The bridge pier scour research evaluation report (NCHRP 24-27 (1)) is currently being finalized. The report examines the present state of knowledge regarding bridge-pier scour, evaluates the reliability of leading current methods to provide accurate estimates of design scour depth, and recommends a structured approach to scour-depth estimation for design use. The large variation in factors potentially influencing scour at bridge sites requires an approach sufficiently comprehensive to account for the more important individual parameter influences to be considered, yet that also treats pier scour from a systems-analysis perspective when the number of parameters is too numerous, or the parameters are insufficiently independent, to be described practically in terms of a series of individual parameter influences. The present evaluation shows that, while the individual scour influences of the many bridge waterway variables are now well understood for simple or standard pier designs, and that recently developed scour estimation methods attempt to encompass these influences, there are several sources of substantial complexity that complicate the development of reliable comprehensive design relationship for estimating scour depth at piers: ¿ Complexity of flow field ¿ The fundamental problem of simultaneously scaling three scales (flow depth, bed material size and, structure size) ¿ Variations in channel boundary materials ¿ Differences in pier structure ¿ The complicating interaction of pier scour and other boundary erosion processes , such as accumulation of woody debris, ice bridge over-topping, abutment proximity, channel morphology, bedforms ¿ The large number of parameters involved

The objectives of this research address several research issues whose resolution should enhance the reliability of scour depth estimation. The research issues fall into several categories: ¿ Fundamental processes inadequately understood. The issues primarily concern flow field capacity to erode the channel boundary, and the boundary¿s capacity to resist erosion; ¿ Complicating processes inadequately understood. The issues concern flow field capacity to erode the channel boundary, and the boundary¿s resistance to erosion; ¿ Development of reliable design methods. Testing of standard or common abutment forms subject to complicating design considerations; ¿ Development smart instrumentation and observation procedures for monitoring boundary and flow conditions at bridge waterways. The TFHRC Hydraulics Laboratory will collaborate on this proposed research and will provide Lab capabilities and technical assistance. The TFHRC Hydraulics Laboratory is planning to utilize a high speed recirculation flume for the tests identified. This will allow live bed scour experiments for flow velocities up to 5 times the critical velocity for a specific selected sediment size and to study the live bed peak carefully.

The scope of work consists of researching identified bridge pier scour issues to predict scour and to improve scour prediction equations. The research will be based on a combination of data obtained from the historical scour research literature, laboratory experiments, field-testing, data collection, and data evaluation.

The Federal Highway Administration will serve as the coordinator for this pooled-fund project. State DOT¿s will be solicited for their interest and participation in this study. FHWA will issue a task order contract to the support services contractor to conduct the study. Periodic reviews will be arranged to keep participating states and agencies up-to-date on current developments. These reviews may include meetings in Washington D. C. during the annual TRB Session, e-mail submittals and conference calls. Suggested contribution: $20,000/year