In 2009 New Zealand had 2,174 rail bridges and over 15,600 road bridges. There were 150 rail tunnels, totalling more than 87 kilometres in length. From 2000 to 2008 an average of over $9.7 million was spent annually on new road bridges.
Mountains and rivers
The high number of bridges and tunnels is due to New Zealand’s difficult terrain. Travelling inland involves crossing mountain ranges and gorges. The high rainfall and steep hill country create many rivers, which become wide and braided on the plains. The difficulty in crossing these rivers led to drowning being known as the ‘New Zealand death’ in the 19th century.
Changing types of transport
Māori and early Pākehā settlers largely travelled on foot, or by canoe up rivers, so they needed no more than occasional footbridges. To cross wide, deep rivers they used canoes or punts. Once people began travelling in coaches and transporting goods in carts, bridges became necessary. Many early bridges were only just the width of a cart. When the internal combustion engine arrived and two-lane highways were built, there was a need for more and wider bridges, although one-lane bridges remained common in rural areas.
The development of railways was a major reason for building bridges and tunnels. It was harder for trains to climb hills than it was for horses or automobiles, so railways needed tunnels.
New Zealand’s first significant tunnel was the rail tunnel between Lyttelton and Christchurch, built in the 1860s. When the Otago Central Railway was built through the Taieri Gorge in the 1880s, 16 new bridges were needed. When the Midland rail line was completed between Canterbury and the West Coast in 1923, it included 17 tunnels, five bridges and five viaducts. A number of bridges carried both road and rail; in 2009 three remained in use, out of 42 or more originally designed for both forms of transport. There were three double-storeyed bridges with the road underneath and the rail on top – at Seddon in Marlborough, at Ōkahukura near Ōngarue, and at Karangahake on the Paeroa–Waihī line.
The tunnel between Lyttelton port and Christchurch was built because large ships could not make it over the Sumner bar to reach the city. Elsewhere the need to keep rivers open for boats led to swing bridges, such as on the Heathcote River in Christchurch, while Auckland Harbour Bridge had to be high enough to let ships underneath.
Watery tunnel
New Zealand’s first tunnel is said to have been constructed in 1846 by James Crawford, who built a tunnel to drain water from his farm at Burnham Water, Wellington, into Evans Bay.
Other reasons
Bridges were constructed as cities grew. Christchurch was built on both sides of the Avon River, and Hamilton developed both east and west of the Waikato River. Before the Auckland Harbour Bridge was constructed, cars could only reach the North Shore on vehicular ferries, or by a long drive. Wellington was hilly and tunnels were built.
Gold miners built bridges to carry water races. Loggers often constructed rail tracks for bush trams to carry logs; on occasion these called for viaducts. The most spectacular examples were the four viaducts on the Port Craig bush line in Southland, including the Percy Burn viaduct, which was 125 metres long and 36 metres high. Power and sewerage schemes often required the construction of long tunnels.
