Non-metallic protective covers in the nature of interlocking panels of concrete for scour protection; non-metallic protective covers in the nature of interlocking panels of concrete for reducing or preventing scour or scour development; non-metallic protective ducting for scour protection; non-metallic protective ducting for reducing or preventing scour or scour development; non-metallic rigid protectors for cylindrical structures and cylindrical elements situated in close proximity to the se...