Local scour is of major concern for the stability and integrity of offshore pipelines. Considerable empirical predictive formulae on spatial and temporal development of scour below subsea pipelines have been proposed. They have been predominantly based on data sets from experimental studies that were often carried out through small-scale flume model tests in laboratories with potential scale effects, i.e., discrepancies between model and prototype responses. In the present study, physical modelling of two-dimensional scour was performed with a prototype-scale pipeline (diameter of 0.63m) bottom-seated on cohesion-less sediment under steady currents in a 5.0m wide, 8.0m deep, and 450m long mega flume facility. The spatial and temporal scour development was monitored through observation window and measured by an underwater ultrasonic ranging system. The present tests extended local scour data sets obtained in controlled experiments from small-scale models to a prototype scale, thereby furthering the flow field Reynolds number from sub-critical to transitional and super-critical regimes. The present prototype-scale physical modelling aims to serve as a benchmark case for research related to local scour below pipelines.

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