Laserfiche WebLink
<br />001817 <br /> <br />B. Sediment Data and Analysis <br /> <br />1. Sediment Data <br /> <br />Sediment transpon data was used to develop relationships with streamflow. These <br />relationships and the long term record of streamflow were used to determine average annual <br />sediment production and sediment production for any desired range of stream discharge. The <br />understanding of the cumulative amount of sediment production in relationship to the range and <br />frequency of streamflows was an integral pan of developing the channel maintenance claims. <br /> <br />Sediment transpon data collected at the channel maintenance claim and fluvial process <br />study sites included measurements of both bedload and suspended load. At those claim sites <br />associated with USGS gaging stations and Johnson Creek, the USGS was contracted in 1994 and <br />1995 to visit each site approximately 15 times each year during the spring snowmelt to measure <br />sediment transpon. The USGS made additional measurements during a winter flood of water <br />year 1996 on the Selway River, the Lochsa River and the North Fork Clearwater River and <br />during the spring snowmelt period on the Boise River. Data were also available for water years <br />prior to 1994 from one USGS site associated with a channel maintenance claim, South Fork <br />Salmon River, water years 1985 and 1986 (Williams et al., 1989) and one USGS site associated <br />with a fluvial process study site, Little Granite Creek, water years 1982-93. At claim sites <br />associated with Forest Service gaging stations, sediment transpon data of good quality usually <br />existed dating from 1986. For each of these sites, there are over 100 values of bedload transpon. <br />At other Forest Service gages elsewhere in Idaho, sediment has been collected for a variety of <br />purposes. Personnel from Case Western Reserve University (CWRU) measured sediment <br />transpon during the spring snowmelt periods of 1994 and 1995 at the following fluvial process <br />study sites: Marsh Creek, Fourth of July Creek, Herd Creek, Thompson Creek, and Squaw Creek <br />(USGS). CWRU personnel also measured sediment transport at Valley Creek. Sediment <br />transport measurements have continued at many of the USGS and Forest Service sites in water <br />years 1996 and 1997 (data not available yet). <br /> <br />2. Sampling Equipment and Procedures <br /> <br />Although several types of bedload samplers are in use world-wide, the Helley-Smith <br />bedload sampler is the most commonly used sampler and was used at all sites (Figure 4). The <br />Helley-Smith bedload sampler (Helley and Smith, 1971) is a pressure-difference sampler with an <br />expanding nozzle attached to a 0.25 mm mesh sample bag. The nozzle may be rod mounted for <br />measurement while wading or frame mounted for measurement while suspended from a <br />cableway, bridge or boat. The standard nozzle has a 3-in (76.2 mm) square entrance, but a <br />twice-scale model has a 6-in (152 mm) square entrance. Frames have various weights for <br />various flow conditions, and nozzle size is selected to be adequate for panicle sizes in transport. <br /> <br />United Slates' Expe~ Report DOcIosing Melhodologies for Quantification of Organic Act Claims Consolidated Subcase No, 63-25243 <br /> <br />27 <br />