Combining Individual Scour Components to Determine Total Scour

This report presents and documents the results of a study of how different components of bridge scour should be combined to obtain an improved estimate of total scour depth for bridge foundation design. The scour components are abutment scour, lateral contraction scour, pressure scour (vertical contraction scour), and pier scour. In current design practice, separate estimates of individual scour components are added as a conservative approach to estimating maximum scour depths. This method discounts the concurrent interactions among scour components that may result in more realistic scour depth estimates that are smaller than for the conservative approach of simple addition of components. The research approach consisted of experiments conducted at the Georgia Institute of Technology and the University of Auckland, and numerical simulations of the flow field executed at Cardiff University. Both live-bed and clear-water scour experiments were performed in large compound channels with movable sediment beds. Embankment/abutment lengths were varied from approximately 40% of the floodplain width to full blockage of the floodplain. Flow types of free flow through the bridge, submerged orifice flow, and bridge overtopping flow were investigated. Four categories of scour component interaction were identified, and a formula was proposed for estimating the maximum scour depth in each case based on the experimental results and validation with a few available field measurements. Numerical model results validated the physics of the scour component interaction and guided the development of the equations as well as the method for calculating scour prediction parameters needed in the scour prediction formulas. The findings indicate that current methods overestimate maximum scour depth from 20% to 45% at the 95% level of confidence, while approximately 80% of maximum scour depth estimates using equations developed in this study fell within ±10% of the line of perfect agreement.


  • English

Media Info

  • Media Type: Web
  • Edition: Contractor's Final Report
  • Features: Appendices; Figures; References; Tables;
  • Pagination: 289p
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 01665787
  • Record Type: Publication
  • ISBN: 9780309473262
  • Report/Paper Numbers: NCHRP Project 24-37
  • Files: TRIS, TRB, ATRI
  • Created Date: Apr 11 2018 10:25AM