When the riverbed is very fine pebbles, when G is -2, -1.5, and -1, the pipeline is buried under the riverbed, and the bed surface is basically unchanged after scouring.
Under the condition that the river bed is very fine pebble, when G is -2, -1.5 and -1 respectively, the pipe is buried under the riverbed, and the surface of the bed is basically unchanged after flushing.