The natural flow processes encountered in rivers and streams can cause severe scour around bridge piers and vertical abutments as well as bank failure. This destabilization leads to costly repairs and sometimes complete structural failures. During recent years, there has been a sharp increase in efforts to stabilize channels and prevent this problem. Two classes of solutions have emerged; armoring of the vulnerable area using riprap or other revetment materials and installing flow altering structures which counteract detrimental flow patterns upstream of the areas at risk. To this date however, scour prevention is far from an exact science and long-term effective strategies are difficult to predict.
The aim of this research is to determine specific design guidelines for in-stream flow control structures based upon controlled experiments rather than prescribed approaches based solely on experience. The final product will provide quantitative engineering guidelines based on input from site and flow conditions. This will allow future practitioners to confidently select the most appropriate structures as well as have reliable information on cost, maintenance, and flood response.
Review of case studies, previous experiments, and state highway department experiences will be used to select a small group of the most promising in-stream structures. Lab work will be conducted at the Baker Environmental Hydraulics Laboratory and the large scale setting at St. Anthony Falls Laboratory (SAFL) Outdoor StreamLab. The Virtual StreamLab numerical model will be used to determine the site-specific properties to be measured, the most appropriate structure, effective installation method, and the likely failure flow rate of each structure.
Sponsor: National Cooperative Highway Research Program
Photo: a stream barb, courtesy of Jon Fripp, USDA
Photo: a cross vane, courtesy of USDA-NRCS