Manukau Harbour - Geography

Geography

The harbour mouth is between the northern head ("Burnett Head" / "Ohaka Head") located at the southern end of the Waitakere Ranges and South Head at the end of the long Awhitu Peninsula reaching up from close to the mouth of the Waikato River. The mouth is only 1800 metres wide, but after a nine kilometre channel it opens up into a roughly square basin 20 kilometres in width. The harbour has a water surface area of 394 square kilometres. There is a tidal variation of up to 4 metres, a very substantial change, especially since the harbour, being silted up with almost 10 million years of sedimentation, is rather shallow itself.

Because of the large harbour area and narrow mouth between the Manukau Heads, tidal flow is rapid and a bar at the mouth makes navigating in or out of the harbour dangerous. New Zealand's most tragic shipwreck occurred on the bar in 1863 when HMS Orpheus ran aground in clear weather with a loss of 189 lives. For this reason, along with the harbour's shallowness, it is not Auckland's favoured port, and the facilities at Onehunga are not very large compared to the other Ports of Auckland facilities on the Waitemata Harbour on the northeast of the isthmus.

The harbour has three main arms. The Mangere Inlet at the northeast lies close to Auckland's central city area, with the inner suburbs of Onehunga and Te Papapa situated close to its northern shore. The Otahuhu and Mangere urban areas lie south of this arm, which is crossed by the Mangere Bridge. In the southeast is the Papakura Channel, which extends into the urban area of Papakura. In the southwest a further inlet known as the Waiuku River reaches south to the town of Waiuku. The harbour reaches into Mangere Lagoon, which occupies a volcanic crater. Auckland Airport is located close to the harbour's eastern shore.