Submitted by admin on April 22, 2009 - 22:51
Tasman, the first white man to discover New Zealand, saw what he called a “land uplifted high”. The country's mountains, the narrow width from coast to coast, and a copious rainfall combined to make the planning and building of a communication system among the scattered settlements a most difficult task. There are very few navigable waterways, for most of the rivers fall quickly to the sea, with shallow rapids and frequent waterfalls. The 6,000–10,000 ft mountain sources lie always less than 100 miles from the nearest sea coast, and many rivers from 6,000 ft to sea level are less than 20 miles long.
Construction of roads and railways was put in hand very shortly after the first permanent settlers arrived in 1840. By 1880 most of the main lines of communication were completed. Between 1870 and 1880 Sir Julius Vogel carried out a large and vigorous public works and immigration programme to develop the country. This was the busiest bridge-building period New Zealand has ever seen. The early builders had to use untried materials and, very often, inexperienced staff and workmen. They did not at first realise the magnitude of floods and the scour and bank erosion which resulted. But despite these difficulties, the standard of workmanship in some of the early bridges – generally of timber – was very high. Some are still used to carry heavy modern vehicles. But with recent changes in transport loading, many of the bridges built in the energetic Vogel era have reached the end of their useful life. Strengthening and replacing them has become a major problem of the 1960s. It is worth noting that the durable but somewhat brittle totara timber became by the 1870s the only native timber used in bridging. Nowadays modern preservative treatments have made it possible to use locally grown Radiata species, at least experimentally, for bridges.
Some idea of the constant need for bridge building may be seen from the fact that, without including innumerable culverts and bridges under 25 ft long, there is now an average of 14 ft of bridging for every mile of formed road in New Zealand.