FST2DH is FHWA's Two -Dimensional Hydraulic Model for modeling flows in floodplains and through complex bridge openings. The model was developed more than ten years ago and since that time many improvements have been made to computational procedures employed by the program. Additionally, much advancement have been to the types of computer hardware needed to solve the complex series of equations used by the program. Numeric algorithms for solving simultaneous series of equations have continued to evolve and computers with multiple cores that can speed up the solution times by a factor of ten are now the norm. From an engineering perspective, we are more frequently being asked to solve complex problems involving multiple bridge openings, different types of structures, multiple embankments that alter natural flow patterns, unsteady flows, sediment transport, and scour countermeasure design. Because of the increasingly more difficult types of problems that are routinely being encountered, the state-of-practice needs to continue to improve to keep pace.

The objectives of this research is to enhance the FHWA-FST2DH Model for Simulating Two-dimensional Depth-averaged Flow and Sediment Transport The research will address following needs: * Improve Equation Solution Schemes - Implement parallel versions of several popular iterative methods for solving systems of equations. This will allow much faster computation times thus increasing productivity and the application of more complicated solutions to complex surface water flows. * Update and Testing of Sediment Transport Algorithms - Existing sediment transport algorithms will be tested using both hypothetical cases and comparison to measured data from both laboratory experiments and onsite studies of scour at river bends and constrictions (such as bridge openings). Sediment transport formulas not currently included in the existing formula library will also be added. * Update of Bridge Pier Local Scour Calculations - Bridge pier local scour calculations will be updated to include the most recent HEC-18 procedures, as well as other optional local scour calculation methods not currently coded in the model. * Update FST2DH Manual this will include the following: o Descriptions of improved sediment transport algorithms. o An added appendix that describes sediment transport test applications and new sediment transport formulas. o An added appendix that describes use of new equation solution schemes. o An added appendix that describes solution parameter uncertainty estimate calculations and how they can be used in practical design of hydraulic structures such as bridges and river training works. o Conversion of current WordPerfect electronic format to Microsoft Word electronic format. This encompasses much more than an import/export operation from either WordPerfect or MS Word since all equations will need to be re-typed and the document will need to be reformatted completely.

The outcome of this Pooled Fund Study will be an improved and more capable version of FST2DH. It will take advantage of multi-core CPU and/or GPU processing which will allow the speed of solution to increase many times over what they are today. The new version will also have improved and more reliable sediment transport analysis capability and the already included pier scour computations will be updated to reflect current practice. An updated User's Manual will also be provided that will document the capability and any new features of FST2DH.

Suggested contribution: $20,000/year 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 Lakewood, CO or Washington D. C. during the annual TRB Session, e-mail submittals and conference calls. Person Developing the Problem Statement Larry Arneson, PhD, P.E., D.WRE Principal Hydraulic Engineer Federal Highway Administration, Resource Center 12300 West Dakota Avenue Lakewood, CO 80228 larry.arneson@dot.gov