Visitors to The Morton Arboretum in November and December will likely start to see something that has been hidden for years: the banks of the DuPage River.
A choking mass of vegetation will be cleared away as part of an ecosystem restoration project, which will stabilize the river’s eroding banks and create habitat for native animals and plants, according to Kurt Dreisilker, the Arboretum’s head of natural resources.
Within two years, the river will have wide, gently sloping banks planted with native grasses and rushes, sedges, and wildflowers such as swamp milkweed, blue flag iris, and New England aster. Over time, the plants will grow tall and their roots will intertwine to hold the soil.
Boulders and other structures along the riverbed and banks will break up the water’s flow, creating niches where fish and other animals can shelter and breed.
“We’re creating little nooks and crannies,” Dreisilker says.
The work will likely start on the West Side, near Arbor Lake, and proceed upstream on both sides of the river. Some nearby trails will be temporarily closed as the work requires; signs will redirect hikers.
The result will be a more attractive, more vital river, while safeguarding important trees.
“It’s an opportunity to restore habitat and at the same time stop erosion that threatens our collections,” Dreisilker says.
The Arboretum and the U.S. Army Corps of Engineers are collaborating on the $5 million project, which takes in a mile and a half of the river, flowing through collections including Ozarks, China, Japan, Elms, Willows, and Walnuts. It is designed to have no effect on flooding.
It will help reduce the unintended effects of long-ago projects that straightened the river to make room for agriculture and urbanization, leaving it with no bends and steep, clifflike banks. In every heavy storm, rushing water scoured the soil from the roots of valuable trees in the collections, causing some to fall into the river. Shrubs and trees, most of them invasive species, grew up along the banks, hiding the stream from view in most places. The river became a difficult place for many species of fish, amphibians, and other plants and animals to survive.
After its banks are regraded to be slopes, not cliffs, the river still will be straight, but it will offer habitat for a much wider variety of species of fish, birds, and plants, with gentle banks that offer views of the water from rerouted trails.
The work involves cutting down many invasive trees and shrubs, such as buckthorn and black alder, that crowd the river banks. In the Arboretum’s collections, some large trees that are too close to the river’s edge must come down too. But important tree species have been transplanted or propagated to be planted in sites away from the river, safe from erosion and free to spread their roots and branches.