By Kristin Bunte & Kurt W. Swingle

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ISBN (electronic): 978-90-836443-5-6

ISBN (printed): 978-90-836443-4-9 

ISSN: 2959-7978

DOI: 10.64697/iahr.watermonograph.007

 About the IAHR Water Monograph

Large differences have been reported for gravel bedload transport rates and their associated particle sizes measured with different samplers, both in flume and field studies. However, the differences vary widely between studies, and little is known about the processes or mechanisms causing those differences.

This monograph compares gravel bedload measurements made with the commonly used 76 by 76 mm opening Helley-Smith pressure-difference sampler (H-S) to those made with bedload traps during snowmelt seasons at 19 sites in Rocky Mountain streams. Bedload traps are samplers specifically designed for collecting accurate samples of gravel bedload in coarse-bedded wadeable streams. Their unflared openings are 0.3 m wide, and bedload is collected in a 1.2 m long attached bag (4 mm mesh width). Bedload traps are deployed on ground plates anchored in the bed and spaced by 1-1.5 m across the stream, and sampling duration is typically an hour.

 About the Authors

Kristin Bunte is a retired research scientist from Colorado State University (USA). Most of her work on mountain gravel-bed streams was funded by the USDA Forest Service and focused on practical applications for field practitioners. She obtained her Ph.D. from the Free University of Berlin (Germany) studying gravel transport in a Montana mountain stream and later conducted postdoctoral research in Belgium and at Colorado State University. 

Kurt Swingle is an environmental scientist with an MS in biology.  He has worked as a consultant on various Superfund clean-up projects including the Rocky Mountain Arsenal and the Nevada Nuclear Test Site. For the past 22 years he worked with Kristin Bunte on small stream sediment transport in Colorado, Wyoming, and, most recently, Japan. He was involved in the development and use of bedload traps and collected much of the Helly Smith samples described in this report. 

 Opinions from experts

This IAHR Water Monograph is probably the best documented on bedload samplers and their limitations. The work is outstanding and compiles the results of over 20 years of field investigation. It is priceless for those wishing to sample bedload in the future, and this document will undoubtedly become a reference.

Alain Recking

Authors present a detailed and methodologically robust comparison of gravel bedload measurements using Helley-Smith and bedload trap samplers in mountain streams. Considering the wide (and often unquestioned) deployment of the H-S technique in diverse field conditions, a rigorous assessment of its accuracy compared to the bedload trap technique is of particular interest.

Kamal El Kadi Abderrezzak

 How to cite

Bunte, K & Swingle, K. (2026). Gravel-Transport Measurements: Different Samplers Different Results. IAHR Water Monograph Series. International Association for Hydro-Environment Engineering and Research. 

 IAHR Water Monographs Series

The IAHR Water Monograph Series highlightscutting-edge advancements in water science andengineering as part of IAHR's commitment to future-oriented initiatives.

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