Columbia River Suspended Sediment Monitoring

For the past two springs we have monitored suspended particulate matter (SPM) in the tidal-fluvial part of the Columbia River, 86 km from the mouth. We have monitored SPM with a LISST-floc, which measures sediment volume concentration in 32 log spaces particle size bins from 8 to 1500 microns. Periodic site visits have included filter sampling to determine mass concentration and an estimate of representative fall velocity. A USGS station also located at the Beaver site supports an ADP (velocity and acoustic backscatter), water level gage, and turbidimeters. Comparison of LISST and turbidimeter gages illustrates the importance of grain size data information in sediment monitoring. In both 2003 and 2004 we captured minor winter high flow events. Both years also captured data from spring freshets resulting from melting of snows in the Columbia River Interior Sub-basin. However, 2003 included heavier spring rains whereas 2004 included ligher spring rains. In June 2004 the LISST-floc was deployed in cast mode in the Columbia River estuary allowing comparison of suspended sediment in the freshwater river with suspended sediment in the saline estuary. The complex sediment processes in the estuary noticeably alter riverine sediment input.