Spring Harbor Watershed Study
Thank you all for your questions, feedback, and comments on the Spring Harbor Watershed Study Final Draft Report, dated October, 2021. The City received 58 comments and over 100 individual questions during the comment period. We appreciate your patience as we worked on replies to your thoughtful questions. The time and effort each of you took to submit comments truly helps to make our study better. Please see the Questions from Spring Harbor Comment Period document for responses to your questions. Note that in many cases, we have provided links to additional information on the City’s website.
There are some questions that we are unable to answer without completing additional watershed computer modeling. This computer modeling will be conducted over the next six months. Once we have the results of the computer modeling, we will be hosting a 4th Public Information Meeting. The computer modeling will include 29 model scenarios. These scenarios will 1) provide information to refine the selected solutions, 2) help the City re-set a solution implementation order, and 3) complete design-level modeling for the Regent Street culvert. There is more detail on the modeling specifics below.
As a reminder, Engineering was tasked with finding out what it would take to meet the City’s flood targets. Following the historic flood events in 2018, the Common Council tasked Engineering with specifically dedicating resources to understand how to solve flooding in all the watersheds in the City. The flood targets include preventing damage to private structures during a 1% annual chance (100-year) storm event, and keeping collector and arterial streets passible to emergency response vehicles in smaller events. The watershed studies fulfill the task assigned by the Common Council.
Many of the solutions are traditional stormwater management solutions for a built environment. There are three main reasons for this:
- Traditional stormwater management is currently the lowest cost treatment technology available
- Spring Harbor is a fully developed watershed with an urban stormwater management system
- Engineering conducted a separate effort to understand how much Green Infrastructure was needed to meet the flood targets
The computer models developed for the watershed studies help the City understand the causes of flooding and which mitigation techniques will help the City meet its flood reduction targets. Because many of the watersheds are hydraulically complex, the computer models also help Engineering understand the complexities of each watershed and how each component within each watershed work together.
The studies are used to help the public and policy makers understand the magnitude of the issues in each specific study area and to educate residents on how the drainage system functions. This allows residents, property owners, and policy makers to make informed decisions on how and when to implement projects. It also helps them understand what the projects may entail, if and what limitations each project could have, and make decisions if we should even implement a proposed project at all.
The solutions documented in the watershed study reports are not meant to be full design-level efforts; they are conceptual solutions that help Engineering understand the magnitude of solution needed in a given area to meet the flood reduction targets. As projects are looked at further, and if they move to the point they are budgeted, then projects will then go into a more detailed design phase. This project phase collects detailed data needed for design and looks at refined design, permitting, environmental issues, and potential co-benefits associated with the particular project. Those design level projects will have separate public engagement components that can help address detailed questions and concerns.
The City is systematically studying all 22 watershed in the City. Currently there are well over $200M worth of flood mitigation projects that are currently identified in less than 1/3 of the city. Correcting systemic and historic flooding issues will take decades. Funding for projects will be difficult and if there is limited support those funds would be prioritized to other projects.
The goals of the additional computer modeling that will be conducted for the Spring Harbor Watershed Study are outlined below:
Provide information to refine the selected solutions: the City will be looking at feasible solution ideas from the public comment period to understand if the proposed ideas can meet our flood goals. The City will also look to understand if the proposed ideas modify the overall recommended suite of solutions. This modeling takes time and effort. This is because when one solutions is changed, it may impact upstream or downstream solutions. A few examples of things that will be looked are:
- Re-routing the sanitary sewer that crosses the Forsythia cunette (concrete bottom channel) so that we can deepen and widen the channel. This information will be compared to the flood reduction from the flood wall conceptual solution.
- Add a bypass pipe along South Kenosha Drive to bring water from Burnette Drive downstream to Regent Street. This will be reviewed to understand if this can reduce the need for re-grading the Kenosha Greenway.
- Iterate the size of the replacement of the culverts under Regent Street at Kenosha Drive: the existing culverts under Kenosha Drive are in poor condition and are scheduled for replacement. The City plans to install the proper sized culverts to meet future flood mitigation goals during the replacement but would put restrictor plates in place so it does not flood out downstream properties until the necessary infrastructure is in place first. To complete the additional computer modeling for the culvert installation, the model will be updated to reflect current watershed conditions. Once that is complete, the Regent Street culvert will be sized for both-short and long-term capacity needs.
- The City anticipates replacing and upsizing the culvert under Regent Street in 2023. This replacement culvert will likely be oversized for current downstream conditions. A restrictor plate will be installed with the oversized culvert. The restrictor plate will reduce the flows coming through the culvert until the downstream capacity improvements are made.
- A separate public meeting will be held to discuss the Regent Street culvert design and get resident feedback. This will be in addition to the 4th Spring Harbor Watershed Study Public Information Meeting.
- Create a near-term plan for Spring Harbor flood mitigation projects: Once we have the revised recommended suite of solutions and a plan for the Regent Street culvert replacement, we will create an implementation order that considers the feedback received, as well as the most impactful ways to reduce flooding watershed-wide.
- During this process, the City will review the individual impact of the most controversial solutions to better understand the tradeoffs that occur from implementing them versus not implementing them.
As mentioned above, we anticipate hosting a 4th Public Information Meeting in early 2023. During this meeting, we will present our modeling findings, and provide a space for more questions from residents. Please subscribe on the right hand side of this webpage to receive updates on the project.
The City of Madison will complete a watershed study in the Spring Harbor watershed (as shown below). The watershed study will identify causes of existing flooding and then look at potential solutions to try to reduce flooding. The study will use computer models to assist with the evaluations. A local engineering consultant, Advanced Engineering and Environmental, will complete the study. For more information please see the Flash Flooding Story Map. For a brief summary about how the flood model was built, and to see the flood model results, visit the Spring Harbor Flood Model Results Story Map.
*Note: Please view the story maps using Firefox or Google Chrome browsers. Story maps are not viewable with Internet Explorer.
During the June 30, 2021 Spring Harbor Watershed Study Public Information Meeting attendees asked several questions about the effects of the proposed solutions on erosion in City greenways and/or scouring at the harbor/outfall. City staff compiled a Frequently Asked Questions document to answer these questions: Spring Harbor Outfall Repair and Dredge FAQ. PDF For more information about the related projects, you can view the Spring Harbor Outfall Repair project and the Spring Harbor Dredge project webpages.
Help the City understand what you want to prioritize flooding projects. Please take our survey and learn more about how we're working to prioritize stormwater improvement projects in our community.
The Spring Harbor watershed drains toward Spring Harbor on Lake Mendota.
The watershed studies take 18-24 months to complete. The first studies will take longer as the City works through the best processes and approaches for this new flood study initiative.
There are a number of points of contact during this project where the public is encouraged to give feedback as part of public information meetings and public hearings. Dates and times are indicated below:
Public Information Meetings
- June 30, 2021 Public Information Meeting Recording
- June 30, 2021 Public Information Meeting PowerPoint Presentation
- April 25, 2019 Public Information Meeting PowerPoint Presentation
- Feb. 24, 2020 Public Information Meeting PowerPoint Presentation
- Frequently Asked Questions about the Watershed Studies
Focus Group Meetings
In the summer and fall of 2019, the City of Madison Engineering Division hosted a variety of focus groups for known flooding areas within the watershed.
The following focus group meetings occurred in this watershed:
- Mineral Point Park to Owen Park, 4-5 p.m., Aug. 28, 2019 Corner of Quarterdeck Dr and the bike path, about 150 feet north of the intersection of Landfall Dr and Quarterdeck Dr on the east side of the street
- Owen Park Concrete Channel, 6-7 p.m., Aug. 29, 2019 Corner of Forsythia Pl. and Bordner Drive
- Regent Street, Burnett Drive and Calumet Circle, 4-5 p.m., Aug. 29, 2019 Corner of Burnett Drive and S. Kenosha Drive
- Marbella Condo Association, 2-3 p.m., Aug. 30, 2019 Outside Marbella Tennis Court gates near corner of South Yellowstone Drive and Mineral Point Road
- Oakwood Village Association, 2-3 p.m., Sept. 18, 2019 inside meeting room of Oakwood Village Center for Arts and Education
- Bordner Park, 6-7 p.m., Sept. 19, 2019 Bordner Park Playground, 5600 Elder Place in center of park
- West Towne Pond, 3-4 p.m., Sept. 16, 2019 Schwoegler Park Towne Lanes Banquet Hall, 444 Grand Canyon Drive
- Spring Harbor Neighborhood Association, 5-6 p.m., Oct. 3, 2019 Spring Harbor Park Playground (corner of Spring Harbor Drive and Lake Mendota Drive)
Additionally, people within focus groups were involved in breakout sessions during the second public meeting on February 24, 2020. Residents were able to sit with engineering staff to provide feedback on where the drainage model predicted flooding during certain rain events.
Existing Conditions Flood Mapping
The watershed model evaluated numerous design storm events. The City created an online viewer for the 1% chance (100-yr) storm event. It can be found here.
Proposed Flood Reduction Solutions
The watershed study resulted in many proposed flood reduction solutions. These solutions are concepts and show what it would take to meet the City's flood reduction targets. Only solutions included in the Capital Improvement Program budget are in process of design or construction; public outreach efforts are conducted for those projects separately from this study. The map below shows the locations and extents of the proposed solutions. Concepts for individual solutions can be found in the Draft Final Report posted above.
The City of Madison has 22 watersheds. Watersheds are an area of land that drain to the same location (the outlet).
There is a stormwater drainage system in all watersheds. This system is what conveys the stormwater to the outlet of the watershed. The current statistics on the City of Madison's stormwater drainage system can be found on the Stormwater webpage.
The City's system dates back to the 1880s. Very few, if any, standards were available in the 1880s. As the City developed, so did the guidance for design and construction. Today, we have comprehensive City, State, and Federal regulations to guide design and construction. The area of the City you live in used the regulations in place at the time it was developed. You can view the StoryMap to see what the regulations were for your neighborhood.
The extreme storm events in 2018 shed light on the deficiencies of the City’s stormwater drainage system. Many areas of the City experienced devastating flooding. This prompted the City to begin a comprehensive watershed study program in 2019. The intent of the program is to study each of the City’s watersheds one-by-one. The studies will help us to understand the causes of flooding. The studies will also provide recommended solutions to reduce the risk of flooding.
The watershed studies result in a list of proposed mitigation measures. Once constructed, the measures will reduce the risk of flooding to specific areas of the City. These mitigation measures are generally very costly. Due to limited stormwater management funding, all the mitigation measures cannot be implemented at one time.
The average Stormwater Utility Capital Budget each year is approximately $12 million. Within that, an average of about $2.4 million is used for flood mitigation. As of late 2021, recommended flood mitigation measures for the first five watershed studies were identified. The total cost from the first five studies is approximately $125 million. We expect the remaining 17 watershed studies will have similar flood mitigation project needs. Implementation of these flood mitigation measures will take many decades.
The Stormwater Utility funds the stormwater management for the City. This includes the construction, operation, and maintenance of the entire stormwater drainage system. The Stormwater Utility rates are set each year consistent with Wisconsin Statute. § 66.0821(4) and as described in Madison General Ordinance section 37.05 . These rates are under the purview of the public service commission. The rates are required to be deemed “reasonable” to comply with state statute. During the annual budgeting process, the City tries to balance the stormwater needs with the stormwater rate charged to its customers. These needs include:
- Implementation of flood mitigation measures
- Replacement, extension, and upgrades of existing the existing stormwater system
- Mandated water quality needs and requirements
When possible, the City attempts to get grant funding to partially fund the flood mitigation measures. Grant funding makes up a small part of the funding needed for stormwater management.
The City has created a draft prioritization process. This process creates a proposed order to construct the flood mitigation measures. This process accounts for many factors including:
- Impact on emergency services,
- Location of vulnerable populations,
- If the project also improves stormwater quality,
- Whether other projects are occurring nearby, and
- If outside funding is available.
- City of Madison Flood Website
- Flash Flooding Resilience Story Map *Note: Please view the story map using Firefox or Google Chrome browsers. Story maps are not viewable with Internet Explorer.
- Watershed Frequently Asked Questions
- Engineering Waterways Newsletter 2020 Issue
- Watershed Studies 2019 Audio Presentation
- Flood Prevention Flyer and website
- Everyday Engineering Podcast Episode: Basement Drainage
- Everyday Engineering Podcast Episode: Historic Flooding
- Everyday Engineering Podcast Episode: What's going on with the Watershed?
If anyone has experienced flooding, and is willing to share with the City, please report it on the City's website. Even if a homeowner reported flooding to 2-1-1, FEMA, or a City official, the City needs standardized information to create stormwater models that show existing flooding conditions. The flood data helps the City prioritize different flood projects and future watershed studies. Please report any flooding you’ve experienced.