Scour control at Outlook Bridge—A case study
This paper covers the chronology of events at the east abutment of Outlook Bridge on the South Saskatchewan River from 1936 to 1981. It traces the early discovery of deep scour, a failed attempt at remedial action, a model test, a successful solution with riprap, and later, the addition of a guide bank.Abutment scour on the prototype under flood conditions was observed to extend about 5 m below the footing, endangering the stability of the structure. Attempted remedial measures using bags filled with sand–cement were unsuccessful. An analysis of the river regime was undertaken and a 1:100 scale hydraulic model was constructed and tested. The model indicated that either a guide wall or riprap apron would give the required protection. Riprap was selected on the basis of least cost, but a guide bank was added at a later date to further improve conditions. Key words: bridge, scour, hydraulic model, riprap, guide wall, guide bank.