Surrounded by ocean, New Zealand is regularly swept by weather systems that bring heavy rain. The country’s many rivers and streams can quickly become powerful torrents, bursting their banks and causing millions of dollars of damage each year.
Full story by Eileen McSaveney
Main image: A broken stopbank, Whirikino
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Why does New Zealand have floods?
Flooding happens quite often in New Zealand, for several reasons:
- Weather systems are constantly sweeping over the country’s narrow islands, bringing heavy rain.
- The many mountain ranges cause moist air to condense and produce more rain. Parts of the West Coast, near the Southern Alps, have more than 10 metres of rain a year.
- The country is criss-crossed by rivers and streams that come down from the mountains.
- Clearing native forest means that heavy rain quickly flows into the rivers.
From the 1840s, the Europeans who began arriving did not know there would be frequent floods. Gold diggers in Central Otago were often drowned or lost everything when rain-swollen streams swept their tents away. In 1863 over 100 lives were lost.
More recent floods
Most New Zealand towns and cities have river flood problems. Floods continue to cause chaos and misery, costing millions of dollars to repair. Between 1920 and 1983 there were 935 damaging floods.
Floods can happen very quickly. After a few hours of heavy rain a dry creek can become a raging torrent – called a flash flood. In 1938 the Kōpuawhara Stream near Māhia rushed through a camp of railway workers as they slept. Huts were hurled about, and 21 people died.
In February 2004 there were major floods in the lower North Island and Marlborough in the upper South Island. The Manawatū River burst its banks and helicopters rescued stranded victims. The cost was about $400 million. Then in July, Whakatāne and Edgecumbe were swamped after intense rain, and over 3,200 people were evacuated.
Can floods be prevented?
They can’t be totally prevented, but stopbanks and dams help control rivers. Regional councils check rainfall and water levels, issue flood warnings, and control how land is used in risky areas. Flood plains are likely to be regularly flooded, and it is foolish to build there.