The following five Outdoor StreamLab (OSL) projects are currently planned for spring, summer, and fall of 2008. Project details are subject to change. We encourage potential collaborators to contact us about research and educational opportunities at any of the StreamLab facilities.
Project 1 | Project 2 | Project 3 | Project 4 | Project 5
Project 1: Equilibrium topography of a sand-bed channel within a floodplain
Researchers: Anne Lightbody, Jeff Marr, Chris Paola, Gary Parker, Cailin Orr, Jacques Finlay, Peter Wilcock, NCED visitor program participants
Stream restoration projects often seek to improve physical properties and to rehabilitate the ecological processes of a channel; however, project designs are often based on limited scientific knowledge. In this project, researchers designed a sinuous sand-bed channel incorporating the best current knowledge of equilibrium channel properties. Various methods of channel design were compared, including stream restoration manuals and comparison to existing sand-bed streams. The predicted river slope matched observations. In addition, during the first season, the river reshaped its initially flat bed to create point bars on the inside of meander bends. In the long term, a river within an erodible floodplain will sculpt its banks to create dynamic equilibrium (that is, although any position along the channel may change, the channel’s mean properties will remain constant). Monitoring of bank and bed topography will continue throughout the life of the OSL.
Project 2: Dominant control of cross-stream super-elevation within meander bends
Researchers: Kyle Straub, Chris Paola, Anne Lightbody
The cross-stream water elevation profile within meander bends is typically sloped, so that the water elevation at the outer bank is elevated above that of the inner bank. This slope creates a helical secondary circulation cell, which moves flow across the river bed toward the inner bank and builds point bars at the inside of meander bends. In the OSL, researchers found that the secondary circulation cell is affected by bed roughness. The presence of fringing riparian vegetation decreases near-bank flow, increasing the centrifugal force outside of the vegetation but decreasing deposition on the vegetated bar.
Project 3: Appropriate metrics for sediment-related total maximum daily loads
Researchers: Anne Lightbody, Patrick Belmont, Jeff Marr, Cailin Orr, Chris Paola, Kimberly Hill, John Gaffney
The most common cause of impaired rivers and streams in the United States is sediment pollution. High levels of suspended sediment reduce aquatic health both through direct physical mechanisms (interfering with the operation of fish gills and macroinvertebrate feeding, abrading benthic organisms, reducing hyporheic exchange, and smothering fish eggs) and indirectly by reducing light transmission and increasing turbidity. In this project, OSL researchers compared various metrics for determining the effect of sediment pollution. To do so, water with different compositions of suspended load (e.g., different proportions of fine sand, silt, and mud and different levels of organic matter and nutrients), but the same turbidity level was introduced half way down the OSL channel. Researchers then observed the impacts of sediment on physical metrics (embeddedness, permeability), macroinvertebrates, and warm-water fish (smallmouth bass and whitesuckers). Trials were performed under high-flow conditions, typical of storms which exert substantial stress on aquatic ecosystems. Results indicated that suspended sediment affected benthic habitat but that turbidity readings did not fully explain the observed community response. These results will help federal and state agencies to modify their regulations and to better protect the water quality of the nation’s rivers and streams.
Project 4: Residence times and ecological implications of geomorphology-driven subsurface flow
Researchers: Vaughan Voller, Jacques Finlay, Cailin Orr, Jeff Marr, Anne Lightbody, NCED visitors
Rivers and aquifers are three-dimensionally connected at multiple scales, and fluid flux between surface and subsurface zones mediates important naturally occurring biogeochemical and ecological processes. Here, OSL researchers designed, installed, and monitored a high-resolution three-dimensional network of near-stream piezometers to characterize hyporheic water flow and to determine the change and variability in nutrient concentrations. The resulting high-resolution flow-path map revealed that the surface topography increased water flux through the meander bend. Nutrient levels within the subsurface and soil conductivity also changed across the point bar as a result of intense microbial activity. These components will advance the long-term goal of understanding and predicting the feedbacks between surface geomorphology, subsurface residence times, microbial community dynamics, and nutrient processing.
Project 5: Water residence time and sedimentation within patches of aquatic vegetation
Researchers: Anne Lightbody, Chris Paola, NCED visitor program participants
The presence of aquatic vegetation in river channels results in an increase in flow resistance and a reduction in conveyance capacity. However, by enhancing water quality, creating ecologically productive riparian zones, improving in-stream habitat, and stabilizing banks, aquatic vegetation plays a crucial role in river restoration in the United States. This project validated models that predict the residence time and turbulence levels of a patch of aquatic vegetation under field conditions. In particular, OSL researchers found that the size and stem density of aquatic vegetation patches determines turbulence levels within the vegetation, and the lateral and vertical exchange of dissolved solutes and sediment between the vegetation and the free stream. Patch-scale measurements of velocity, turbulence, tracer retention, and sedimentation were compared to simultaneous reach-scale tracer studies to document the effect of vegetation on increasing flow diversity and sediment storage within the reach.
Please contact us about research and educational opportunities at any of the StreamLab facilities. Click here to view the Outdoor StreamLab brochure. |
