Detecting local scour using contact image sensors

The paper presents a novel contact image sensor (CIS) to monitor the local scour process around a model pile in water flows. The CIS is an optical sensor that tracks the evolution of the interface between sand and water based on the difference in the refelectivity of light from different media. A number of sensitivity tests are reported. It was found that the sensor reading is insensitive to the temperature in the range of 2–30°C and can provide reliable and continuous high accuracy measurements if suspended sediment concentration is lower than 40 kg=m3 without needing precalibrations. Furthermore, the sensor was found to successfully detect local scour development around a vertical pile under steady current and tidal current. The CIS sensors have the potential to be applied to field monitoring of local scour around subsea infrastructure.