Insights from Depth-Averaged Numerical Simulation of Flow at Bridge Abutments in Compound Channels

Two-dimensional, depth-averaged flow models are used to study the distribution of flow around spill-through abutments situated on floodplains in compound channels and rectangular channels (flow on very wide floodplains may be treated as rectangular channels). The study leads to useful insights regarding distributions of flow velocity, unit discharge, and boundary shear stress at spill-through abutments. It also presents insights from extensive assessment of uncertainty associated with the use of depth-averaged modeling of flow at abutments. Of substantial use for design determination of abutment scour at bridge waterways is estimation of the magnitude of peak values of flow velocity, boundary shear stress, and unit discharge in the region where scour develops. The study, by showing how abutment flow fields adjust in response to variations of abutment length, floodplain width, and main channel dimensions, yields important trends regarding the magnitude of amplification factors for depth-averaged velocity, unit discharge, bed shear stress, and distance to peak unit discharge. Early studies are shown to provide rather limited and inadequate amplification values associated only with a narrow range of abutment and channel geometries examined. The present study comprises a much broader range of abutment lengths, channel shapes, and floodplain dimensions than heretofore reported in the literature. The study’s insights, from its assessment of uncertainty associated with the use of depth-averaged modeling of flow at abutments, yield a relationship for estimating the optimum mesh size for use with depth-averaged models. The relationship is applicable to other subsequent studies using depth-averaged models of flow around abutments or similar hydraulic structures. Prior studies addressing the effect of mesh size on numerical error have not provided a recommendation for an average optimum mesh size. The study also gives focused recommendations for topics requiring further investigation.

  • Record URL:
  • Supplemental Notes:
    • This research is sponsored by the U.S. Department of Transportation, University Transportation Centers Program.
  • Corporate Authors:

    University of Wyoming, Laramie

    Department of Civil and Architectural Engineering
    1000 East University Avenue
    Laramie, WY  United States  82071

    Mountain-Plains Consortium

    North Dakota State University
    Fargo, ND  United States  58108

    Research and Innovative Technology Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Morales, Reinaldo
    • Ettema, Robert
  • Publication Date: 2011-7


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: 123p

Subject/Index Terms

Filing Info

  • Accession Number: 01354611
  • Record Type: Publication
  • Report/Paper Numbers: MPC Report No. 11-237
  • Files: UTC, TRIS, USDOT
  • Created Date: Oct 21 2011 7:38AM