Storm events have eroded the existing Sauk Creek greenway channel banks. These eroded banks send sediment and nutrients downstream, fill in ponds and waterways, and contribute to harmful algae blooms. This has a negative impact on our downstream ponds, waterways, the Pheasant Branch Conservancy, and lakes Mendota and Monona. Stabilizing the banks of badly eroding channels is in alignment with the City of Madison Comprehensive Plan, Imagine Madison, to improve lake and stream water quality. And, in alignment with the Renew the Blue guide from the Yahara CLEAN compact, which specifically lists stabilizing drainage corridors as a recommended action. Additionally, in order to be compliant with State and Federal laws, we need to maintain stable stormwater channels.

As a result of the continued erosion, there are many trees adjacent to the channel that have fallen within the channel. This can reroute stormwater into new channels in the greenway, causing further erosion in a self-reinforcing cycle of erosion and subsequent tree loss.

Additionally, the City does not have access to the majority of the channel, apart from portions of the sanitary access road that are adjacent to it, to be able to remove fallen trees and larger blockages from the channel. To allow for future channel maintenance, and as part of any future construction project, a maintenance access path along the greenway is necessary.

The Sauk Creek Greenway is an important component of the Pheasant Branch Watershed. A comprehensive flood study was completed for this watershed following the August 20, 2018 flood event. Approximately ~1,230 acres of the watershed drain through this greenway! That results in ~260 cubic feet per second (CFS) of water flowing through the greenway during the 50% annual chance storm event (a type of summer storm we see most years). 1 cubic foot per second (CFS) can be hard to visualize. One way to put this into a bit of perspective is that one (1) CFS equals 450 gallons per minute (GPM), and a garden hose puts out approximately 12 GPM. So 1 CFS is equivalent to about 37 garden hoses (that is a lot of water).

The City continues to invest in green infrastructure solutions for public works, and stormwater regulations have been modified to require new developments that occurred after 2011, to infiltrate 90% of the water that previously infiltrated naturally prior to development. Additionally regulations were modified in 2020 that requires redevelopments that did not originally have infiltration requirements to now infiltrate 5% of the 10-year storm event. These efforts alone will not be sufficient to allow us to reach our flood targets throughout this watershed, due at least partially to all the development that occurred prior to any significant stormwater management requirements. As a result, we need to accommodate more stormwater in our main conveyance system, including the Sauk Creek greenway. The Sauk Creek greenway channel will be designed to be stable once upstream flood improvements are made so this channel will be stable for the next generation.

The consultant that is completing the Ecological and Channel Assessment will be analyzing the stormwater flows through the greenway from the Pheasant Branch watershed study and developing sample cross sections for the community to provide input on. One cross section will focus on tree preservation, and one cross section will focus on natural channel design. These cross sections will be shared during the Concept Refinement step (the public meeting in winter 2023-2024).


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