Comparison of Three Pebble Count Protocols (EMAP, PIBO, and SFT) in Two Mountain Gravel‐Bed Streams¹

Abstract

Although the term ``pebble count'' is in widespread use, there is no standardized methodology used for the field application of this procedure. Each pebble count analysis is the product of several methodological choices, any of which are capable of influencing the final result. Because there are virtually countless variations on pebble count protocols, the question of how their results differ when applied to the same study reach is becoming increasingly important. This study compared three pebble count protocols: the reach‐averaged Environmental Monitoring and Assessment Program (EMAP) protocol named after the EMAP developed by the Environmental Protection Agency, the habitat‐unit specific U.S. Forest Service’s PACFISH/INFISH Biological Opinion (PIBO) Effectiveness Monitoring Program protocol, and a data‐intensive method developed by the authors named Sampling Frame and Template (SFT). When applied to the same study reaches, particle‐size distributions varied among the three pebble count protocols because of differences in sample locations within a stream reach and along a transect, in particle selection, and particle‐size determination. The EMAP protocol yielded considerably finer, and the PIBO protocol considerably coarser distributions than the SFT protocol in the pool‐riffle study streams, suggesting that the data cannot be used interchangeably. Approximately half of the difference was due to sampling at different areas within the study reach (i.e., wetted width, riffles, and bankfull width) and at different locations within a transect. The other half was attributed to using different methods for particle selection from the bed, particle‐size determination, and the use of wide, nonstandard size classes. Most of the differences in sampling outcomes could be eliminated by using simple field tools, by collecting a larger sample size, and by systematically sampling the entire bankfull channel and all geomorphic units within the reach.

Scaling relationships between bed load volumes, transport distances, and stream power in steep mountain channels

“…The grain‐size distribution (GSD) of the channel bed surface was determined by grid‐by‐number pebble counts in September 2012 using a variant of the Wolman [] procedure, according to Bunte and Abt [, ] and Bunte et al . [] (Figure ). Bed material subsurface GSDs were determined by sieve analysis of three large volumetric samples taken using a three‐sided plywood shield [ Bunte and Abt , ].…”

Enlargement and evolution of a semi‐alluvial creek in response to urbanization

“…Pebble counts were comprised of a minimum of 200 particles and equally sampled all parts of the bed following Bunte et al (2009) and Harrelson et al (1994). Pebble counts were comprised of a minimum of 200 particles and equally sampled all parts of the bed following Bunte et al (2009) and Harrelson et al (1994).…”

Fine Sediment Deposition at Forest Road Crossings: An Overview and Effective Monitoring Protocol

“…This continued until a minimum of 100 pebbles was counted. The pebble count procedure is widely used to assess surface sediment composition by regulatory agencies and researchers alike (Bevenger and King, 1995;Bunte et al, 2009) Overlying water depth and velocity was measured at each sample location for each technique applied. Flow measurements associated with infiltration bag and gravel bucket locations should be collected when the sampler is installed in the streambed and then again before it is removed.…”