Debris causes hydraulic problems at highway bridges nationwide. The problems are the greatest in the Pacific Northwest and the upper and lower Mississippi River Valley. Debris hazards are local and infrequent phenomena often associated with large floods. Most bridge destruction is due to accumulation against bridge components. Debris may partially or totally block waterways and create adverse hydraulic conditions that erode pier foundations and bridge abutments and do other structural damage. Many debris problems exist in forested areas with active logging operations. Bridges on streams where stream slopes are mild or moderate, in contrast to headwater streams, are more vulnerable to debris related hazards. Debris hazards occur more frequently in unstable streams where bank erosion is active. Countermeasures presently used by highway agencies include: (1) sufficient free-board, (2) proper pier spacing, (3) solid piers, (4) debris deflectors, (5) special superstructure designs, (6) flood relief structures, and (7) regular and emergency removal of debris at bridge crossings. Most debris transported in floods does not travel a great distance and was observable locally along the streambanks upstream from the bridge prior to the flood. Rather than in congregations, debris moves as individual logs in a non-random path concentrating in the thalweg of the stream. Therefore, methods for evaluating its abundance and for mitigating its hazard are deemed feasible.

  • Corporate Authors:

    Tye Engineering Company

    9614 Jomar Drive
    Fairfax, VA  United States  22030

    Federal Highway Administration

    Engineering Research and Development Bureau, 1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Chang, FFM
    • Shen, H W
  • Publication Date: 1979-3

Media Info

  • Pagination: 71 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00311102
  • Record Type: Publication
  • Report/Paper Numbers: FHWA-RD-79- 62 Final Rpt.
  • Contract Numbers: DOT-FH-11-9274
  • Files: TRIS, USDOT
  • Created Date: Jun 9 1980 12:00AM