Field Measurements of Streambed Scour at Bridge Piers in Ohio

Jackson, K. Scott; ,

Field Measurements of Streambed Scour at Bridge Piers in Ohio

by K. Scott Jackson, (M.ASCE),

Document Type: Proceeding Paper

Part of: North American Water and Environment Congress & Destructive Water

Abstract:

Field measurements made from 1989 to 1994 were evaluated to characterize pier scour at 21 bridge sites in Ohio. Pier scour was observed at sites in 45 of 47 real-time scour measurements. The estimated recurrence interval for 27 of 35 corresponding stream-flow measurements on unregulated streams is less than 2 years. Selected observed pier-scour relations are compared to results of previous scour research. Observed pier-scour depths and flow depths ranged from 0.2 to 1.9 m, and 0.9 to 6.0 m, respectively. All pier-scour depths were less than 2.4 times the corresponding pier width. Selected variables were normalized by dividing them by the effective pier width. Normalized scour depth tended to increase with normalized flow depth; the rate of increase in normalized scour depth with increasing normalized flow depth appeared to lessen at normalized flow depths at or above 2.5. Normalized scour depth was found to increase with the median grain size of bed material up to about 10 mm, then decrease for median grain sizes greater than 10 mm. Normalized scour depth was found to decrease as sediment gradation increased. The field measurements tend to support conclusions by previous researchers of streambed scour, except that normalized scour depth has been shown to decrease consistently with increasing median grain size.

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