Kaipara Harbour - Geography

Geography

The harbour extends for some 60 kilometres (37 mi) from north to south. Several large arms extend into the interior of the peninsula at the northeast of the harbour, one of them ending near the town of Maungaturoto, only ten kilometres (6 mi) from the Pacific Ocean coast. The harbour has extensive catchments feeding five rivers and over a hundred streams, and includes large estuaries formed by the Wairoa, Otamatea, Oruawharo, Tauhoa (Channel) and Kaipara. A number of small islands off the shoreline are connected to the mainland by mudflats at low tide.

The Kaipara Harbour is broad and mostly shallow, as it is formed from a system of drowned river valleys. The harbour shoreline is convoluted by the entry of many rivers and streams, and is about 800 kilometres (500 mi) long, being the drainage catchment for about 640,000 ha of land.

The harbour entrance is a channel to the Tasman Sea. It narrows to a width of 6 kilometres (3.7 mi), and is over 50 metres (160 ft) deep in parts. On average, Kaipara tides rise and fall 2.10 metres (6.9 ft). Spring tidal flows reach 9 km/h (5 knots) in the entrance channel and move 1,990 million cubic metres per tidal movement or 7,960 million cubic metres daily.

The harbour head is a hostile place. Big waves from the Tasman Sea break over large sandbanks about five metres below the surface, two to five kilometres from the shore. The sand in these sandbanks comes mainly from the Waikato River. Sand discharged from this river is transported northward by the prevailing coastal currents. Some of this sand is carried into the Kaipara harbour entrance, but mostly cycles out again and then continues moving northwards along the west coast. The southern sandbanks at the entrance are constantly accumulating and releasing this sand.

These treacherous sandbanks shift and change position, and are known locally as the graveyard. The graveyard is responsible for more shipwrecks than any other place in New Zealand, and has claimed at least 43 vessels—some say as many as 110.

In Māori mythology, the ocean-going canoe Māhuhu voyaged from Hawaiki to New Zealand and overturned on the northern side of the entrance. It was commanded by the chief Rongomai, who drowned. His body was eaten by araara (white trevally), and his descendants to this day will not eat that type of fish. The first European shipwreck was the Aurora, a 550-ton barque, in 1840, and the most recent was the yacht Aosky in 1994. Today, the remains of wrecks still become visible under certain tidal and sand conditions.

For this reason, the Kaipara is rarely used today for shipping, and no large settlements lie close to its shores, although many small communities lie along its coastline.