A series of dams has divided the Des Plaines River for more than a century, blocking its natural flow as it meanders its way from Wisconsin through northeastern Illinois.
The dams soon will be gone, targeted by engineers, scientists and conservation officials as a way to restore the 133-mile waterway to its natural flow.
Two dams near Vernon Hills are scheduled to come down this summer. Six dams already have been removed from the river since 2011, and additional structures are slated for demolition in Cook County in the coming months. Once the collection of demolition projects is complete, the river, which cuts through many of Chicago’s suburbs, will flow freely for nearly its entire length.
The dam removal projects, experts say, benefit both humans and the habitat, especially the fish, insects and plant life that depend on the water-based ecosystem to thrive.
The biggest winner is the river itself.
“Frankly, this is nationally significant,” said Steve Pescitelli, a stream specialist with the Illinois Department of Natural Resources.
Low-head or run-of-river dams have been causing a cascade of environmental problems for decades, according to scientists. The barriers impede the river’s flow, hurt water quality and aquatic life, stifle fish migration and the surrounding ecosystem in addition to causing safety hazards for people paddling and fishing.
Initially built for agricultural, aesthetic or sanitation reasons, the dams outlived their purpose and negatively affect the river and the environment, scientists and advocates said. These dams do not provide flood control or relief, engineers and scientists said, so that is not a reason to leave them in place.
“I think restoring the river to its free-flowing condition is a benefit in and of itself,” said Eric Otto, a civil engineer with the Forest Preserves of Cook County.
The dam removals on the Des Plaines are part of a trend happening at rivers, streams and creeks from coast to coast, with work picking up during the last two decades. Nationwide, 72 dams were removed from rivers and streams in 2014, according to the nonprofit conservation group American Rivers, opening up 730 miles of waterway. In California, the U.S. Forest Service is launching a project to remove 81 dams on creeks in the Cleveland National Forest southeast of Los Angeles. Other watershed projects are happening in Connecticut, Delaware and Ohio.
“All communities benefit even if they don’t ever see the river,” said Jessie Thomas-Blate, associate director of river restoration at American Rivers. “The river is helping them. Everyone needs clean water. Everyone needs the benefits that rivers provide.”
Before suburban sprawl, the Des Plaines River flowed freely through the prairies and forests of northeastern Illinois.
Most of the dams on the river were built beginning in the 1920s and 1930s. Farmers used the dams for irrigation purposes or as fords to cross the river before dozens of bridges were built to crisscross the river in booming suburbs.
Dams also were used to combat the smells of raw sewage once dumped into the river before modern water sanitation techniques. Deeper water pools masked the smell of decomposing sewage. And other dams were constructed for purely aesthetic reasons, to cover up what some considered to be unsightly mud flats and marshland.
But recently increased awareness of their environmental impact combined with practical concerns formed conditions ripe for agencies to dedicate money for the work. With many dams deteriorating, communities determined it was both cost-effective and beneficial to remove them altogether.
“It’s part and parcel of a kind of environmental advocacy in general, being cognizant of the benefits of nature and restoring the native conditions,” Otto said.
Most of the dams removed from rivers and streams throughout the United States have been demolished in the last 20 years, 971 of the country’s 1,185 dams, according to the American Rivers database.
“The more habitat you reconnect, at least with the ecology, the more benefit you get,” Thomas-Blate said.
Boost for aquatic life
While the paddlers participating in last Sunday’s Des Plaines River Canoe & Kayak Marathon needed to contend with the dams during their trips, the barriers do much more harm under the water.
Fish can’t swim up or downstream. Algae blooms thrive in the oxygen-starved pools above the barrier. The water is stagnant and unmoving, choking off life for the food chain of fish, mussels and insects that call the river and its banks home. Sediment builds up behind the dam. Fish diversity and population numbers suffer.
But when dams are removed, carp, green sunfish, largemouth bass and bluegill all benefit, Pescitelli said. More migratory fish such as channel catfish, sucker species and walleye will be able to move up and down the river, diversifying the entire river.
Taking out dams also helps mussels, freshwater shrimp and so-called aquatic invertebrates, especially mayflies, stoneflies, dragonflies and damselflies that fish feed upon, the building blocks of a healthy ecosystem, scientists said. There are about 70 species of fish in the Des Plaines River, Pescitelli said.
The water itself also gets a boost. Dam removal will help the hydrology of the river, restoring the natural flow and improving water quality. It changes the landscape of the river banks, especially above existing dams, benefiting the soil and restoring a more natural environment.
“There’s a lot of things that depend on the system, and when you divide it with dams, you just cut off the ability of the wildlife to move up and down the river,” said Jim Anderson, director of natural resources for the Lake County Forest Preserve District. “We’re trying to reconnect the stream, both upstream and downstream, and the goal is to reconnect the ecology of the river.”
Once a dam is removed, it does not take long for the river to reclaim its natural path.
Within months, said Rick Gosch, acting director of water resources for IDNR, the ecosystem surrounding the former dam site will reach “some point of equilibrium.” On the formerly submerged land along the river banks, plant life that loves mud begins to return.
After the dam at the Ryerson Conservation Area near Lincolnshire was removed in 2011, studies indicated that fish benefited from the free-flowing water, with certain types of species recolonizing upriver. Fish surveys indicate that current-loving species recolonized the river above the former dam.
“It basically just returns to its natural flow,” Pescitelli said. “It’s very predictable, and it’s very rapid.”
Reconnecting the river
Work to remove the Wright Woods Dam began last year, but crews discovered that the concrete dam included steel pilings that made the project more complicated. Work was delayed, the project was re-bid and work will begin again this summer. The MacArthur Woods (Hollister) Dam upstream also will be removed.
IDNR initially gave $750,000 to Lake County for the dam removal projects. Michels Construction will be paid about $480,000 for the remaining work on the Wright Woods and Hollister dams.
A $10 million state initiative launched a few years ago aimed to remove 12 dams in Cook County.
Five dams on the Des Plaines have been removed so far in Cook County, with three more scheduled to come down by 2016: the Dempster Street Dam, the Touhy Avenue Dam and Dam No. 4, near Rosemont. Dam removal projects also are slated for the North Branch of the Chicago River, and several dams have been demolished on the Fox River.
Removing a dam can be unsettling to some, Pescitelli said, because people worry what the area upstream from the dam will look like when the river returns to its natural course. People are afraid the river will either dry up or flood more often, but neither of those extremes are reality, Pescitelli said. The dams on the Des Plaines River were never built for flood control, Pescitelli said, so their removal will not affect flooding.
“You get this bang for your buck both for fish and for people, the general public too,” Pescitelli said.
If all goes as planned, by the time paddlers participate in next year’s race, the course will be dam-free.
“I think it’s great,” said Jack Snarr, co-chairman of the annual canoe and kayak marathon. “It’ll be a good benefit for users of the river, those out on the river exploring and seeing the sights that they may not otherwise see.”
Snarr said he’s looking forward to a naturally flowing waterway.
“Eventually,” he said, “it will be a wild river again.”
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