History – Harnessing nature’s power

Man’s adaptability and efficiency has been a double-edged sword throughout history. Attempting to overcome monumental problems has encouraged adaptations and innovation, but such endeavours have sometimes resulted in less than desirable outcomes.

One such example has been the adaptation of technology and techniques by the early New Zealand kauri bushmen, enabling them to effectively transport enormous logs using only the power of nature.

Two hundred years ago, much of the warmer north of New Zealand was cloaked in forest, above which the giant kauri, Agathis australis, towered. Much prized for the quality and beauty of its wood, the girth and straightness of its trunk, as well as the usefulness and beauty of its gum, the exploitation of kauri forests began, and the resulting materials extracted, shaped the development of Northland. By 1905, milling of kauri timber had reached its height, with only patches of less accessible bush remaining. By the 1990s, only four per cent of the bush cover remained.

For those involved in the early industry, the sheer size of the logs made transportation a logistical problem. However, it was identified that kauri is the only New Zealand native wood which is buoyant and floats. The adaptation of Southern Hemisphere logging technology was modified to the New Zealand situation.

Kauri dams were built high in the rugged hills of the bush especially to move the logs. Constructed from kauri timber, the dams were designed as barrier walls, to temporarily dam a stream. Through summer and autumn, trees were felled and skidded down to the cleared area, upstream of the dam wall. When the dam gate was opened, the awaiting logs were guided through and liberated in the resulting flash flood of released water. The strong flow of water drove the hundreds of waiting logs downstream to the sea. ‘Drives’ were usually held in winter when there was plenty of water to move the accumulated logs.

It was also common for the dams to be built, and released, in sequence along one stream, thus magnifying the force of the water.

Unfortunately, although the stream beds were cleared of debris many logs were jammed in the driving, and much timber was damaged as logs struck against rocks and tumbled over waterfalls. Despite this, the transportation technique was effectively utilised.

It is still possible to visit a few remaining kauri dam sites in Northland, the Coromandel and on Great Barrier Island. The Department of Conservation says one of the dams in the Tangihua Range, near Whangarei, is accessible with an easy 20-minute walk, through regenerating forest.

The Kauri Museum at Matakohe also houses a scale-model of a kauri dam. In addition, the museum is the guardian of a collection of Tudor Collins’ photos, recording the kauri timber industry at the turn of the 20th Century.