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Development and evaluation of clear-water pier and contraction scour envelope curves in the Coastal Plain and Piedmont Provinces of South Carolina

Scientific Investigations Report 2005-5289

Prepared in cooperation with the South Carolina Department of Transportaton
By:
and
DOI:10.3133/sir20055289

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Abstract

The U.S. Geological Survey in cooperation with the South Carolina Department of Transportation collected clear-water pier- and contraction-scour data at 116 bridges in the Coastal Plain and Piedmont Physiographic Provinces of South Carolina. Pier-scour depths collected in both provinces ranged from 0 to 8.0 feet. Contraction-scour depths collected in the Coastal Plain ranged from 0 to 3.9 feet. Using hydraulic data estimated with a one-dimensional flow model, predicted clear-water scour depths were computed with scour equations from the Federal Highway Administration Hydraulic Engineering Circular 18 and compared with measured scour. This comparison indicated that predicted clear-water scour depths, in general, exceeded measured scour depths and at times were excessive. Predicted clear-water contraction scour, however, was underpredicted approximately 30 percent of the time by as much as 7.1 feet.

The investigation focused on clear-water pier scour, comparing trends in the laboratory and field data. This comparison indicated that the range of dimensionless variables (relative depth, flow intensity, relative grain size) used in laboratory investigations of pier scour, were similar to the range for field data in South Carolina, further indicating that laboratory relations may have some applicability to field conditions in South Carolina. Variables determined to be important in developing pier scour in laboratory studies were investigated to understand their influence on the South Carolina field data, and many of these variables appeared to be insignificant under field conditions in South Carolina. The strongest explanatory variables were pier width and approach velocity. Envelope curves developed from the field data are useful tools for evaluating reasonable ranges of clear-water pier and contraction scour in South Carolina. A modified version of the Hydraulic Engineering Circular 18 pier-scour equation also was developed as a tool for evaluating clearwater pier scour. The envelope curves and modified equation offer an improvement over the current methods for predicting clear-water scour in South Carolina.

Data from this study were compiled into a database that includes photographs, measured scour depths, predicted scour depths, limited basin characteristics, limited soil data, and modeled hydraulic data. The South Carolina database can be used to compare studied sites with unstudied sites to evaluate the potential for scour at the unstudied sites. In addition, the database can be used to evaluate the performance of various methods for predicting clear-water pier and contraction scour.

Suggested Citation

Benedict, S.T., and Caldwell, A.W., 2016. Development and evaluation of clear-water pier and contraction scour envelope curves in the Coastal Plain and Piedmont Provinces of South Carolina (ver. 1.1, August 2016): U.S. Geological Survey Scientific Investigations Report 2005–5289, 98 p.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Approach
  • Data Collection
  • Development of the Predicted Bridge-Scour Database
  • Development of the South Carolina Pier-Scour Envelope Curve
  • Evaluation of Selected Methods for Predicting Clear-Water Pier Scour in South Carolina
  • Guidance for Evaluating Pier-Scour Depth in South Carolina
  • Development of the South Carolina Clear-Water Contraction-Scour Envelope Curves
  • The South Carolina Clear-Water Pier- and Contraction-Scour Database
  • Summary
  • Selected References
  • Appendix 1
  • Appendix 2

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Development and evaluation of clear-water pier and contraction scour envelope curves in the Coastal Plain and Piedmont Provinces of South Carolina
Series title:
Scientific Investigations Report
Series number:
2005-5289
DOI:
10.3133/sir20055289
Edition:
Version 1.0: Originally posted 2006; Version 1.1: August 31, 2016
Year Published:
2016
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
South Carolina Water Science Center
Description:
Report: x, 98 p.; Database
Country:
United States
State:
South Carolina
Online Only (Y/N):
Y
Additional Online Files (Y/N):
Y