The palette
Water leads everything here, so give the two channels different treatments rather than one: a broad settled tone for the Floating Harbour, something quicker and more restless for the New Cut and the tidal river. The gorge to the west wants to go deep and dark, a recess rather than a feature. The centre is a dense grey with no regular weave to fall back on, which means your water has to do the organising. If you mark the motorway at all, let it be a single point stopping dead at the edge of the centre.