Photographic techniques for characterizing streambed particle sizes

Transactions of the American Fisheries Society
By: , and 



We developed photographic techniques to characterize coarse (>2-mm) and fine (≤2-mm) streambed particle sizes in 12 streams in Anchorage, Alaska. Results were compared with current sampling techniques to assess which provided greater sampling efficiency and accuracy. The streams sampled were wadeable and contained gravel—cobble streambeds. Gradients ranged from about 5% at the upstream sites to about 0.25% at the downstream sites. Mean particle sizes and size-frequency distributions resulting from digitized photographs differed significantly from those resulting from Wolman pebble counts for five sites in the analysis. Wolman counts were biased toward selecting larger particles. Photographic analysis also yielded a greater number of measured particles (mean = 989) than did the Wolman counts (mean = 328). Stream embeddedness ratings assigned from field and photographic observations were significantly different at 5 of the 12 sites, although both types of ratings showed a positive relationship with digitized surface fines. Visual estimates of embeddedness and digitized surface fines may both be useful indicators of benthic conditions, but digitizing surface fines produces quantitative rather than qualitative data. Benefits of the photographic techniques include reduced field time, minimal streambed disturbance, convenience of postfield processing, easy sample archiving, and improved accuracy and replication potential.

Publication type Article
Publication Subtype Journal Article
Title Photographic techniques for characterizing streambed particle sizes
Series title Transactions of the American Fisheries Society
DOI 10.1577/1548-8659(2003)132<0605:PTFCSP>2.0.CO;2
Volume 132
Issue 3
Year Published 2003
Language English
Publisher Taylor & Francis
Contributing office(s) Alaska Science Center
Description 6 p.
First page 605
Last page 610
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