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The City of Madison Engineering Division is sharing a new, interactive map and tool for the community to learn more about flooding impacts, stormwater infrastructure and potential flooding in the City of Madison.

The Watershed Study Flood Risk Map allows a more detailed look at specific locations, down to the street level, to see how much water the stormwater system can handle, and if the stormwater system is meeting some of the City’s stormwater management targets.

This mapping is a result of the City of Madison Engineering Division’s watershed studies, which were launched in 2019 after historic flooding devastated the City in August 2018. The watershed studies focus on how stormwater drainage system can be improved to support heavier, and more frequent, rain storms. 

A watershed is an area of land where precipitation that falls on it, drains to a common waterway, such as a stream or lake. The watershed acts like a funnel by collecting all the water within the area and channeling it to a single point.

Understand the map
Deep water shown on the map doesn’t necessarily mean that there is an issue. For example, when looking at the map, if deep water is shown in a channel, that is appropriate, because that is where Engineering designs the water to go. However, if deep water is shown directly next to a building, that may mean the stormwater system in that area is not able to handle heavier storms, and that the building, roadways or property may be more prone to flooding.

In areas where flood risk mapping from watershed studies is not available, the map shows areas that the existing soil suggests that the area flooded in the past. This information is less accurate and less reliable and will be updated with more detailed flood risk data as more watershed studies are complete.

These maps were created using stormwater models that have been calibrated to real world conditions and represent a reasonable estimate of existing conditions.  However, users of this map should keep in mind that this map is based on a model and is only a representation of real world conditions. Specific conditions at any exact location may alter the expected flood depths beyond the ability of the model to estimate. 

Watershed progress
City Engineering launched its watershed studies in 2019, and there are three main phases:

  1. Data collection
  2. Flood map sharing
  3. Solution evaluation

City Engineering is holding three public information meetings for each watershed, which shares data the City collected, asks for feedback and shares solutions based on information gathered from the public. Modeling of the stormwater runoff within the watersheds are undertaken for each watershed studied.  The Flood Risk Map will be updated as the runoff models within each watershed are completed.