Mahurangi River

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Mahurangi River
Mahurangi harbour
Location
Country	New Zealand
Physical characteristics
Mouth
• location	Mahurangi Harbour

The Mahurangi River is a tidal estuary in northern New Zealand that widens into the Mahurangi Harbour before opening into the outer Hauraki Gulf. The Mahurangi Harbour is accessible by all craft and is a sheltered anchorage in all weathers with many small bays and islands. The river itself is extremely tidal and ranges in depth from below approximately 50 centimetres (20 in) at the channel entrance to approximately 150 centimetres (59 in) further upstream. At high tide, the river is accessible by larger craft.

History[]

Approximately 17,000 years ago during the Last Glacial Period when sea levels were significantly lower, the Mahurangi River flowed into the vast coastal plain that existed where modern Hauraki Gulf exists. The river met the Waitematā Harbour (then a river) east of Kawau Island, and flowed north-east between modern day Little Barrier Island and Great Barrier Island, eventually emptying into the Pacific Ocean north of Great Barrier Island.^[1]

In Colonial New Zealand, the river was the main link between the town of Warkworth and the rest of civilisation. The historic Portland Cement Works opened in 1884 beside the river^[2] and many scows and steamers used it to export the cement. The cement works was closed down some years ago and the ruins remain on the banks of the river behind what has become a marina.

Warkworth was originally known as Brown's Mill, in reference to the sawmill established by Brown on the banks of the Mahurangi when the area was just a timber camp. The timber was transported by the river and often consisted of kauri spars, which were commonly exported. Sandstone from NSW was used as ballast and this was dropped at the mouth of the river, where large quantities can still be found. The kauri spars were then loaded for the return trip to Australia.^[3]

Features[]

Nationally endangered southern right whales are known to come into the bay to rest or calve.^[4] There are two boat yards on the Mahurangi river: one by the Portland Cement Works ruins and one further upstream by Warkworth. These yards both offer haul-out and hardstand options for both small and large craft. The township of Warkworth at the rivers head has a collection of small cafés, supermarkets, other stores and a post office. There is a moderately large wharf with a floating pontoon by the waters edge, although the river all but dries out here at low tide. The river itself has many small tributary streams which enter at different points along its length.

A weir in the river, Warkworth

There are several waterfalls on the river. The navigable portion of the Mahurangi river ends at the lower-most falls near the western end of the village, where, since the 1860s, the river has been dammed twice and several bridges have been installed. In 1877, a tsunami from the 1877 Iquique earthquake elevated the tide by six feet in mere minutes.^[5] There are currently two bridges remaining: a concrete bridge installed in 1971, which was originally used for a tramway but is now a pedestrian bridge; and a more recent bridge with two lanes for traffic.

References[]

External links[]

• Photographs of Mahurangi River held in Auckland Libraries' heritage collections.

Coordinates: 36°25′28″S 174°41′32″E / 36.424489°S 174.692321°E / -36.424489; 174.692321