Last Updated: 08/14/2020

Update 8/7/20

A virtual public informational meeting for this project is being held over Zoom on August 26, 2020 at 6:00 p.m. See below for registration information.

Project Description

The City of Madison will complete a watershed study in the East Isthmus & Yahara 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.The City of Madison has hired a consultant, Tetra Tech, Inc to complete the first half of the study where the existing conditions are modeled.
For more information please see the Flash Flooding Story Map.

Map of East Isthmus and Yahara River study area. It extends from east of the capitol to east of the Yahara River.

The East Isthmus & Yahara study area drains primarily to the Yahara River and parts on the far east and west sides of the watershed drain directly to Lake Monona. The study extends west past the isthmus Yahara River watershed because the surface water is connected to an area that drains directly to Lake Monona and it’s important to study both together. The study extends to the east where a part of the watershed drains to Lake Monona because the City anticipates upcoming construction projects in this area, and therefore would like to have the stormwater system studied.


The study is beginning Spring 2020 and is expected to take over 12 months. During this time, the City will look at watersheds as a whole to understand the interaction of flash flooding and the increased risk of flooding due to high lake levels. The East Isthmus and Yahara River watershed study will be done in two phases where a consultant will first develop an existing conditions model and analyze the impact of the Yahara River elevations on localized flash flooding. Following the completion of that work, the City will set up a separate contract for the solutions phase of the study.

Public Information Meetings

Virtual Public Meetings- August 26, 2020 from 6:00pm to 8:00pm. To attend this meeting, you must first register in advance at the link below. Once available, the presentation will be posted prior to the meeting. This meeting will be recorded and will be a public record subject to disclosure. By continuing to be in the meeting, you are consenting to being recorded and consenting to this record being released to public record.

Register for this webinar:

After registering, you will receive a confirmation email containing information about joining the webinar.

Following the presentation, participants will have an opportunity to break out into smaller “focus groups” to discuss neighborhood-specific flooding issues. The map showing the anticipated focus groups is shown below:
Focus groups broken down into neighborhood association groups. 1. Tenney 2. Marquette 3. SASY 4. Emerson East 5. Sherman and Sherman Terrace

Watershed Study Information

To learn more about flash flooding and why the City is completing a watershed study in this area please visit: Flash Flooding Resilience Story Map

To learn more about lake level flooding, which has impacted this watershed in recent years, please visit: Lake Level flooding Story Map

Listen to a presentation about the City's watershed studies at: Watershed Studies 2019 Audio Presentation.

Report Flooding

If anyone has experienced flooding, and is willing to share with the City, please 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 clues of the flood waters extent and depth. Clues include:

  • Debris lines outside (twigs, leaves, dirt are left behind in a line on the lawn, sidewalk, mailbox post, shrub etc)
  • Border of disturbed vegetation—if half the vegetation has been bent or is stuck to the ground in the direction of the flow, you can see the reach of the flood water

Document these clues and measure any depths where debris lines are above the ground. Pictures with descriptions are very helpful. For example:
Images showing debris line on the grass and on the wall of a building
If you were unable to capture any photos, descriptions are also helpful:

  • 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.

Additional Information