Clearing the Harbour

Top – two men digging aither side of a barge (1920’s Harbour Trustees photo). The aerial shot of similar period shows three barges together near the back of the Victory suggesting perhaps a permanent mooring and therefore a permanent function – e.g., the regular scouring of the mud flats by hand near that point.
The old dredgers were perhaps unable to operate away from the main channel even at high tide until they got through the locks. The photo shows the barge outside the round marker bouys of the main channel.
Even dredging by hand gradually between hightides (common in Victorian times) over a period of time may well have been effective “for shovelling away by navvies called muckshifters…..” until relatively recent times when dredgers had more efficient mechanisms and shallower draughts as the whole area there inside and outside of the old main channel seems now to be maintained at 1.9 metres.
Is that what is happening here …. or have they just grounded?