USGS-VDOT Bridge Scour Pilot Study
Cost effective and safe highway bridge designs are required to ensure the long-term sustainability of Virginia’s road systems. The water flows that, over time, scour streambed sediments from bridge piers inherently affect bridge safety and design costs. To ensure safety, bridge designs must anticipate streambed scour at bridge piers over the lifespan of a bridge. Until recently Federal Highway Administration (FHWA) guidance provided only for scour estimates of granular, non-cohesive, highly erosive material – yielding overestimates of scour potential in instances when streambed materials offer some resistance to scour.
As research into properties of streambed materials has advanced, methods of evaluating scour that incorporate scour resistance are now included in FHWA publications. Bridges with piers established in, or on, cohesive soil or erodible rock may now be designed so that the scour resistance of these materials is taken into account. These new and more complex design evaluations require knowledge of the duration of exposure of bed materials to scouring flows over the expected life of a bridge. Currently the established standards for evaluating hydrologic processes do not provide this type of information. As a step toward meeting this need, this pilot study seeks to explore methods to estimate duration of specific streamflows and potential cumulative stream power over the design lifespan of a bridge. This information may then be used to calculate comprehensive projections of anticipated scour rates specific to individual bridge piers. New knowledge of cumulative scour may provide significant bridge construction cost savings while ensuring design and construction of safe highway bridges.
Deliverables
The USGS Virginia Water Science Center (VWSC) is providing examples of compilation, calculation, and summation of hydrologic properties needed to determine potential rates of streambed scour using information from study test sites, along with hydrologic statistics, statistical methods, and hydrologic modeling methods. These examples may assist in evaluating and estimating future cumulative streambed scour at specific bridge pier locations over projected design lifespans. The Virginia Department of Transportation (VDOT) provides non-hydrologic elements essential to determining potential rates of streambed scour, such as bridge location and design specifications, attributes of cohesive soils associated with bridge piers, geotechnical attributes of bridge scour computations, and preferred specifications and methods for estimating soil scour.
Study deliverables include:
- Example analyses and evaluations of daily and instantaneous stream discharge data.
- Example hydrologic design products.
- Example hydraulic geometry characteristics.
- Example evaluations of discharge probabilities.
- Example simulation tools illustrating probabilistic and deterministic analyses of discharge–duration scenarios.
Links to Bridge Scour Pilot Study Publications.
Virginia Bridge Scour Pilot Study—Hydrological Tools
Examples of experimental tools developed during the pilot study.
Statistical modeling example.
Partners associated with this project.
Cost effective and safe highway bridge designs are required to ensure the long-term sustainability of Virginia’s road systems. The water flows that, over time, scour streambed sediments from bridge piers inherently affect bridge safety and design costs. To ensure safety, bridge designs must anticipate streambed scour at bridge piers over the lifespan of a bridge. Until recently Federal Highway Administration (FHWA) guidance provided only for scour estimates of granular, non-cohesive, highly erosive material – yielding overestimates of scour potential in instances when streambed materials offer some resistance to scour.
As research into properties of streambed materials has advanced, methods of evaluating scour that incorporate scour resistance are now included in FHWA publications. Bridges with piers established in, or on, cohesive soil or erodible rock may now be designed so that the scour resistance of these materials is taken into account. These new and more complex design evaluations require knowledge of the duration of exposure of bed materials to scouring flows over the expected life of a bridge. Currently the established standards for evaluating hydrologic processes do not provide this type of information. As a step toward meeting this need, this pilot study seeks to explore methods to estimate duration of specific streamflows and potential cumulative stream power over the design lifespan of a bridge. This information may then be used to calculate comprehensive projections of anticipated scour rates specific to individual bridge piers. New knowledge of cumulative scour may provide significant bridge construction cost savings while ensuring design and construction of safe highway bridges.
Deliverables
The USGS Virginia Water Science Center (VWSC) is providing examples of compilation, calculation, and summation of hydrologic properties needed to determine potential rates of streambed scour using information from study test sites, along with hydrologic statistics, statistical methods, and hydrologic modeling methods. These examples may assist in evaluating and estimating future cumulative streambed scour at specific bridge pier locations over projected design lifespans. The Virginia Department of Transportation (VDOT) provides non-hydrologic elements essential to determining potential rates of streambed scour, such as bridge location and design specifications, attributes of cohesive soils associated with bridge piers, geotechnical attributes of bridge scour computations, and preferred specifications and methods for estimating soil scour.
Study deliverables include:
- Example analyses and evaluations of daily and instantaneous stream discharge data.
- Example hydrologic design products.
- Example hydraulic geometry characteristics.
- Example evaluations of discharge probabilities.
- Example simulation tools illustrating probabilistic and deterministic analyses of discharge–duration scenarios.
Links to Bridge Scour Pilot Study Publications.
Virginia Bridge Scour Pilot Study—Hydrological Tools
Examples of experimental tools developed during the pilot study.
Statistical modeling example.
Partners associated with this project.