Supplementary material to “Measuring Bed Load Discharge in Rivers”

John R. Gray, U.S. Geological Survey, Reston, Virginia; Jonathan B. Laronne, Ben Gurion University of the Negev, Beer Sheva, Israel; Jeffrey G. D. Marr, St. Anthony Falls Laboratory, Minneapolis, Minnesota

Citation: Gray, J. R., J. B. Laronne, and J. G. D. Marr (2007), Measuring Bed Load Discharge in Rivers, Eos Trans. AGU, 88(45), 471. [Full Article (pdf)]

SYNOPSIS OF OUTCOMES FROM THE INTERNATIONAL BEDLOAD-SURROGATE MONITORING WORKSHOP, MINNEAPOLIS, MINNESOTA, USA, APRIL 11-14, 2007

John R. Gray¹, Jonathan B. Laronne² and Jeffrey G.D. Marr³

¹U.S. Geological Survey, Reston, Virginia, USA

²Ben Gurion University of the Negev, Beer Sheva, Israel

³St. Anthony Falls Laboratory, Minneapolis, Minnesota, USA

The International Bedload Surrogates Monitoring Workshop¹, organized by the Bedload Research International Cooperative^2,3,4 (BRIC) on April 11-14, 2007, in Minneapolis, Minnesota, USA, was held to:

a. determine the extent to which available bedload-surrogate technologies have progressed to wise usage based on calibration under laboratory and field conditions;

b. further the development and verification of novel bedload-surrogate technologies and methodologies toward their routine application in large-scale monitoring programs; and

c. identify needs related to international standards on bedload data-collection,-storage, and -dissemination protocols. 

About 50 geomorphologists, sedimentologists, hydraulic engineers, hydrologists, and others with expertise and (or) interest in bedload monitoring representing nine countries convened at the St. Anthony Falls Laboratory⁵.  Others from around the world participated via live webstream on April 11-13, which was archived for perpetuity.

Outcomes from the workshop include proceedings to be released by 2008 with at least 25 peer-reviewed papers primarily dealing with issues of calibration of bedload-surrogate technologies and state of the art bedload-surrogate monitoring. It will also include the principal workshop recommendations; identification of compelling bedload-surrogate technologies and related issues in data acquisition; recommendations of methods to bring selected technologies to fruition; and identification of other issues and needs germane to the international bedload-research community.

The workshop was predicated on recognition of the research community’s long-standing inability to resolve a variety of difficulties in measuring and monitoring bedload discharge (transport), particularly in gravel and mixed gravel-sand bedded rivers. Direct bedload measurements, particularly during medium and high flows when most bedload occurs, tend to be time-consuming, expensive, and potentially hazardous. Indirect or surrogate technologies developed largely over the last decade and used at a number of research sites around the world show considerable promise toward providing relatively dense, robust, and quantifiably reliable bedload datasets. However, information on the relative performance, scope of applicability and ultimate efficacy of selected technologies for use in monitoring programs is needed, as is identifying methods for bringing the most promising and tractable of the technologies to fruition.

Three principal recommendations emanated from the workshop:

1. Provide Access to Bedload and Ancillary Data Worldwide:  The desire for access to a broad spectrum of bedload data from around the world was unanimous among workshop participants. Anticipated limitations in resources seem to preclude development, population, and maintenance of a central database. An alternate approach to bedload-data access was described as follows:

a. Form an ad hoc committee to define the objectives and approach toward accessing bedload and ancillary data worldwide. Identify potential partners in this effort, such as the National Center for Earth-surface Dynamics⁷.

b. Locate and post on-line static (historical) bedload and ancillary databases that do not require refreshment and maintenance.

c. Identify and access dynamic databases with bedload and ancillary data worldwide, such as the U.S. Geological Survey’s National Water Information System⁸. Provide metadata on each database, including protocols by which the data were collected and analyzed.

d. Develop sequential query language or other script-type language that can extract data on request from the static and dynamic databases.

e. Enable access or make available information related to access to the suite of bedload and ancillary databases through the Bedload Research International Cooperative home page⁴ free-of-charge.

This concept has been articulated in some detail by Gray and Osterkamp (2007)⁹. Collaborators that have expressed some level of interest include the National Center for Earth-surface Dynamics⁷ and the World Association for Sedimentation and Erosion Research¹⁰.

2. Develop and Implement a BRIC Benchmark Network:  A number of bedload researchers have developed novel techniques for intermittently or continuously monitoring bedload transport. However, some lack the capacity or access to appropriate facilities to compare their techniques to “ground truth.” Ironically, there are a large number of sites – both controlled, such as laboratory flumes equipped with sediment-measuring devices; and uncontrolled, such as Reid-type (formerly termed Birkbeck) slot samplers set in natural channels and operational during runoff – where reliable bedload-transport rates can be derived.

Recognizing this fundamental need and the availability of a number of facilities capable of providing bedload-transport ground truth, the workshop attendees were unanimous in their recommendation for the BRIC to develop a Bedload Benchmark Network. Such a network would consist of sites and facilities that:

a. possess the facilities and capabilities that enable reliable computations of bedload transport;

b. agree to join and collaborate as part of the BRIC Benchmark Network; and

c. is coordinated by a BRIC-organized committee to help researchers in the selection of an appropriate bedload-research venue.

At least 20 such venues have already been identified as potential BRIC Benchmark Network research sites (Gray, et al., in press³).

3. Summarize the Status of Progress in Bedload-Surrogate Technologies:  A primary thrust of the workshop was to compile and evaluate information on bedload-surrogate technologies and to identify those that show the most promise for monitoring bedload as part of operational programs in a quantifiably reliable way. Papers presented at the workshop will be published in a USGS Scientific Investigations Report, on a wide range of technologies, most of which were based on active or passive hydroacoustic techniques. Surrogate technologies based on magnetic and impact sensing are presently less developed for use in the near future. The hydroacoustic technologies are summarized below:

Active Hydroacoustics: This technology focused on stationary deployment of an acoustic Doppler Current Profiler (ADCP) in sand-bed systems. The net downstream movement of near-bed sediments causes a bottom-referenced ADCP to incorrectly infer that the device is moving in the upstream direction. Hence, for ADCP flow measurements, a “moving-bed correction” is required (Mueller and Wagner, 2006¹¹). The “moving-bed correction” is being used to infer bedload transport in conjunction with bedload measurements, such as in a flume with a slot-sampler, or otherwise using a portable bedload sampler.

Passive Hydroacoustics: This technology uses hydrophones or geophones to measure the intensity of natural sounds emitted in gravel-bed channels during runoff. The sound intensity is related to bedload-transport rates, and has been shown to be the case in a field and a flume study. Geophones resting on the bed and consisting of a pipe or impact plate and hydrophones deployed within the water near the bed have been tested. Geophones have been satisfactorily calibrated either in the lab (plates) or also in Nature (pipe).

Links and References

¹www.nced.umn.edu/BRIC_2007.

²Gray, J.R., Laronne, J.B., and Osterkamp, W.R., 2007, Bedload Research International Cooperative: Proceedings of the 10th International Symposium on River Sedimentation, Moscow, Russia, August 1-4, 2007, vol. III, pp. 120-126.

³Gray, J.R., Laronne, J.B., Osterkamp, W.R. and Vericat, D., in press, Bedload Research

International Cooperative—BRIC:  Proceedings of the International Bedload-Surrogate Monitoring Workshop, April 11-14, 2007, Minneapolis, Minnesota, USA, 16 p.

⁴www.bedloadresearch.org.

⁵www.safl.umn.edu.

⁶www.nced.umn.edu/BRIC_Archived_Streams.html.

⁷www.nced.umn.edu/.

⁸waterdata.usgs.gov/nwis.

⁹ Gray, J.R., and Osterkamp, W.R., 2007, Vision for a worldwide fluvial-sediment information network: Proceedings 10th International Symposium on River Sedimentation, Moscow, Russia, August 1-4, 2007, vol. I, pp. 43-54.

¹⁰www.waser.cn/.

¹¹Mueller, D.S., and Wagner, C.R., Application of the loop method for correcting acoustic doppler current profiler discharge measurements biased by sediment transport:  U.S. Geological Survey Scientific-Investigations Report 2006-5079, 18 p. (http://pubs.usgs.gov/sir/2006/5079/).