Turning Coastal Infrastructure into Habitat

By Kevin Bunch, IJC

tern decoys
Common tern decoys are used to attract birds to an artificial nesting habitat near Ashtabula, Ohio, on Lake Erie. Credit: US Army Corps of Engineers

The US Army Corps of Engineers (USACE) has counted infrastructure maintenance as one of its duties for decades, and in recent years looked for ways to use maintenance and repair projects to improve habitat for species in the Great Lakes basin. Collaboration with the Canadian government and conservation groups has been a key factor.

The Corps doesn’t build many new structures these days, said Burton Suedel, research biologist with the USACE’s Engineer Research and Development Center-Environmental Laboratory in Vicksburg, Mississippi. In 2010, the Army Corps started looking into ways to better engineer existing structures to improve ecological, social and economic benefits, Suedel said.

“We’re looking at ways we can take advantage of using nature to utilize operational efficiencies, and we’re also trying to identify ways we can get additional benefits with our infrastructure,” Suedel said. The program was dubbed “Engineering With Nature,” as opposed to traditional “engineering against nature” projects, he added. Those older projects might include surveying canals and building up harbors along the shoreline.

Fish Spawning

Most recently, the USACE has replaced manually operated gates with automated ones in the Soo Locks. This gives operators finer control of water flow over the Main Rapids in the St. Marys River. While the gates on the Canadian side will continue to be manually operated, fine-tuning the flow with the automated gates should now be possible. Lake Superior State University has monitored the rapids over time to see which fish are using the rapids and in which ways, which is helpful data to avoid drowning or scouring fish eggs while adjusting the water flow. Suedel said recent workshops with local experts on both sides of the Canada-United States border are helping gate operators figure out the best way to assist with navigation and improving the existing “world class fishery.”

The Detroit ACE district is working alongside Environment and Climate Change Canada (ECCC) to develop a bi-dimensional Integrated Ecosystem Response Model, or IERM2D, for the rapids, said Jean Morin, hydrology and ecohydraulic section chief with ECCC’s National Hydrological Services. Similar models have been developed for other waterways, including the St. Lawrence River and the Rainy-Namakan Lakes system in Ontario and Minnesota.

“The goal is to optimize the gate opening for fish spawning purposes, in order to select the right timing and the right velocities for ensuring an optimal reproduction success,” Morin said.

The Army Corps provided a baseline hydrodynamic model, which ECCC ran with a variety of variables that change based on the amount of water being discharged and to what degree the gates are opened, Morin said; these include water depth, velocity, turbulence, the slope of the river bottom and current directions.

While ECCC didn’t have much biological data on the rapids, they have experience with species that reproduce in swift-moving rapids environments, like lake sturgeon, lake whitefish and walleye, Morin said. His agency was able to use that data to produce the IERM, analyzing a number of gate opening scenarios to see how it could be used and for what purpose. Their final report is expected this fall.

The first Engineering With Nature project in the Great Lakes took place in Cleveland, Ohio, around 2012. The USACE was interested in repairing a rubble mound breakwater in the harbor – a structure designed to protect harbors, beaches and navigation channels from wave action and sedimentation movement – using large concrete blocks around 9-10 tons each to anchor the repair. Additionally, the Corps wanted to create more habitat for benthic macroinvertebrates and algae – species near the base of the food web. This in turn would create more food opportunities for small fish higher up on the web. The USACE added grooves and dimples to the concrete blocks, as their research suggested that would create more diverse habitat for the species they were targeting. The Corps contractor built a mold that would allow them to do this with other projects, he added.

Gulls and Shrimp

Following Cleveland, the Army Corps worked on a similar project in Ashtabula, Ohio, and was able to reuse molds from the Cleveland project. It also contacted local agencies and other stakeholders like The Nature Conservancy to see if there were any other benefits they could add.

“We reached out (to those groups) up front to ask them specific questions about what habitat is lacking in the area, and is there any way we can incorporate that habitat into the redesign of the breakwater?” Suedel said.

Those organizations noted that the common tern had lost nearly all its nesting habitat in that area due development and competition by gulls. While suitable habitat existed kilometers distant east and west along the coastline, Suedel said terns lacked the sandy habitat they preferred on Lake Erie around Ashtabula. Concrete blocks were modified to include suitable habitat in a detached breakwater for the birds. The success of that project is still being monitored, though a 2016 winter storm damaged the site and required repairs during the nesting season.

Also in 2014, the USACE Detroit District’s floating plant crew took up the task of rubble mound repairs in Milwaukee, Wisconsin’s harbor breakwater area. It contacted Wisconsin Department of Natural Resources (DNR) fisheries biologists to find out what that harbor was lacking, and they suggested using smaller stones for the breakwater repairs that fish could spawn on, Suedel said. The Wisconsin DNR helped design the repaired section, which was 500 continuous linear feet along the breakwater, with funding from the US Great Lakes Restoration Initiative.

The University of Wisconsin-Milwaukee has taken on monitoring duties in the harbor.

University of Wisconsin-Milwaukee ecologist James Janssen said they’ve discovered that the Corps has created a rare, cave-like habitat between the large breakwater boulders and the smaller rocks that nonnative bloody red shrimp (Hemimysis) are thriving in.

The shrimp are providing a major local food source for a variety of fish species, including largemouth bass, smelt, rock bass, alewives, and brown trout. Alewives and smelt typically prefer living in the open waters, but Hemimysis are drawing them closer to shore as invasive quagga mussels have reduced the amount of food available in the open lake. Janssen said this should not suggest that Hemimysis be introduced into inland lakes as a food source, however, as conditions vary in harbors.

The spawning side of things is a mixed bag. Janssen said silt coming down the Milwaukee River appears to be drowning eggs in the spring, suggesting that efforts upstream to limit sedimentation might improve spawning grounds. Those that hatch have a ready food source from the Hemimysis, but have to avoid getting eaten by the larger predatory fish in the area.

Partnerships

Janssen said since conditions are different in other harbors throughout the Great Lakes, the work in Milwaukee can’t be used as a guide or an example for other sites. A final report is pending from the USACE. But Janssen said knowing enough about local physical and biological conditions can provide information to predict which species will dominate at a breakwall, and a preliminary study before doing any modifications can help clarify that prediction further.

milwaukee harbor breakwall
The Milwaukee Harbor breakwall modifications under construction in 2014; once completed the water level rose to where the line is drawn and the larger boulders submerged. Credit: John Janssen

“Our key to success is reaching out to stakeholders and identifying which habitat would be most appropriate for us to create,” Suedel added. The USACE didn’t do that in Cleveland since it was focused on the base of the food web, but for other species it has proven successful, he said.

The USACE also is interested in public-private partnerships to help fund restoration projects. While Great Lakes Restoration Initiative funds and money from the Army Corp’s Engineering With Nature initiative have been used for the projects so far, partnerships could help provide outside funds for monitoring and additional construction. He said Milwaukee Harbor is one area that would benefit from funds for additional fishery habitat along other portions of the breakwater.

“It was a relatively modest $20,000 increase over the cost of repair in Milwaukee’s (breakwater) in 2014,” Suedel said. “If we can’t identify that money internally, can one of our stakeholders help fund that additional cost? So that’s that where public-private partnerships could come in handy.”

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.

automated gates
The automated gates project in the St. Marys River’s compensating works structure should help fine-tune water flows to the Main Rapids, preventing fish eggs from being scoured or left out to dry. Credit: US Army Corps of Engineers

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