Hydrogeomorphic effects of controlled floods on native versus non-native seedlings
On the Bill Williams River (BWR), AZ, we have documented the geomorphic and vegetation responses to a series of controlled flood releases from a U.S. Army Corps dam. These floods, although small compared to historic floods on the BWR, were designed with input from scientists in order to investigate the hydrograph characteristics needed to promote establishment of native riparian vegetation (primarily cottonwood and willow), to cause mortality of non-native tamarisk seedlings, and to affect geomorphic changes associated with vegetation responses. The BWR is serving as a unique natural laboratory for investigating ecosystem responses to flow regimes and thereby for improving the quantitative basis of environmental flows. Environmental flow releases on the BWR are motivated by the presence of a high-quality native riparian ecosystem and associated bird communities, and are part of a broader partnership between The Nature Conservancy and Army Corps of Engineers, the Sustainable Rivers Project.

We are also using flow and sediment transport modeling with the USGS Multidimensional Surface Water Modeling System (MDSWMS) to assess relationships between hydrograph characteristics, channel morphology, hydraulics, and vegetation response.

Milltown Dam, Clark Fork River, MT
Milltown Dam, located on the Clark Fork River just east of Missoula, is being removed in stages between 2007 and 2009. Contaminated sediments originating from mines near Butte, MT are being removed from Milltown Reservoir, but a substantial volume of less contaminated sediments will be available for downstream transport into the Clark Fork River. I plan on investing substantial research energy in the coming years towards documenting evolution of channel morphology and aquatic habitat in the Middle Clark Fork River following removal of Milltown Dam.

Learn more about issues associated with Milltown Dam:
Clark Fork River Technical Assistance Committee

Fossil Creek Diversion Dam, AZ
In collaboration with Leonard Sklar (SFSU), Jane Marks (NAU) and other researchers at NAU, I will also be investigating removal of Fossil Creek Diversion Dam on Fossil Creek, AZ. Fossil Creek is a remarkable stream in which calcium carbonate precipitates out of carbonate-rich water to form travertine dams. Following a decommissioning agreement with Arizona Public Service, full flows were returned to Fossil Creek in 2005. The next phase of the project decommissioning will entail removal of Fossil Creek Diversion Dam in 2008-09. We have been studying geomorphic-ecosystem interactions in response to flow restoration, and we will complement these studies with investigations of dam removal and downstream transport of reservoir sediments. This work will offer fundamental insights into sediment routing through a steep, step-pool and bedrock system, ecogeomorphic responses to sediment pulses, and effective discharges in spring-dominated systems.

Learn more about the restoration of Fossil Creek and associated research:
Fossil Creek Watershed and Riparian Restoration Project

Steep channel processes
I also study flow hydraulics and morphology of step-pool stream channels, which are high-gradient channels in which channel-spanning steps formed by boulders, woody debris, or bedrock alternate with pools. My work seeks to increase understanding of basic physical processes in these channels and to elucidate how these channels differ from low-gradient stream channels. Such knowledge is critical for analyses of sediment transport, aquatic habitat, stream restoration, and other resource management issues in low-order mountain watersheds.

Flow resistance dynamics in step-pool channels
My doctoral research examined flow resistance dynamics in step-pool channels. Using a laboratory flume configured to resemble a step-pool channel, I investigated several questions: (1) What are the dominant controls on flow resistance in step-pool channels, (2) How does large woody debris (LWD) influence hydraulics in step-pool channels, and (3) How is flow resistance partitioned among LWD, steps, and grains? Approximately 400 flume runs were completed using a factorial experimental design in which variables contributing to flow resistance in step-pool channels were manipulated, including LWD configurations (density, orientation, piece length, arrangement), step geometry, discharge, bed slope, and presence versus absence of steps and grains. The experiments employed a 10-m long, 0.6-m wide recirculating flume at Colorado State University's Engineering Research Center. (pdf1, pdf2)

Velocity and turbulence characteristics in step-pool channels
My research also investigates spatial and temporal variations in velocity and turbulence characteristics in step-pool channels in order to provide insight into patterns of energy dissipation and flow structure in these channels. This has entailed detailed field measurements of three-dimensional time-averaged and turbulent velocity components using a SonTek FlowTracker Acoustic Doppler Velocimeter (ADV). Primary field sites have included East St. Louis Creek, Colorado, and the Rio Cordon, Italy, which differ in terms of climate, sediment supply, and land use. Collaborators on this work include Ellen Wohl (Colorado State) and Francesco Comiti (University of Padua, Italy). (pdf)

Other previous work on steep channels:
—Linkages between hydraulics, morphology, and benthic communities in high-gradient streams
—Downstream hydraulic geometry of mountain streams (pdf)

Office: Charles H. Clapp Building 355
Phone: 406-243-4761
Fax: 406-243-4028
andrew.wilcox[at]umontana.edu