Heather M Bragg

Executive SummaryChapter A. IntroductionFall Creek Dam impounds Fall Creek Lake, a 10-kilometer-long reservoir in western Oregon and is operated by the U.S. Army Corps of Engineers (USACE) primarily for flood-risk management (or flood control) in late autumn through early spring months, as well as for water quality, irrigation, recreation, and habitat in late spring through early autumn...

Sediment transport, turbidity, and dissolved oxygen were evaluated during six consecutive water years (2013–2018) of drawdowns of a flood control reservoir in the upper Willamette Valley, Oregon, USA. The drawdowns were conducted to allow volitional passage of endangered juvenile chinook salmon through the dam's regulating outlets by lowering the reservoir elevation to a point where the...

Annual reservoir drawdowns at Fall Creek Lake, Oregon, have occurred for eight consecutive years from December 2012 to November 2019. The annual drawdowns are the result of the 2008 Biological Opinion of the US Army Corps of Engineers (USACE) Willamette Valley Project operations, which directed the USACE to carry out interim operational measures that would provide volitional downstream...

Significant Findings An analysis of total-dissolved-gas (TDG) and water-temperature data collected at eight fixed monitoring stations on the lower Columbia River in Oregon and Washington in water year 2015 indicated the following: All but 1 of the 85 TDG sensor laboratory checks that were performed after field deployment were within ±0.5-percent saturation of a primary standard. After 3...

In October 2011, the U.S. Geological Survey began investigating and monitoring water-quality conditions and suspended-sediment transport in the Wilson and Trask Rivers, northwestern Oregon. Water temperature, specific conductance, turbidity, and dissolved oxygen were measured every 15–30 minutes in both streams using real-time instream water-quality monitors. In conjunction with the...

Significant Findings An analysis of total-dissolved-gas (TDG) and water-temperature data collected at eight fixed monitoring stations on the lower Columbia River in Oregon and Washington in water year 2014 indicated the following: All 81 TDG sensor laboratory checks that were performed after field deployment were within plus or minus (±) 0.5-percent saturation of a primary standard...

Significant Findings An analysis of total-dissolved-gas (TDG) and water-temperature data collected at eight fixed monitoring stations on the lower Columbia River in Oregon and Washington in water year 2013 indicated the following: During the spill season of April–August 2013, the averages of the 12 highest hourly TDG values in a day were periodically greater than 115-percent saturation...

The drawdown of Fall Creek Lake resulted in the net transport of approximately 50,300 tons of sediment from the lake during a 6-day drawdown operation, based on computed daily values of suspended-sediment load downstream of Fall Creek Dam and the two main tributaries to Fall Creek Lake. A suspended-sediment budget calculated for 72 days of the study period indicates that as a result of...

Significant Findings Air is entrained in water as it is flows through the spillways of dams, which causes an increase in the concentration of total dissolved gas in the water downstream from the dams. The elevated concentrations of total dissolved gas can adversely affect fish and other freshwater aquatic life. An analysis of total-dissolved-gas and water-temperature data collected at...

Significant Findings An analysis of suspended-sediment transport in the Johnson Creek basin, Oregon, during water years 2007–10 indicated that: Streamflow characteristics for the 4 years of study were not extremely dry or wet, and represented near-average conditions. Computed average annual suspended-sediment loads were 1,890 and 4,640 tons at the Gresham and Milwaukie stations...

The October 2007 breaching of a temporary cofferdam constructed during removal of the 15-meter (m)-tall Marmot Dam on the Sandy River, Oregon, triggered a rapid sequence of fluvial responses as ~730,000 cubic meters (m3) of sand and gravel filling the former reservoir became available to a high-gradient river. Using direct measurements of sediment transport, photogrammetry, airborne...

Significant Findings Air is entrained in water as it is flows through the spillways of dams, which causes an increase in the concentration of total dissolved gas in the water downstream from the dams. The elevated concentrations of total dissolved gas can adversely affect fish and other freshwater aquatic life. An analysis of total-dissolved-gas and water-temperature data collected at...