EVALUATING RESTORATION EFFECTS ON TRANSIENT STORAGE AND HYPORHEIC EXCHANGE IN URBAN AND FORESTED STREAMS
OSYPIAN, Mackenzie L., Civil Engineering, University of North Carolina at Charlotte, Charlotte, NC 28262, email@example.com, JEFFERSON, Anne J., Department of Geology, Kent State University, 221 McGilvrey Hall, Kent, OH 44240, and CLINTON, Sandra, Department of Geography and Earth Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223
Millions of dollars are spent each year on restoration projects designed to improve stream habitat, but few studies have investigated effects of restoration on hyporheic exchange and transient storage. Stream water-groundwater interactions and transient storage in four second-order streams (urban/forest; restored/urestored) were studied by measuring geomorphology, streambed vertical head gradients and water fluxes, and by using conservative, impulse-loaded tracer studies along with the OTIS model. The magnitude of upwelling and down welling was observed to be greatest in the restored urban stream, which contains large step structures, while the smallest gradients were observed in the unrestored urban stream, which is incised to bedrock. OTIS results show that the 120 m unrestored urban reach with a debris dam has an average transient storage of 1.8×10^-2 m2/m and an ? of 9.5×10^-4 s^-1 while a 55m restored forested reach with log sills has an average transient storage of 8.3×10^-2 m2/m and an ? of 1.5×10^-4 s^-1. Based on these results, we conclude that restoration changes transient storage metrics, and ongoing work aims to understand how these changes affect ecosystem health.
Some of our students are in the field this week, injecting Cl- and Br- into a restored reach and an unrestored reach in tributaries of Beaver Dam Creek. Our goal is to understand the role of wood jams versus restoration structures in promoting stream-hyporheic exchange.
In the photo are Alea, Xueying, and Mackenzie. Photo by Brittany. They’ve got it so capably handled they didn’t even need Sandra or I out there with them today, but I’m going tomorrow for an excuse to be in the field as much as anything.
Note: This post is a collaborative effort by Anne and guest blogger Will Dalen Rice, a graduate student in the Department of Geography and Earth Sciences at UNC Charlotte. He had the misfortune of taking a couple of courses from Anne this semester and has become a certified stream junkie, going out on rainy nights to see how high Charlotte’s urban streams are running.
Most cities were started around the idea of available surface water resources. Development and misuse of our streams (ex: “dilution is the solution to pollution”) has resulted in the modern urban stream. These streams are straight and good at carrying storm water, full of sediment and pollutants, and they lack good habitat for plants and animals. Now that we are beginning to notice how degraded and trashed these city waterways are though, scientists and engineers are beginning to attempt to address the form and function of these waterways to hopefully return them to a more “natural” (or at least aesthetically pleasing) state. While there are many stream restoration techniques, they often involve mechanical manipulation of the stream channel and banks and the planting of riparian plants along the stream corridor. As the streamside ecosystem redevelops, the idea is that health of the stream will also improve (leave it to nature to clean up our messes, given the chance).
For large urban streams, the standard practices in stream and habitat restoration are sometimes not possible, often because decades of infrastructure development have pinned the stream into a narrow corridor. So other approaches need to be considered, and Robert Francis and Simon Hoggart of King’s College London discuss ways that existing artificial structures can be put to work to mitigate some of the ecological impacts of urbanization. In the specific case of the River Thames in England, habitat development has been observed on man-made structures, and furthermore, certain types of man-made structures grow life better than others. Francis and Hoggart show that indeed plants (and therefore animals) can develop in a riparian zone better when brick and wood and rougher materials are used over concrete and steel. If concrete and steel already exist, adding brick and wood can further trap sediment for habitat growth (like gluing a cup of dirt to a steel wall). They suggest that this should become standard practice when thinking of restoration efforts in large, urban waterways.
The NOAA’s Northwest Fisheries Science Center says Thornton Creek in downtown Seattle exemplifies “the challenges facing rehabilitating urban streams.” But a look at the NOAA picture below shows that this stream is also emblematic of a riparian ecosystem that has developed within the constraints of the existing structures and maybe even a spontaneous model for the sort of restoration that Francis and Hoggart envision.
Francis, R., & Hoggart, S. (2008). Waste Not, Want Not: The Need to Utilize Existing Artificial Structures for Habitat Improvement Along Urban Rivers Restoration Ecology, 16 (3), 373-381 DOI: 10.1111/j.1526-100X.2008.00434.x
An opportunity to do graduate work at UNC Charlotte with excellent and enthusiastic aquatic biogeochemist Sara McMillan:
We are seeking qualified applicants for a graduate assistantship at the MS or Ph.D. level, starting in the summer or fall of 2010 (summer preferred) in Dr. Sara McMillan’s laboratory at the University of North Carolina at Charlotte. Our work broadly addresses the interactions between ecology and biogeochemistry in aquatic ecosystems. This position is funded through a collaborative project with Dr. McMillan and Dr. Greg Jennings at North Carolina State University investigating the impacts of stream restoration on nitrogen dynamics in urban streams. Field and laboratory experiments will focus on reach-scale nutrient retention, microbial biogeochemistry (i.e. denitrification and nitrification) and microbial diversity. Opportunities exist to develop research aims that align with the project for the individual research. Preferred qualifications include a strong background in biology and hydrology, experience with field and laboratory research, and good teamwork and communication skills. The position is funded for 1 year at $18,000 with possibilities for future funding.
If interested contact: Dr. Sara McMillan (firstname.lastname@example.org) for more information.