Measurement of Bridge Scour at the SR-32 Crossing of the Sacramento River at Hamilton City, California, 1987-92

Blodgett, J. C.; Harris, Carroll D.; ,

Measurement of Bridge Scour at the SR-32 Crossing of the Sacramento River at Hamilton City, California, 1987-92

by J. C. Blodgett, U.S. Geological Survey, Sacramento, United States,
Carroll D. Harris, U.S. Geological Survey, Sacramento, United States,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering

Abstract:

A study of the State Route 32 crossing of the Sacramento River near Hamilton City, California, is being made to determine those channel and bridge factors that contribute to scour at the site. Three types of scour data have been measured-channel bed (natural) scour, constriction (general) scour, and local (bridge-pier induced) scour. During the years 1979-93, a maximum of 3.4 ft of channel bed scour, with a mean of 1.4 ft, has been measured. Constriction scour, which may include channel bed scour, has been measured at the site nine times during the years 1987-92. The calculated amount of constriction scour ranged from 0.2 to 3.0 ft, assuming the reference is the mean bed elevation. Local scour was measured four times at the site in 1991 and 1992 and ranged from -2.1 (fill) to 11.6 ft , with the calculated amounts dependent on the bed reference elevation and method of computation used. Surveys of the channel bed near the bridge piers indicate the horizontal location of lowest bed elevation (maximum depth of scour) may vary at least 17 ft between different surveys at the same pier and most frequently is located downstream from the upstream face of the pier.

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