The National Academies

NCHRP 21-07 [Completed]

Development of Portable Scour Monitoring Equipment

  Project Data
Funds: $299,938
Research Agency: Ayres Associates
Principal Investigator: James Schall
Effective Date: 5/2/2000
Completion Date: 12/31/2002
Comments: NCHRP Report 515 Portable Scour Monitoring Equipment

The findings of research conducted under this project are presented in NCHRP Report 515 , "Portable Scour Monitoring Equipment." NCHRP Report 515 provides specific fabrication and operation guidance for a portable scour monitoring device. The fabrication guidance is of sufficient detail to allow a highway agency to build a similar device. The report describes the results of detailed testing of the scour monitoring device at ten bridge sites in seven different states.

Scour monitoring at bridges is often necessary and can be a cost-effective measure for protecting the traveling public during floods. Although significant research and development of fixed scour-monitoring equipment has been completed, it is not feasible to install fixed scour-monitoring equipment on all bridges. Each year, many bridges are subjected to severe flood conditions and scour. Decisions about bridge closure are often based on streambed elevations around piers and abutments measured with portable scour-monitoring devices such as weights and echo sounders. In addition, portable scour-monitoring equipment and techniques are often used to verify the stability of riprap and other structural countermeasures. Although current portable monitoring equipment is adequate in many situations, common field situations occur where existing equipment is inadequate. Several Departments of Transportation have been unable to adequately monitor scour at bridges during severe flooding because of the limitations of the existing equipment. The result has been increased risk and liability, unnecessary bridge closures, traffic delays, and increased expenses.

Common scour-monitoring problems can be separated into two categories: difficult flow conditions, (e.g., high velocity, air entrainment in the water column, and high sediment concentrations) and difficult site conditions (e.g., high bridges, low clearance under bridges, floating debris, and ice accumulations). These problems are common during extreme flood conditions, when the need for streambed elevation information is most critical. Research is needed to develop improvements and/or alternatives to existing equipment and monitoring techniques in order to allow streambed measurements to be made in these conditions. Although echo sounders and weights are the most common kinds of equipment used, some conditions may require the use of other technologies. Portability, durability, ease of use, range of application, data recording, and cost are important considerations.

The research conducted under this project resulted in the development of a portable scour-monitoring device for use during flood conditions. The portable scour-monitoring device developed allows the determination of streambed elevations at bridge foundations during flood events or low-flow conditions.

Status: Research is complete.

Product Availability: The final report for this project has been published in the NCHRP report series as NCHRP Report 515, "Portable Scour Monitoring Equipment."

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