East Isthmus and Yahara River Watershed Study

Last Updated: 10/16/2020

Latest Update 

An update will be posted when available.

Project Overview

The City of Madison will complete a watershed study in the East Isthmus and 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

*Note: Please view the story map using Firefox or Google Chrome browsers. Story maps are not viewable with Internet Explorer.

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.

Project Schedule

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 Involvement

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

Public Information Meeting No. 1 was held virtually Aug. 26, 2020.
Aug. 26, 2020 Public Information Meeting No. 1 PowerPoint Presentation
Aug. 26, 2020 Public Information Meeting No. 1 Recording 

Following the presentation, participants had an opportunity to break out into smaller “focus groups” to discuss neighborhood-specific flooding issues. If you are unsure which neighborhood you live in, you can search your address in the top left corner of the neighborhood look-up map. The non-interactive map showing the 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
If you don’t have access to a computer or smart phone, set up an appointment to use computers to view the presentation at a City of Madison Library, or at the UW Memorial Library. You can also register online and receive a phone number to dial into the meeting from any phone. Additionally, you can set up a time to view the recorded presentation on a library computer once the presentation is posted (a few days following the meeting).

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