BRIDGE SCOUR IN THE COASTAL REGIONS

Bridge scour and waterway instability in the coastal region where waterways are subjected to tidal flow can be subjected to mass density stratification, water salinity, sedimentation (littoral drift or riverine transport), and unsteady reversible flows from astronomical tides and storm surges, as well as riverine flows. Nevertheless, bridge foundation scour depths can be determined and waterway instability can be countered by using existing scour equations and geomorphology techniques. A major difference for nontidal (riverine) streams is that the design discharge (50-, 100-, or 500-year return period flows) has a constant value, whereas with tidal waterways the design discharge for the same return periods may increase because it is dependent on the design storm surge elevation, the volume of water in the tidal prism upstream of the bridge, and the area of the waterway under the bridge at mean tide. If there is erosion of the waterway from the constant daily flow from the astronomical tides that increase the area of the waterway, the discharges can increase. An existing clear-water scour equation can be used to predict the magnitude of this scour, but not its time history. Recent experience indicates that this long-term degradation can be as large as 0.2 to 0.9 m/year.

Language

  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 249-260
  • Monograph Title: FOURTH INTERNATIONAL BRIDGE ENGINEERING CONFERENCE, SAN FRANCISCO, CALIFORNIA, AUGUST 28-30, 1995. CONFERENCE PROCEEDINGS, 2 VOLUMES
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00711731
  • Record Type: Publication
  • ISBN: 0309061091
  • Files: TRIS, TRB
  • Created Date: Sep 6 1995 12:00AM