future because the flow is manipulated away from sensitive areas. Conversely, riprap and concrete in the stream simply armor the sensi- tive areas. When water hits riprap or concrete, it is moving fast and creates turbulence near the bank. That turbulence can erode adjacent unprotected areas of the bank, causing increased erosion around and downstream of the hard-armored materials. Additionally, research shows that property values increase near water features. Home lots adjacent to wet ponds in Champaign and Urbana, Illinois are worth an average of 21.9 percent more than non-adjacent lots in the same subdivision. A study by Nicholls and Crompton (2017) shows that “significant positive property price effects are associated with river, stream, and canal view and proximity.” Once a stream has been restored to protect infrastructure, adjacent property values will increase. The most sustainable and multi-functional method to protect infra- structure at stream crossings is a restoration. Stream restorations create a stable stream that will provide long-lasting protection of the infra- structure. Restorations have the additional benefits of reestablishing the ecological function of a stream system and reconnecting people to nature, thereby improving their personal wellness. By changing our perspective, we can turn failing infrastructure into an opportunity to create an asset to the community and the environment while protecting the well-being of both. And what about the 33” exposed sanitary interceptor pipe in the Un- named Tributary to the Saline Branch? Farnsworth Group compared several options to protect the pipe and determined the most cost-effec- tive solution was to restore the stream. We adjusted the channel alignment to gently curve the stream away from the threatened manhole, constructed a small bench, or shelf, on the bank to give the stream space to flood, and constructed a series of structures with boulders to direct the flow of water into the center of the channel and away from the bank. We also slowed the water directly upstream of the pipe by creating a slow-moving pool, followed by a long, steep streambed where water cascades and tumbles over large rocks. The banks and floodplain are now planted with native vegetation (Photo 4). The interceptor pipe is now carefully protected underneath the boul- ders of a stream structure. Deer, heron, turtles, and a plethora of fish have been spotted in the park setting, and raccoon tracks can be seen on the stream bank. The sound of running water muffles traffic noises nearby. I watch a dragonfly dart across the water and listen to the bees droning on the bank. The serenity of the stream relaxes and rejuvenates me as I head back to the office to start the next project.
gravel bottom of the channel, which is necessary for ideal fish spawning locations. Vegetation along the banks of the stream provides shade to the stream, which regulates the temperature of the water. Vegetation also provides habitat to pollinators like bees, butterflies, and dragonflies. Dragonflies carry the additional benefit of eating 30-100 mosquitoes a day. Small mammals and birds live and eat in streamside vegetation. A restored stream system can host a diverse bevy of species. For example, one week after the Copper Slough bank restoration project in Champaign was complete, a blue heron was fishing off of the boulder structure in the stream. Fish were enjoying the depth of the scour pool beneath the structure, and dragonflies, songbirds, and butterflies were bountiful in the native vegetation lining both sides of the stream. Birders regularly come to the Boneyard Creek Second Street Basin to watch the migratory birds take refuge in the restored in-stream basin. The Illinois Department of Natural Resources (IDNR) found a fish species called the Largescale Stoneroller in the Kickapoo Creek one year after the first phase of a stream restoration project was completed. The Largescale Stoneroller is classified as a species in greatest need of conservation by IDNR. Increase Property Values Not surprisingly, the biggest argument against stream restorations is the cost in comparison to a less-natural approach, like using riprap or concrete to stabilize infrastructure. Certainly, stream restorations are expensive, but they are also sustainable. Stream restorations have long-lasting, positive effects. With a one- time restoration project, infrastructure is protected for the foreseeable Unnamed Tributary to the Saline Branch post-restoration to protect the 33” sanitary sewer. Photo: Jenkins / Farnsworth Group
EMILY POYNTER JENKINS, PHD, PE, CFM, is a project engineer for Farnsworth Group (www.f-w.com) who has been designing stable and sustainable stream restorations and bank stabilizations for more than 10 years. Examples shown in this article are designs of hers and the Farnsworth Group team. Her clients have included municipalities, utility companies, local developers/builders, and private property owners.
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csengineermag.com march 2020
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