Sediment Transport In The Lower Snake And Clearwater River Basins Idaho And Washington 200811 PDF Download

This report and associated web site files provide sediment transport and related data for coarse-bed streams and rivers to potential users. Information on bedload and suspended sediment transport, streamflow, channel geometry, channel bed material, floodplain material, and large particle transport is provided for 33 study reaches in Idaho that represent a wide range of drainage areas, average annual streamflows, channel gradients, and substrate sizes. All the study reaches have a coarser layer of surface bed material overlaying finer subsurface material. Both bedload and suspended sediment transport increase with discharge and the relationship can be reasonably represented using a log-log model. At most sites, the suspended load makes up the majority of the total sediment load. The size of the largest bedload particle in transport and usually the median size of the bedload increase with discharge. However, the median size of the bedload is much smaller than the channel surface material and sand is the primary or a large component of the bedload material. A large proportion of the annual sediment production occurs at the higher streamflows during snowmelt. On average, discharges equal to or larger than bankfull occur 3.3 percent of the time and transport 61.5 percent of the annual bedload sediment. Discharges less than the average annual discharge, on average, occur 75.0 percent of the time and transport about 3.8 percent of the annual bedload sediment.