Observed and Predicted Pier Scour in Maine

Water-Resources Investigations Report 2002-4229
Prepared in cooperation with the Maine Department of Transportation
By:  and 



Pier-scour and related data were collected and analyzed for nine high river flows at eight bridges across Maine from 1997 through 2001. Six bridges had multiple piers. Fifteen of 23 piers where data were measured during a high flow had observed maximum scour depths ranging from 0.5 feet (ft) to 12.0 ft. No pier scour was observed at the remaining eight piers. The maximum predicted pier-scour depths associated with the 23 piers were computed using the equations in the Federal Highway Administration's Hydraulic Engineering Circular number 18 (HEC-18), with data collected for this study. The predicted HEC-18 maximum pier-scour depths were compared to the observed maximum pier-scour depths. The HEC-18 pier-scour equations are intended to be envelope equations, ideally never underpredicting scour depths and not appreciably overpredicting them. The HEC-18 pier-scour equations performed well for rivers in Maine. Twenty-two out of 23 pier-scour depths were overpredicted by 0.7 ft to 18.3 ft. One pier-scour depth was underpredicted by 4.5 ft. For one pier at each of two bridges, large amounts of debris lodged on the piers after high-flow measurements were made at those sites. The scour associated with the debris increased the maximum pier-scour depths by about 5 ft in each case.

Study Area

Publication type Report
Publication Subtype USGS Numbered Series
Title Observed and Predicted Pier Scour in Maine
Series title Water-Resources Investigations Report
Series number 2002-4229
DOI 10.3133/wri20024229
Edition -
Year Published 2002
Language ENGLISH
Publisher Geological Survey (U.S.)
Contributing office(s) Maine Water Science Center
Description iv, 22 p.
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