Behind baseball fields and backyards, researchers evaluate large woody debris for restoring urban streams
By Allie Fehr
Cincinnati, OH — At the end of the Bechtold Park parking lot, two University of Cincinnati students gear up. While local families lace up their cleats for baseball games at the small city park, Peter Grap, a second-year graduate student in Biological Sciences, and Jade Walson, who recently completed her undergraduate degree in Biological Sciences, pull on rubber boots. Tucked behind the trees that line the park’s walking trail lies Cooper Creek, the destination for the pair on the humid June morning.
Carrying the smell of bug spray and sunscreen along with them, Grap and Walson slosh their way through the stream. They are no strangers to the territory as they have been making their way to Cooper Creek three to four times per week since September 2021.
The journey stops when they reach a man-made bundle of branches and wood stretched across the creek. Resembling a miniature beaver dam and built with as much strategy, the structure is one of the experimental sites for a research project assessing the potential of large woody debris (LWD) — logs, trees and branches that fall into streams — as way to improve habitat and water quality in urban headwater streams.
Funded by the Ohio Water Resources Center, the project was conceived by principal investigators (PIs) Dr. Michael Booth, Visiting Assistant Professor at the University of Cincinnati, Dr. Steve Matter, Associate Professor of Biological Sciences at the University of Cincinnati, and Adam Lehmann, Stream Conversation Program Manager with the Hamilton County Soil and Water Conservation District. Along the way, Grap was recruited as a research assistant while Walson and a few other undergraduate students were hired as field technicians to assist with sample collection and processing.
Located in the Mill Creek Watershed, Cooper Creek may look nothing but ordinary to the common eye. Underneath the surface, however, it suffers from high sedimentation — the process in which particles settle to the bottom of a body of water — and lack of aquatic habitat for organisms.
The stream’s urban location can be named the culprit for creating these issues. Surfaces made from asphalt do not absorb water as well as soil does, causing excessive rainfall runoff into bodies of water. Since a forest was originally meant to define the area surrounding Cooper Creek rather than a mall parking lot, the water level rises rapidly in the creek during a rainfall event, and the high velocity of the water erodes the stream’s bed and banks, Grap said.
The increased sedimentation and high velocity of the water pose challenges to fish and insects in the creek. Grap said the insects who make up the base of the food chain may be swept off rocks by the swift water movement, and the buildup of sediments in the water due to erosion limits the deep pool availability for fish.
Although engineered channel restoration can be effective at rehabilitating streams, the high cost and habitat disturbance from these projects prevent them from achieving desired results at a watershed scale, Grap said. Instead, the group of researchers has turned to LWD as a low-cost management practice.
As mentioned in the project’s progress report, log jams — a naturally occurring event in which large pieces of wood accumulate across sections of rivers or streams — are thought to control erosion, retain fine sediments and provide resources for organisms in the stream. Over the years, this wood has been intentionally removed or washed out of urban streams, so the team has introduced new, experimental LWD structures in sections of Cooper Creek in hopes that the restoration will promote channel stability and improve stream habitat.
On this day, Grap and Walson are conducting cross-sectional surveys at fixed locations in Cooper Creek to measure changes, such as increases or decreases in the depth and width of the stream, to assess the effectiveness of the installed log jams in producing new pool habitats. Other measurements the team takes on a given day in the field include tracking the movement of wood and sediments in the stream to evaluate the stability of the log jams.
Thanks to a phenomenon known as “urban stream syndrome,” issues such as erosion and sedimentation are not unique to Cooper Creek. Practically all urban streams show the same signs of degradation, Grap said. Based on their findings, the team plans to use Cooper Creek as an accessible example and recruitment tool to extend LWD installations onto private land in the Cincinnati metropolitan area.
Although funding from the Ohio Water Resources Center for the project ends in August 2022, the team plans to continue their research beyond the deadline. Grap said they hope to see the long-term effects of implementing the LWD structures, such as fish returning to the habitat.