Abstract
Salmon and steelhead trout populations have declined over the past 100 years on the Lower American River to levels that are so low, sustainability is now questioned. Anthropogenic changes to the Lower American River (LAR) have dramatically altered or removed spawning habitat, reducing the likelihood of species recovery. This thesis examines three restoration projects conducted in the LAR to enhance spawning habitat. The Lower American River is 23 miles of unobstructed channel that flows from Folsom and Nimbus dams to downtown Sacramento and the confluence with the Sacramento River. The majority of salmon and steelhead trout spawning occur in the upper most 4 miles of river from the Nimbus dam downstream to American Bar below Sunrise river access. Restoration work occurred at Sailor Bar and Lower Sunrise in 2008 and 2009. For this restoration work, gravel was added in two locations at Sailor Bar and a side channel was created at Lower Sunrise. Analysis of each restoration project was based on the following objectives: • Characterization of grain size in the restoration areas using Wolman pebble counts and bulk sampling methods. • Installation of mini piezometers to measure water quality at 30 cm depth. Temperature, Dissolved Oxygen, Electrical Conductivity, pH, and Turbidity were measured at each mini piezometer. • Measurement of depth and water velocity at each mini piezometer location • Tracer tests were conducted to evaluate seepage velocity • Tracer rocks were deployed to understand the movement of gravel with varying flow conditions Both gravel additions at Sailor Bar greatly improved the grain size and available oxygen after gravel was added at both Sailor Bar locations. The Sunrise side channel was constructed and flows according to design specifications. The side channel is flowing with channel velocities and depths, grain size, and dissolved oxygen appropriate for spawning salmon and steel head trout.