HSWT is 4.6 metres. Depth at low water varies according to the height of the water in the river, but the harbour never dries out. The harbour has a NAABSA (Not Always Afloat but Safe Aground) classification. Heights of Spring and Neap tides can vary with barometric pressure and wind direction. After periods of heavy rain or melting snow, a spate is experienced and this can considerably increase the height of the river and the strength of current.
Under normal conditions the tidal current rate is typically:
Half Flood: Spring 3 knots, Neap 1.5 knots
Half Ebb: Spring 4 to 5 knots, Neap 3 knots
Download Perth main navigation marks [PDF: 120 kb] - not to be used for navigation