Geology topics

Jeffrey D. G. Marr

Publications and source records attributed to Jeffrey D. G. Marr.

4 recordsLinked to original sources

USGS2010

Bedload-surrogate monitoring technologies

Advances in technologies for quantifying bedload fluxes and in some cases bedload size distributions in rivers show promise toward supplanting traditional physical samplers and sampling methods predicated on the collection and analysis of physical bedload samples. Four workshops held from 2002 to 2007 directly or peripherally addressed bedload-surrogate technologies, and results from these workshops have been compiled to evaluate the state-of-the-art in bedload monitoring. Papers from the 2007 workshop are published for the first time with this report. Selected research and publications since the 2007 workshop also are presented. Traditional samplers used for some or all of the last eight decades include box or basket samplers, pan or tray samplers, pressure-difference samplers, and trough or pit samplers. Although still useful, the future niche of these devices may be as a means for calibrating bedload-surrogate technologies operating with active- and passive-type sensors, in many cases continuously and automatically at a river site. Active sensors include acoustic Doppler current profilers (ADCPs), sonar, radar, and smart sensors. Passive sensors include geophones (pipes or plates) in direct contact with the streambed, hydrophones deployed in the water column, impact columns, and magnetic detection. The ADCP for sand and geophones for gravel are currently the most developed techniques, several of which have been calibrated under both laboratory and field conditions. Although none of the bedload-surrogate technologies described herein are broadly accepted for use in large-scale monitoring programs, several are under evaluation. The benefits of verifying and operationally deploying selected bedload-surrogate monitoring technologies could be considerable, providing for more frequent and consistent, less expensive, and arguably more accurate bedload data obtained with reduced personal risk for use in managing the world's sedimentary resources. Twenty-six papers are published for the first time as part of the 2007 International Bedload-Surrogate Monitoring Workshop (listed in table 2 in alphabetical order by name of first author). Sequential page numbering of the papers begins on page 38, after the last page of the report. The report plus the 26 papers comprise 430 pages.

Scientific Investigations Report↗

USGS2010

Large-scale laboratory testing of bedload-monitoring technologies: Overview of the StreamLab06 Experiments

A 3-month-long, large-scale flume experiment involving research and testing of selected conventional and surrogate bedload-monitoring technologies was conducted in the Main Channel at the St. Anthony Falls Laboratory under the auspices of the National Center for Earth-surface Dynamics. These experiments, dubbed StreamLab06, involved 25 researchers and volunteers from academia, government, and the private sector. The research channel was equipped with a sediment-recirculation system and a sediment-flux monitoring system that allowed continuous measurement of sediment flux in the flume and provided a data set by which samplers were evaluated. Selected bedload-measurement technologies were tested under a range of flow and sediment-transport conditions. The experiment was conducted in two phases. The bed material in phase I was well-sorted siliceous sand (0.6-1.8 mm median diameter). A gravel mixture (1-32 mm median diameter) composed the bed material in phase II. Four conventional bedload samplers – a standard Helley-Smith, Elwha, BLH-84, and Toutle River II (TR-2) sampler – were manually deployed as part of both experiment phases. Bedload traps were deployed in study Phase II. Two surrogate bedload samplers – stationarymounted down-looking 600 kHz and 1200 kHz acoustic Doppler current profilers – were deployed in experiment phase II. This paper presents an overview of the experiment including the specific data-collection technologies used and the ambient hydraulic, sediment-transport and environmental conditions measured as part of the experiment. All data collected as part of the StreamLab06 experiments are, or will be available to the research community.

Book chapter↗

USGS2008

Experimental and field observations of breach dynamics accompanying erosion of Marmot Cofferdam, Sandy River, Oregon

A key issue faced in dam removal is the rate and timing of remobilization and discharge of stored reservoir sediments following the removal. Different removal strategies can result in different trajectories of upstream sediment transport and knickpoint migration. We examine this issue of for the Marmot Dam removal in Sandy River, Oregon, USA using both physical experiments and field studies accompanying removal of the dam in October 2007. The physical experiment was designed to provide insights on how and if the position of a cofferdam notch will affect how reservoir sediments are remobilized, with the goal of minimizing the volume of sediment stranded in terraces. Data and observations indicate that at lower failure discharges, notch position impacts the location of cofferdam failure as well as the location of the first major knickpoint and its trajectory. In particular, notch positions that force the river to migrate laterally in order to adjust to natural valley orientation and morphology were most effective in removing larger volumes of sediment and reducing terrace heights. Actual cofferdam notching to maximize erosion produced extremely rapid and significant erosion of reservoir sediments. Comparison of model results with field observations suggests that the physical experiments provided solid predictions of rates of erosion and overall knickpoint trajectory.

Conference Paper↗

USGS2007

Measuring bed load discharge in rivers: Bedload-surrogate monitoring workshop Minneapolis, Minnesota, 11-14 April 2007

The International Bedload-Surrogate Monitoring Workshop (http://www.nced.umn.edu/BRIC_2007.html), organized by the Bedload Research International Cooperative (BRIC; www.bedloadresearch.org), was held to assess and abet progress in continuous, semiautomated, or fully automated (surrogate) technologies for monitoring bed load discharge in gravel-, sand-, and mixed gravel-sand-bedded rivers. Direct bed load measurements, particularly at medium and high flows, during which most bed load occurs, tend to be time-consuming, expensive, and potentially hazardous. Surrogate technologies developed largely over the past decade and used at a number of research sites around the world show considerable promise toward providing relatively dense, robust, and quantifiably reliable bed load data sets. However, information on the efficacy of selected technologies for use in monitoring programs is needed, as is identification of the ways and means for bringing the most promising and practical of the technologies to fruition.

Eos, Transactions, American Geophysical Union↗