Understanding the effect of tidal turbines on local erosion of the estuarine bed is crucial for design and maintenance of turbines with stable foundations and assessment of their environmental impacts. This report describes the results of flume experiments on clear-water scour caused by a single cross-flow turbine in steady flow conditions. The turbine investigated is a Momentum Reversal Lift (MRL) turbine originally designed in collaboration with the University of Exeter. Results show that the turbine can cause significant bed scour. particularly when it was not spinning and in a particular orientation of blades. This is opposite to the previous findings for axial flow turbines. The bottom plate of the turbine, although increasing scour depth, was found to increase the turbine performance and reduce adverse effects on the downstream flow. The findings highlight the importance of regular monitoring and taking immediate repair actions for a tidal installation.