Mangaeniu-Ohau River

Forest and Bird, Issue 107, 1 February 1953, Page 11

Mangaeniu-Ohau River

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By

BERNARD TEAGUE

MR. TEAGUE describes a little-known natural curiosity in the Urewera—a river which has carved itself an underground passage for a short distance, leaving its old bed of polished rock dry.

Cross a mountain range from the head of Lake Waikaremoana, drop down into the opposite valley and one finds the headwaters of the charming Mangaeniu-ohau River. This river from its very source, until it flows into the -Waiau River, lives its whole life in the bush and on its whole length the're is not one clearing. The total number of humans who have tramped down this lonely riverway would probably number less than twenty as it is unknown to all but a few Government deerkillers and a handful of trampers. The Mangaenui-ohau is a river .of waterfalls. Trampers who have had experience of waterfalls have found that such waterways are usually very irksome, either in ascent of descent and often require gymnastic efforts in rock climbing with a rope needed to raise or lower rucsacs. Although the Mangaeniu-ohau has so many waterfalls in its course that the tramper loses count of them, the passage down the stream bed is easy from a mountain tramping standard and" for from two to three days one meanders along revelling in the ever unfolding beauty. Apart from the large and varied falls and cascades on the main stream

many smaller waterfalls from tributary streams fall into the larger waterway. For good measure there is one star attraction that is freakish and unique. The river does a disappearing act, leaving its ancient riverbed dry while it disappears in a frothing cauldron of foam into an underground passage, to reappear at the bottom of a thirty foot cliff about 100 yards downstream. The reason for this stygian dive is found in the formation of the river bed. Running across the valley through most of its length are horizontal or transverse bars of a hard rock. These cause the many waterfall terraces. Where the river disappears the bars of rock are inclined horizontally. Between two of these bars the river over many centuries formed a deep trough and finally weakened the bottom of the trough until it found an underground passage. The high level riverbed of rock polished through the centuries is thus left bare.