Overview
Scour and stream instability problems have always threatened the safety of our nation's highway bridges. Countermeasures for these problems are defined as measures incorporated into a highway-stream crossing system to monitor, control, inhibit, change, delay, or minimize stream instability and bridge scour problems. A plan of action, which can include timely installation of stream instability and scour countermeasures, must be developed for each scour critical bridge. Monitoring structures during and/or after flood events as a part of a plan of action, can also be considered an appropriate countermeasure.
Numerous measures are available to counteract the actions of humans and nature which contribute to the instability of alluvial streams. These include measures installed in or near the stream to protect highways and bridges by stabilizing a local reach of the stream, and measures which can be incorporated into the highway design to ensure the structural integrity of the highway in an unstable stream environment. Countermeasures include river stabilizing works over a reach of the river upstream and downstream of the crossing. Countermeasures may be installed at the time of highway construction or retrofitted to resolve scour and instability problems as they develop at existing crossings. The selection, location, and design of countermeasures are dependent on hydraulic and geomorphic factors that contribute to stream instability, as well as costs and construction and maintenance considerations.
While considerable research has been dedicated to design of countermeasures for scour and stream instability, many countermeasures have evolved through a trial and error process. In addition, some countermeasures have been applied successfully in one locale, state or region, but have failed when installations were attempted under different geomorphic or hydraulic conditions. In some cases, a countermeasure that has been used with success in one state or region is virtually unknown to highway design and maintenance personnel in another state or region. Thus, there is a significant need for information transfer regarding stream instability and bridge scour countermeasure design, installation, and maintenance.
The target audience for this course is structural, transportation, and other civil engineers who are interested in protecting bridges, culverts, and embankments from destructive hydraulic phenomena. The course material is based on the Federal Highway Administration (FHWA) Hydraulic Engineering Circular (HEC) 23, Volume 2 (FHWA-NHI-09-112).
Once you complete your course review, you need to take a multiple-choice quiz consisting of fifty (50) questions to earn PDH credits.
Specific Knowledge or Skill Obtained
This course teaches the following specific knowledge and skills:
- Countermeasure design for stream instability
- Designing embankment protection
- Designing protection for bridge piers
- Designing protection for bridge abutments
- Design procedures for granular and geotextile filters
- Riprap protection for bottomless culverts and wave attack
- Concrete armor units as a substitute for riprap
Course
Click on the following link to the PDF document to review the course material before taking the quiz for credit.
Countermeasures for Bridge Scour & Stream Instability: Design Guidelines
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