Identifying Indicators and Guides for Sustainability of Pools in Gravel-bed Rivers

Project ID: 4362
Principal Investigator: Sharon Parkinson
Research Topic: Sediment Management and River Restoration
Funded Fiscal Years: 2010, 2011 and 2012
Keywords: None

Research Question

Gravel-bed rivers are an important habitat for salmonids, which are at risk throughout the Northwestern United States and are the focus of extensive environmental legislation and litigation. The pool-riffle morphology in gravel-bed rivers is particularly important because the diversity in physical habitat in these reaches is critical for spawning and other life stages.

A hypothesis to explain the persistence of pools has been that of "velocity reversal." The occurrence of velocity reversals has been controversial for over three decades, but a recent study developed a simple criterion that unifies and explains previous disparate findings regarding the occurrence of velocity reversals (Caamaño, D., P. Goodwin, J.M. Buffington, J.C. Liou, and S. Daley-Laursen, 2009. A unifying criterion for velocity reversal hypothesis in gravel-bed rivers. The Journal of Hydraulic Engineering, American Society of Civil Engineers [ASCE] 135(1). 66-70.) The criterion uses simple measurements that can easily be collected in the field (tape for measuring channel width and survey rod for measuring the thalweg depth). Preliminary results from the Red River Wildlife Management Area monitoring program show that reversal depends critically on the ratio of riffle-to-pool width, residual pool depth (difference between pool and riffle elevations), and on the depth of flow over the riffle.

Verifying these criteria for a broader range of field conditions could develop very useful equations and establish guidelines for designing restoration projects that would supplement effective discharge and hydraulic geometry information to allow rapid assessment of pool habitat vulnerability, particularly under potential changes to annual streamflow characteristics due to climate change. These parameters could also be useful in lieu of, or as a supplement to, a more detailed modeling exercise of restoration alternatives.

Need and Benefit

The Columbia and Snake River Salmon Recovery Office (CSRO) receives Federal monies to improve and restore salmonid habitat impacted by the construction of Federal dams. These mitigation efforts include the design of specific habitat features for various life stages of salmonids in various streams or rivers identified throughout the Northwestern United States.

Criteria and knowledge gained from this project have the potential to provide design guidelines, assess the need for engineered features, and provide a means for determining design success metrics.

As a result, the CSRO supports this proposed research project to establish criteria and guidelines that can be used in the design of sustainable pools in gravel-bed rivers. The results of this investigation have wide-reaching applicability for instream habitat projects in subbasins funded by the CSRO as well as Bureau of Reclamation-wide habitat projects.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Quickly Determining Pools and Riffles Stability in Gravel-Bed Rivers (final, PDF, 996KB)
By Sharon Parkinson
Publication completed on September 30, 2014

This bulletin summarizes the research results and potential application to Reclamation's mission.

Not Reviewed

The following documents were not reviewed. Statements made in these documents are those of the authors. The findings have not been verified.

Field Evaluation of a Pool Sustainability Predictor in Gravel Bed Rivers (interim, PDF, 576KB)
By Sharon Parkinson
Publication completed on July 07, 2011

Velocity reversal in pool-riffle sequences has been postulated as the primary mechanism for sustaining pools in gravel-bed rivers.Recent criteria have been developed to predict the occurrence of velocity reversal for a wide range of data published in the literature, but it is unclear whether velocity reversal will sustain pools under all field conditions and what the exceptions might be. The results of a 12-year geomorphic monitoring program in the SF Clearwater River in Idaho are presented.

Flow Structure and Sustainability of Pools in Gravel-bed Rivers (final, PDF, 1.4MB)
By Sharon Parkinson
Report completed on May 14, 2014

Pool-riffle channel morphology in gravel-bed streams creates a range of micro-habitats that are important for maintaining ecological diversity. This study is motivated by the need to restore sustainable spawning and over-wintering habitat for salmon as a means of mit-
igating for dam construction. The velocity reversal hypothesis (Gilbert, 1914, Keller 1971, 1972) has been used as a potential mechanism for the sustainability of pools.

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Last Updated: 6/22/20