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Floodflow characteristics of the Sacramento River in the vicinity of Gianella Bridge, Hamilton City, California

Open-File Report 81-328

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Abstract

Floodflow, channel, and geomorphic data were assembled to evaluate the characteristics of flooding of the Sacramento River at the Gianella Bridge on State Highway 32 at Hamilton City, Calif. The bridge, constructed with a large center pier and drawrest structure in 1908, constricts floodflows at the site. Variations in river sinuosity, slope, and alinement between 1946 and 1980, indicate that channel changes are significant during short (2- or 3-year) intervals of time. Over long periods, however, the channel appears to be in equilibrium. The flood plain extends several miles upstream and downstream from the site. Soils on the flood plain are sandy-silt loam, easily eroded by streamflow. Overflow to the flood plain is limited by levees along both banks that are overtopped or bypassed when floods exceed 130,000 cubic feet per second in the main channel. Backwater in the main channel upstream from the bridge is about 0.6 feet for flows exceeding 159,000 cubic feet per seconds, and extends more than 1.9 miles upstream, depending on the magnitude of flooding. The bridge structure occupies about 12 percent of the channel during all flows. The distribution of flow at the bridge is affected by piers for about 13 percent of the channel width. Highest velocities of flow are 13 feet per second. (USGS)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Floodflow characteristics of the Sacramento River in the vicinity of Gianella Bridge, Hamilton City, California
Series title:
Open-File Report
Series number:
81-328
Edition:
-
Year Published:
1981
Language:
ENGLISH
Publisher:
U.S. Geological Survey,
Description:
vi, 39 p., 1 over-size sheet ;28 cm.