Sand transport, Wellington Harbour entrance, New Zealand

Abstract

Continuous instrumental monitoring of boundary conditions at the seafloor indicate that transport of sand in the entrance to Wellington Harbour occurs mainly during storms. Storm waves suspend sand which is then transported by tides and linear currents of storm origin. Tidal currents, the prevailing force in calm weather, are too weak to instigate transport. Interpretation of sediment distribution patterns determined in 1903, 1964–65 and 1974–75 indicate that sand is transported northward, presumably under the influence of southerly storms and associated water motions. Bathymetric changes, based on observations over the past century, reveal that most of the transported sand eventually accumulates at the northern limit of the entrance where up to 5 · 5 m of sediment, including mud derived from the harbour, has deposited.