BACKGROUND
Since about 1990, significant resources have been devoted by state highway agencies and others to research on bridge scour. Research has been conducted in the following areas: (a) prediction of scour at bridge piers and abutments, (b) selection and design of bridge-scour countermeasures, (c) streambank protection, (d) tidal scour, and (e) analysis of river systems and methodologies for predicting channel instability.

In 1997, NCHRP Project 24-08, "Scour at Bridge Foundations: Research Needs," completed a comprehensive strategy to identify and guide bridge-scour-related research. In developing this strategy, it was necessary to assess the validity and applicability of research related to bridge scour and fluvial system instability; define the state of practice; identify gaps, deficiencies, and potential improvements in current scour technology; and make recommendations for future research. Using the comprehensive strategy developed under Project 24-08, the American Association of State Highway and Transportation Officials (AASHTO) has, through NCHRP, initiated and completed a number of bridge-scour-related research studies. In addition, agencies and institutions other than NCHRP have conducted bridge-scour-related research studies related to the comprehensive strategy.

The AASHTO Technical Committee on Hydrology and Hydraulics is currently developing two new manuals, "Policy for Design of Highway Drainage Facilities" and "Recommended Procedures for Design of Highway Drainage Facilities." To assist in development of the bridge-scour sections of these manuals, AASHTO needs a critical evaluation of bridge-scour research completed since 1990 with recommendations for the adoption of specific research results. These recommendations will be used by AASHTO in developing policies and procedures in the bridge-scour area for the two new highway drainage manuals.

OBJECTIVES
The objectives of this research are to: (a) critically evaluate bridge-scour research results completed since 1990, (b) make recommendations for adoption of specific research results into AASHTO policies and procedures, (c) recommend research needed to fill gaps where research results are not yet conclusive enough for adoption by AASHTO and wide-scale use by practitioners, and (d) draft the bridge-scour sections of the AASHTO manuals, "Policy for Design of Highway Drainage Facilities" and "Recommended Procedures for Design of Highway Drainage Facilities."


Accomplishment of the project objective(s) will require at least the following tasks.

TASKS

PHASE I (1.) Compile completed research in the functional areas listed in Special Note C. The compiled research
should include research sponsored by the NCHRP as well as by other agencies and institutions. (2.) Screen the research compiled in Task 1 and develop a list of specific research projects in each of the functional areas to be evaluated in Phase II. The screening process will result in a prioritized list based on a qualitative assessment that ranges from research that could be ready for incorporation into the bridge-scour sections of the AASHTO manuals, "Policy for Design of Highway Drainage Facilities" and "Recommended Procedures for Design of Highway Drainage Facilities" to research results not yet conclusive enough for adoption by AASHTO. (3.) For each of the functional areas to be evaluated, assemble an expert review team comprised of 2 to 5 persons with demonstrated expertise in the functional area. Submit the resumes of the proposed experts for approval by the NCHRP. (4.) Develop a detailed procedure for critically evaluating the technical adequacy, strengths, and limitations of bridge-scour research results. This procedure will be used by the research team and each expert review team during the Phase II critical evaluation. This procedure should also be suitable for use by AASHTO after completion of this project. (5.) Update and refine the work plan for completing Phase II of the research. (6.) Within 8 months of contract award, submit an interim report documenting the work completed in Tasks 1 through 4. The interim report shall contain, as a separate appendix, the Task 5 revised work plan for Phase II. Meet with the NCHRP panel to review the interim report, the revised work plan, the Task 2 prioritized list of specific research projects, and the Task 4 procedures for the Phase II critical evaluation. During the interim meeting, a list of projects will be finalized for critical evaluation in Phase II. Work on Phase II will not begin without approval of the NCHRP panel.

Phase II (7.) Critically evaluate the technical adequacy and limitations of the research projects approved during the Task 6 interim meeting. Document the strengths and limitations of the research results for each project. (8.) Develop draft recommendations for adoption and incorporation of specific research results into AASHTO policies and procedures. Clearly document the breadth of application and limitation of each recommendation. Document where research results are not yet conclusive enough for adoption by AASHTO and wide-scale use by practitioners and recommend specific research needed to fill the gaps. (9.) Submit a second interim report documenting the Task 7 evaluation and the Task 9 draft recommendations. The report should include the Task 7 draft recommendations as a separate appendix to the interim report. Meet with the NCHRP panel to review the second interim report. Work on Phase III will not begin without approval of the NCHRP panel.

Phase III (10.) In accordance with guidance from the NCHRP panel during the Task 9 interim meeting, finalize the draft recommendations. Based on the final recommendations, draft the bridge-scour sections of the AASHTO manuals, "Policy for Design of Highway Drainage Facilities" and "Recommended Procedures for Design of Highway Drainage Facilities" for consideration by AASHTO. (11.) Submit a final report that documents the entire research effort. Include the recommendations and AASHTO manual material as stand-alone appendixes.