Fine sediment infiltration in Chinook spawning gravels in the Sauk River Basin, Washington

Science Center Objects

The Issue: Salmonid fisheries are an important cultural and economic activity and efforts to support a thriving fisheries industry remain a major priority for the Quileute Tribe. Land use changes can have a profound influence on basin sediment production with direct effects on fisheries. A reconnaissance evaluation for water year 1978 indicated that annual sediment loads in the Lower Bogachiel River were approximately 400,000 tons with 120,000 tons delivered by the Calawah River. Additional studies are needed to improve estimates of the seasonal and interannual variability of sediment loads in mountain rivers, including the Upper Bogachiel River and the Calawah River. 

How USGS will help: An understanding of contemporary suspended-sediment loads will inform Tribe management decisions related to prioritizing salmon habitat restoration projects and land use activities and are an important baseline to evaluate climate change shifts in hydrologic and sediment production regimes.

Sauk River

Sauk River

(Credit: Scott Anderson, USGS. Public domain.)

Problem: Salmonid fisheries are an important cultural and economic activity and efforts to support a thriving fisheries industry remain a major priority for the Quileute Tribe. Land use changes can have a profound influence on basin sediment production with direct effects on fisheries. Further, projected climate change will shift hydrologic and sediment production regimes that will affect timing and magnitude of sediment delivery downstream with associated implications on fisheries habitat and productivity. The Upper Bogachiel and Calawah Rivers are adjacent forested mountain watersheds that differ in geological setting and historical and current land use activities. A reconnaissance evaluation for water year 1978 indicated that annual sediment loads in the Lower Bogachiel River were approximately 400,000 tons with 120,000 tons delivered by the Calawah River. Additional studies are needed to improve estimates of the seasonal and interannual variability of sediment loads in mountain rivers, including the Upper Bogachiel River and the Calawah River. These data will inform Tribe management decisions related to prioritizing salmon habitat restoration projects and land use activities and are an important baseline to evaluate climate change shifts in hydrologic and sediment production regimes.

Objectives: The overall objective of the study is to characterize the suspended-sediment load in the Calawah and Upper Bogachiel Rivers, two adjacent rivers with different geologic setting and land use histories to determine the relative importance of sediment/turbidity sources in these rivers and the Quillayute River downstream.

Relevance and Benefits: The study is consistent with the USGS strategic science directions “A National hazards, risk, and resilience assessment program” and “Understanding Ecosystems and Predicting Ecosystem Change” identified in the 2007-17 science strategy of the USGS (U.S. Geological Survey, 2007). The results from this study will help guide future management decisions in the basin by identifying the relative contribution of sediment/turbidity from tributary rivers, and using that information to 1) prioritize protection and/or restoration activities and 2) guide land use management decisions that promote salmonid fisheries production. Further, these data will contribute to on-going USGS research in sediment transport in large alluvial rivers in Washington State, which has focused on rivers draining to Puget Sound and have generally not included rivers draining to the Pacific Coast.

Approach: The study will use surrogate sediment-monitoring technologies to quantify and characterize suspended-sediment on the Calawah and Upper Bogachiel rivers. Specifically, the study includes continuous (15-minute) turbidity and discrete field suspended-sediment concentration (SSC) sampling at an established USGS streamflow gage on the Calawah River (12043000) and a re-established USGS streamflow gage on the Upper Bogachiel River at HWY 101 (12042800). USGS will use the SSC-turbidity relations, the continuous turbidity records, and stream discharge records to estimate suspended-sediment loads for WY 2019 and 2020. Tribal staff trained to assist USGS personnel in suspended-sediment data collection will provide support throughout the duration of the study.