3) Streambed particle data

Seventeen streamflow-gaging stations, operated by the U.S. Geological Survey and distributed across the Ouachita Mountains of Arkansas and Oklahoma were selected for analysis. Bed material sampling was conducted to obtain information on the particle-size distributions of the streambed materials and to determine the shapes of the individual particles comprising the streambeds. Information on stream-bed particle-size distribution was used to compute the potential rate of bed-load transport and is a parameter used in the Rosgen (Rosgen, 1996) stream reach classification system. Streambed-material particle sizes were measured using two methods. The first method was Wolman pebble counts conducted across the riffles and pools within each study reach. A step-toe procedure was used to collect approximately 100 samples at each riffle and pool. Materials only from the active streambed were measured. For each sample the longest (A) axis, intermediate (B) axis, and shortest (C) axis were measured and recorded. From this pebble count data the bedrock tallies were removed and cumulative frequency curves were developed, from which the median (D50) and one standard deviation from the median (D16 and D84) particle sizes were determined. Bedrock is defined as any exposure of native solid rock in the streambed or along the streambanks. The second streambed-material particle-size sampling method was a sieve analysis of bar samples. A 5-gallon pail (approximately 50 – 60 lbs) of bar gravel was collected from the downstream face of a point-bar approximately 1/3 of the way down the face. The sample was dried and weighed to the nearest 0.1 of a gram to determine the total sample weight. The sample was then placed in a nest of sieves and a mechanical sieve shaker was used to shake the sample particles through the sieves. Next, the particles from each sieve were removed and weighed. The final total weights retained on each sieve were summed and compared to the original total weight before sieving. From the weight retained on each sieve cumulative frequency curves were developed, the median (D50) and one standard deviation from the median (D16 and D84) particles sizes were determined. References Rosgen, D.L., 1996, Applied river morphology: Pagosa Springs, Colorado, Wildland Hydrology Books, 390 p. This child item contains particle information for the 17 study sites. The data for each site is in a zipped file including: 1) Tables with study site Wolman pebble and bar measurements (CSV files). 2) Graphs of streambed particle size cumulative frequency curves and particle shape analysis (JPG files).