WSPC03417 - Laserfiche WebLink

Home Browse Search

0018i9 The Helley-Smith bedload sampler has a well-established sediment-trapping efficiency. Extensive field calibration (Emmett, 1980) was conducted by comparing the transpon rate as measured with the Helley-Smith bedload sampler to the transpon rate as established by a stream- wide bedload trap. That study indicated a 'near-perfect' sediment trapping efficiency for panicle sizes between 0.5 and 16 mm, the panicle sizes in transpon at the calibration facility and the vast majority, by weight, of panicle sizes presented herein. For the present data, a sediment-trapping efficiency of 100 percent was assumed for all panicle sizes. In association with the field calibration of the Helley-Smith sampler. multiple sampling traverses were conducted (Emmett, 1980). These showed that about 20 cross-sectional sampling locations account for the spatial variation in transport rate, and showed that more than two traverses did not greatly change the estimated mean value of bedload transpon. The sampling procedures employed in the collection of bedload data were based upon the Single Equal Width Increment (SEWI) method (Edwards and Glysson, 1988). Multiple samples at equal width intervals across the channel were collected. There were 20 or more subsamples taken during each of two each traverses of the channel, although in earlier years at the Forest Service sites fewer subsamples were collected during a single traverse of the channel. For Forest Service sites, a criterion was established requiring at least 10 subsamples. Each subsample lasted for 30 or 60 seconds unless high transpon rates forced shorter sampling times. The sampling time was constant across a given traverse. To assure that adequate field, laboratory, and office techniques were used in collection and analysis of bedload data, W.W. Emmett routinely met, and/or otherwise corresponded, with those personnel responsible for assembling the sediment data sets presented herein. During his several decades with the USGS, Emmett pioneered research into bedload samplers and proceduresJor their use and was responsible for many of the guidelines that led to standard techniques in bedload sampling. This collaboration assured consistent application of state-of- the-science guidelines. Suspended sediment was also collected at sites though it was not used in quantifying the claims. Suspended-sediment samplers, developed and distributed by the Federal Interagency Sedimentation Project (FISP), are standard in design and use throughout the United States (Edwards and Glysson, 1988; Williams et al., 1988). For use in collecting the suspended- sediment data presented herein, the wading version of the depth integrating sampler is the USDA-48 or USDA-8I, the suspension version of the depth integrating sampler is the USD-74, and the suspension point sampler, albeit used sparingly, is the USP-61. For suspended load, about 10 cross-channel locations are adequate; generally, every other bedload-sampling location sufficed as the cross-channel locations for suspended-load sampling. The vertical transit rate of lowering and raising the suspended-sediment sampler was everywhere an Equal Transit Rate (ETR) to maintain the equal-discharge weighting. Sampling procedures for suspended sediment are quite standard and are well documented (e.g., Edwards and Glysson, 1988; Williams et al., 1988). United States' Expert Report Disclosing Methodologies for Quantification of Organic Act Claims Consolidated Subcase No. 63-25243 29