Hydraulic Bridge Scour Analysis and Design

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It’s been estimated that 60 percent of all bridge failures in the United States result from scour and other hydraulic-related causes. A directive from the U.S. Department of Transportation’s Federal Highway Administration (FHWA) National Bridge Inventory Systems requires the periodic review of scour at bridges. Washington’s Clark County needed assistance in evaluating scour and vulnerability of more than 40 bridges throughout the county.

ESA provided an initial Phase 1 analysis of 11 bridges, ranking their vulnerability to scour and erosion. We researched the design of the bridge structure, evaluated the upstream and downstream conditions for indicators of scour and stream instability, assessed bridge capacity under flood conditions, and identified those bridges at risk and in need of further study. The Phase 2 analysis included an evaluation of hydrologic and hydraulic conditions, an estimate of theoretical scour potential, and riprap sizing. We used methods developed by the FHWA to perform all of these analyses and prepared reports documenting our findings. We worked closely with Clark County to review the analysis results and prioritize more than 30 of the at-risk bridges.

Following our assessment work, ESA developed countermeasure designs for at-risk bridges on Salmon Creek, including bridges 2 (Felida), 33 (Pleasant Valley), and 212 (J.C. Ward).  These bridges were considered at risk because of potential contraction and pier scour, with a heightened concern due to channel approach migration patterns in the vicinity of the bridges.  For these bridges we conducted hydraulic analyses, designed bioengineered bank treatments, and produced plans, specifications, and cost estimates. We provided permitting services including Biological Assessments, wetland determinations, floodplain permits, and quantities and figures for shoreline permits and Joint Aquatic Resource Permit Applications.

ESA’ technical analysis and countermeasure designs for Clark County’s bridges will help to prioritize project funding to keep the county’s bridge infrastructure intact. 

Specialized Services

  • Biotechnical bank stabilization and grade control
  • Construction observation and support
  • County and city regulations and mandates
  • Design specifications and construction bid packages
  • Engineering design and construction documents
  • Flood frequency analysis
  • Hydraulic scour analysis
  • Hydrologic and hydraulic modeling
  • In stream flow studies
  • Inventories and reporting
  • Large woody debris and in stream structures
  • Modeling and analysis
  • Monitoring
  • Post-construction monitoring