Milwaukee Harbor Breakwater Fish Habitat Demonstration Project

Milwaukee, Wisconsin, United States

The Milwaukee Harbor Breakwater Fish Habitat Demonstration Project—the breakwater is a rubble mound structure built to protect Milwaukee Harbor—was developed as part of an approach that focuses on broadening the environmental, economic, and social benefits that structures can provide. The benefits can be easily integrated as part of ongoing maintenance or new construction activities. The project was designed by the Wisconsin Department of Natural Resources (WDNR) in coordination with the U.S. Army Corps of Engineers (USACE) Detroit District (LRE) and completed in 2014. The design consisted of a five-hundred-foot-long by ten- to fifteen-foot-wide fish habitat that was built using smaller stone than what is typically used for maintenance projects. This project was intended to help planners determine whether suitable habitat can be created as part of the harbor breakwater by making simple, low-cost modifications to the design of the rubble mound used to repair the structure.

Article cover: The large six-to-ten-ton stones used for repairs appear above the water level in this photo of the Milwaukee Harbor side of the breakwater after repairs had been completed on this section. (Photo by ERDC)

Producing Efficiencies

The modified breakwater design includes incorporation of a gently sloped spawning bed of stone topped with cobble on the harbor side of the structure. The modified design is providing a means of increasing habitat availability for various native fish species—thus contributing to long-term sustainability of these species.

Using Natural Processes

Modifications were made to the project design through selection of stone size and slope of the built structure. The design was modified to produce a gentler slope to create fish spawning beds on the interior (harbor) side slope of the rubble mound repair. The heterogeneity of the selected stone sizes and variation in elevation are more reflective of natural reefs, and the new design is intended to serve as a spawning bed for lithophilic spawning fish such as walleye, lake perch, and smallmouth bass.

Close-up photo of the smaller stones placed underwater; the stones were integrated into the repair design of the Milwaukee Harbor breakwater to serve as fish habitat.

(Photo by ERDC)

Broadening Benefits

The demonstration is attracting native fish back to the harbor, leading to increased recreational fishing opportunities and direct support of the local economy. The demonstration is also supporting plans for using a similar approach in other Great Lakes locations, further contributing to restoration of native fish species throughout their historical territory.

The fish habitat was incorporated into the repair design on the harbor side of the breakwater to reduce impacts from wave action from Lake Michigan.

(Photo by ERDC)

Promoting Collaboration

There is a distinct lack of fish habitat in Milwaukee Estuary in general and in Milwaukee Harbor in particular, although such habitat was present historically in the estuary. For this reason, there was keen interest and willingness by the WDNR to work closely with USACE engineers to redesign the breakwater repair to create fish habitat.

Working closely with the Wisconsin Department of Natural Resources, the appropriately sized stone was identified for inclusion in the breakwater repair to attract a variety of native fish.

(Photo by ERDC)