35th Pianc World Congress, Cape Town, 2024
The Manukau Harbour is located on the West Coast of New Zealand’s North Island in the Auckland Region. It has been identified as a potential greenfield port location to replace the cargo operation of the Ports of Auckland, which is located on the East Coast within the Waitematā Harbour. Exposure to large and persistent swell from the Southern Ocean and Tasman Sea, high tidal range, fast tidal currents, and a very large and shallow ebb tide delta at the Manukau Harbour entrance present several challenges to opening and maintaining a navigation channel in this location. Show more…To test the feasibility of the proposal, an in-depth understanding of the ebb tide delta dynamics and sediment transport mechanisms was needed. Using data collected from the field, satellite imagery, and a combined analytical and numerical modelling approach we have estimated capital dredge volumes and importantly rates of sediment infill to the channel at differing temporal scales from individual storms to annual rates and decadal evolution. It has been shown that the ebb tide delta has a rotational morphology over an approximate 20 to 25-year cycle which can affect the capital dredge volumes by up to 10M m3 depending on the position of the channel and banks within the cycle. A net movement of sediment from the south to the north through longshore processes have been shown to contribute 1.5M m3 / year to the system, however, it is the sediment recycled around the ebb tide delta through wave and tidal flows that look to govern the maintenance dredge requirement and therefore the viability of the harbour serving as a port location. Work is still progressing to finalise the technical feasibility of this. Show less…
