Menomonee River

Menomonee River Flood Management

The Menomonee River Watershed spans approximately 136 square miles across Washington, Waukesha, and Milwaukee counties. The river originates in the Village of Germantown and the City of Mequon. From there, it flows in a southeasterly direction for about 32 miles before it meets the Milwaukee and Kinnickinnic Rivers in the Milwaukee Harbor Estuary. Nearly half of the watershed is covered by urban development—parking lots, roads, rooftops, and other impervious surfaces that prevent water from soaking into the ground. During storms, this runoff rushes into streams, raising water levels quickly and increasing the risk of flooding.

MMSD provides flood management services within the designated service area shown on the map. This area is outlined by a highlighted boundary to indicate where MMSD is able to implement flood management projects.

Problem

For decades, concrete-lined channels and undersized culverts were commonly used to move water quickly through the watershed. Severe flooding in 1997 and 1998 exposed the limits of these approaches, damaging commercial, industrial, and residential properties along the Menomonee River and its tributaries. These aging systems created new challenges:

Higher flood risk
Lost fish and wildlife habitat
Poor water quality
Public safety concerns during storms

Solution

In 2003, the MMSD Commission approved the Menomonee River Watercourse Management Plan, developed in collaboration with regional and local partners. In MMSD’s service area, the plan identified 13 flood problem areas along the Menomonee River and its tributaries and recommended targeted projects to reduce flood risk for hundreds of structures and the communities within the watershed. Completed projects within the Menomonee River Watershed have removed 277 structures from the one percent annual probability floodplain, while there are an estimated 127 structures remaining within the one percent annual probability floodplain.

MMSD has continued working with partners to refine, design, and implement flood management projects throughout the Menomonee River watershed, incorporating these recommendations into broader watershed planning efforts to better reduce the risk of flooding and protect communities.

Menomonee River Concrete Channels

In the 1960s, portions of the Menomonee River and its tributaries were lined with concrete or routed through long culverts to move stormwater as quickly as possible and reduce flooding. The concrete channels created fast, often dangerous flows, creating safety concerns for nearby residents. Additionally, decades after portions of the river and its tributaries were channelized, many of them fell into disrepair, and many residents viewed these sections of the river as drainage ditches with no connection to the natural waterways that flow into Lake Michigan. MMSD and partners have since worked to remove 2.1 miles of concrete lining from the river and its tributaries as of 2025. To restore the natural flow of our waterways and to manage flood risk and improve environmental health, MMSD and partners plan to remove 10.4 miles of remaining concrete lined channels.

concrete lined river channel in milwaukee

Underwood Creek before concrete channel removal

Underwood Creek after concrete removal

Restoring the Natural Flow

Importantly, restored streams absorb and slow down the increased flows after storms, reducing flood and safety risks. Connecting a stream to its floodplain gives the swollen river an area to spread out, reducing flood risk and helping recharge groundwater.

Restoring the natural flow of streams and rivers also improves water quality. Water flowing through riffles, eddies, and meanders not only slows the velocity of the river after storms but also helps to filter pollutants, sediments, and nutrients out of the river. The vegetation along the shoreline of the naturalized streams helps to stabilize banks, preventing soil erosion and reducing runoff and sediments from entering the stream.

Naturalized rivers also create a variety of habitats for fish, amphibians, insects, and other wildlife. As part of the work on the Milwaukee Estuary Area of Concern (AOC), MMSD and partners have developed several low-flow fish barrier projects within the Menomonee River Watershed to allow fish to move more freely for migration.

Menomonee River Watershed Watercourse Plan Highlighted Projects

Honey Creek: In partnership with the U.S. Army Corps of Engineers, this project will remove approximately 4,960 feet of concrete-lined channel, naturalize the stream, and restore portions of the stream bank.
Honey Creek McCarty Park: Designing and developing improvements to reduce flooding risks related to debris accumulation at the trash racks at the entrance to the twin box culverts.
Milwaukee County Grounds: Construction of a floodwater detention basin that covers about 65 acres and holds 315 million gallons of water. Completed in 2011.
Hart Park and Western Milwaukee Levee System: Construction of the Hart park levee (completed in 2007) and the Western Milwaukee Levee system: the construction of a levee, daylighting of Schoonmaker Creek, construction of a 1200-foot-long floodwall, and restoration of banks along the Menomonee River.
Valley Park Levee: Construction of a seven-foot-high and 800-foot-long levee and a five-foot-high, 750-foot-long floodwall. Completed in 2001.
Underwood Creek Naturalization: Removal of approximately 4,400 feet of concrete channel and replacing it with a more natural bioengineered channel to reduce flooding and promote improved water quality and wildlife habitats.

In 2007, Hart Park was expanded from 20 to 50 acres, creating space for floodwater to temporarily spread out during large storms.

MMSD Flood Management Work

Kinnickinnic River Flood Management Projects