Issue 16 (1) 2017 pp. 237-246
Tomáš Galia, Václav Škarpich, Kateřina Gajdošová, Petr Krpec
VARIABILITY OF WOLMAN PEBBLE SAMPLES IN GRAVEL/COBBLE BED STREAMS
Keywords: Wolman sampling, bed sediments, mountain stream, flysch
Wolman  pebble sampling is the most commonly used method to estimate surface bed grain sizes in gravel-bed streams. A few studies documented different results between individual operators or repeated measurements within the same channel-reach obtained by this method. We tested potential differences in pebble sample distributions and related grain-size percentiles (D10, D50 and D90) between two fluvial geomorphologists and two almost inexperienced students in three channel-reaches and one gravel bar. None of sampled locations provided statistically consistent particle-size distributions and related percentiles when comparing measurements of all operators. The samples of experienced fluvial geomorphologists were most consistent for the channel-reaches with assumed widest range of particle sizes; a post-hoc test documented significant differences for the gravel bar and the lower plane bed reach. Medians of particle-size distributions for the gravel bar were equal for three of four operators; the fourth operator probably included also coarser particle population between the channel bed and bar. It implies that 100 sampled particles are most likely sufficient only for D50 estimations and homogenous sediment populations (i.e. well-sorted gravel bars). In any other case, much larger number of particles should be sampled in gravel/cobble bed streams to obtain narrower confidence limits of related grain-size percentiles.
|MLA||Galia, Tomáš, et al. "VARIABILITY OF WOLMAN PEBBLE SAMPLES IN GRAVEL/COBBLE BED STREAMS." Acta Sci.Pol. Form. Cir. 16.1 (2017): 237-246. http://dx.doi.org/10.15576/ASP.FC/2017.16.1.237|
|APA||(2017). . Acta Sci.Pol. Form. Cir. 16 (1), 237-246 http://dx.doi.org/10.15576/ASP.FC/2017.16.1.237|
|ISO 690||GALIA, Tomáš, et al. VARIABILITY OF WOLMAN PEBBLE SAMPLES IN GRAVEL/COBBLE BED STREAMS. Acta Sci.Pol. Form. Cir., 2017, 16.1: 237-246. http://dx.doi.org/10.15576/ASP.FC/2017.16.1.237|