potential was assigned based on land use categories within the Metropolitan Council’s 2016 Generalized Land Use Inventory. This dataset was updated to modify land use categories within select areas of known redevelopment within the MWMO. Updates were based on the most recently available aerial photography in those areas.

Pollution potential within the Path to the River application is assigned as follows:

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