Pennito Creek Watershed Study

Project Overview

The City of Madison is completing a watershed study in the Pennito Creek watershed (as shown below). City of Madison engineering staff are completing this detailed modeling effort to 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.

Please note that this project is different than the Pennito Creek Flood Hazard Mapping study being completed by Wisconsin DNR.

For more information please see the Flash Flooding Story Map . *Note: Please view the story map using Firefox or Google Chrome browsers. Story maps are not viewable with Internet Explorer.

The Penitto Creek watershed study encompasses areas draining to Pennito Creek and unnamed tributaries that discharge to Upper Mud Lake near the Beltline and US51 interchange, as well as areas draining to Owl Creek on the southeast side of Madison.

Still have questions? Get some answers here from our additional information page on the Watershed Studies.

Project Schedule

The project kicked off in the spring of 2024 and the study is expected to take 18 - 24 months to complete.

Public Involvement

There are a number of points of contact during this project when the public is encouraged to give feedback as part of public information meetings and focus groups. Dates and times will be publicized and added to this website as the project progresses.

Public Information Meetings

July 25, 2024 Public Information Meeting Recording

July 25, 2024 Public Information Meeting PowerPoint Presentation

Focus Group Meetings

Details for Focus Group Meetings will be posted here when available.

Report Flooding

Anyone who has experienced flooding and is willing to share information with the City is encouraged to report it on the City's Report Flooding Portal. 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.

The key to good reporting is including specific details and visuals.

If it is possible to do so safely, collect the following information when it is flooding:

• Date of the flooding
• Total time flooding occurred
• The time the flood water reached its highest point
• Photos of flooded areas when they are the most flooded
• Videos showing how the water is moving into and out of the flooded area

Once the flood waters have receded, and it is safe to do so, look for indications of the flood waters extent and depth. Indications include:

• Debris lines outside (twigs, leaves, dirt left behind in a line on the lawn, sidewalk, mailbox post, shrub, etc.)
• Border of disturbed vegetation – if an area of vegetation has been bent over or is stuck to the ground in the direction of the flow, you can estimate the extents of the flood water

Document these indications and measure any depths where debris lines are above the ground. Pictures with descriptions are very helpful. For example:

If you were unable to capture any photos, descriptions are also helpful. For example:

• Flood water reached the base of the first step on the front walk of our house at X address.
• Flood water was 12” deep at the mailbox in front of X address

Existing Conditions Flood Mapping

The watershed model is used to evaluate numerous design storm events. The City created an online viewer for the 1% chance (100-yr) storm event and a link to that information will be posted here when available.

Proposed Flood Reduction Solutions

The watershed study will result in 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.

Information will be posted here regarding the proposed solutions when available.

Background

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 in the City. 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 stormwater drainage 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 where you live 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, the mitigation measures cannot all be implemented at one time.

The average Stormwater Utility Capital Budget each year is approximately $12 million. From 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.

Additional Resources

• 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 Study Learning Hub
• Engineering Waterways Newsletter 2022 Issue PDF
• Watershed Studies 2019 Audio Presentation
• Flood Prevention Flyer and website
• LISTEN: Everyday Engineering Podcast Episode: Basement Drainage
• LISTEN: Everyday Engineering Podcast Episode: Historic Flooding
• LISTEN: Everyday Engineering Podcast Episode: What's going on with the Watershed?

Report Flooding

Anyone who has experienced flooding and is willing to share information with the City is encouraged to 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.