Significant Findings

An analysis of sediment transport in the North Santiam River basin during water years 2005–08 indicated that:

• Two-thirds of sediment input to Detroit Lake originated in the upper North Santiam River subbasin.
• Two-thirds of the sediment transported past Geren Island originated in the Little North Santiam River subbasin.
• The highest annual suspended-sediment load at any of the monitoring stations was the result of a debris flow on November 6, 2006, on Mount Jefferson.
• About 86 percent of the total sediment input to Detroit Lake was trapped in the lake, whereas 14 percent was transported farther downstream.
• More than 80 percent of the sediment transport in the basin was in November, December, and January.
• The variance in the annual suspended-sediment loads was better explained by the magnitude of the annual peak streamflow than by the annual mean streamflow.