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The Dynamism of the Chicago River

The Chicago River has always been dynamic, with floods occurring multiple times a year.  The level of the river fluctuates as much as eight vertical feet in some years.

Long before skyscrapers lined its sides, the Chicago River was a marshy stream. The first transformation of the river occurred in the 19th century when it was contained within the walls of an engineered channel, and the flow of the river reversed to improve sanitation. These moves supported the industrial transformation and incredible growth of the city. However, in the time since, the high walls of the channel as well as heavily polluted waters, discouraged Chicagoans from descending to the river’s edge to experience the dynamics and ecology of the river.

Today, the river has again been transformed—its waters flowing clearer and its shores supporting a new stretch of public space providing communal access to the water’s edge. Achieving this level of access meant the design would be subject to periodic river flooding. The design of the walk itself is terraced down to the water’s edge, allowing higher portions of the riverwalk to remain dry and accessible during minor flooding events. Durable paving materials were used and marine-grade lighting fixtures installed to withstand water inundation, and plant species were selected that tolerate periodic saturation with river waters. Overall, every design element had to contribute to an environment that could easily be cleaned up following a flood event, and reopened to the public as soon as possible.

Just weeks after the opening of the Riverwalk, a record flood (shown in the photo above) put these resilience strategies to the test. Sasaki’s design passed with flying colors—the Riverwalk was cleaned and reopened within 12 hours of the waters subsiding.

Sometimes the greatest designs are nearly invisible, as is the case when resilience strategies become seamless with an experience of pleasure and functionality. However, at the Riverwalk many of the features that make the design resilient and support river ecology are in fact are not left to be backstage heroes, but brought forward as stars of the show.

Sections of the Riverwalk between bridges were created as distinct rooms, six rooms total corresponding to the six blocks along the river from State Street to Lake Street. The Jetty (Wells Street to Franklin Street) in particular is dedicated to educational elements and ecological experimentation. Here seven piers jut into the water at irregular angles and are anchored to fixed guide piles and mark the current level of the water, showcasing the dynamic range of the river. In between the piers are floating wetlands and water gardens planted with a number of native and water tolerant species, including sedges (grasslike perennials), irises, cardinal flowers, swamp milkweed, and others, harkening to the river’s marshy past. The floating garden plants feed upon nutrient-rich water and in their first full year were already thriving, attracting monarch butterflies as well as herons as shown in the below photographs. The native plant selection is also important as these need to be species that can survive and flourish in an environment that is sometimes inundated with water.

Perhaps what’s most impressive in the design of the Riverwalk is what is beneath the surface. Underneath the docks at the Jetty there are habitats designed to support aquatic life. Using very low-cost materials, such as steel mesh screens that support barnacle growth and shredded nylon ropes that support algae formation, as well as perforated steel cylinders termed ‘lunkers’, these create places where fish can hide out and take rest from the river current. Working with fish ecologists, the designers went as far as to understand what species of underwater creatures preferred to live at what depths, and so arranged the underwater habitats to reflect their preferences. The gravel trays that house water lilies and other floating plants, also support insects, and their roots hanging into the water create what is called a biofilm that supports the life of aquatic organisms such as zooplankton– creating vital sources of nourishment for fish.

This design built off of the great work done by the Friends of the Chicago River and team that had put what they called a “fish hotel” as an experimental structure into the Chicago River from 2005-2012. Their experimental research took the first step in proving that it is possible to build a viable fish habitat within the main stem of the Chicago River, and the design team built off of what they’d accomplished to take the design for the Riverwalk further. One of the ways our team took the experimentation further was to use the design opportunity to test different substrate materials. Where constructions designed to support riverine or marine life are often made from concrete, this habitat design incorporates soft and more complex surfaces–such as the nylon ropes full of nooks and crannies– as a way of testing the idea that these surfaces might prove to be better substrates for sessile or fixed organisms, such as mussles, to make their home.

This year, a faculty-student research team from The Illinois Institute of Technology has partnered with the Landscape Architecture Foundation to perform a Case Study Investigation on the success of the Riverwalk’s unique landscape strategies. Their research will be released in August of this year, and we hope the data that their study produces will help to validate the ecological benefit of these strategies. “When people see this part of the Riverwalk, their really getting frames and snapshots of what had been there long before,” says Anthony Fettes, former Sasaki ecologist and current Professor of Landscape and Urban Ecology at the University of New Mexico, whose research was essential to the project.

The design of the Jetty serves as an outdoor river life classroom and embodies a philosophy that sustainability addresses more than just human needs in the environment. Together the floating wetlands and the constructed fish habitats support a surprising flourishing of river ecology even in the midst of a heavily urbanized environment.

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