Flooding to rise fourfold this century, say scientists

Most New Zealand regions are likely to face more varied rainfall patterns through the century and floods will become four times more frequent because rainfall is likely to become more intense.

Scientists advising the Government's Climate Change Project say two regions which already have a subtropical climate with warm humid summers and mild winters, Northland and Auckland, are likely to become warmer and drier as global climate change continues.

Northland's average temperature could be up to 3C warmer over the next 70 to 100 years, compared with a temperature increase in New Zealand during the past century of about 0.7C.

Northland could be up to 10 per cent drier with more varied rainfall patterns, and flooding could become up to four times as frequent by 2070 in both Northland and Auckland, and at the same time, long drier summer spells would put pressure on water supplies.

In a summary of regional variations in the likely effects of climate change, the scientists said there were likely to be significant costs to the community. These could be boosted by extreme weather events becoming more frequent or severe, and costs and damages associated with them were also likely to increase.

"The cost of dealing with stock losses, replacing or repairing damaged roads, bridges, houses and stormwater drains, and dealing with increased soil erosion and loss of soil nutrients can be formidable," the scientists said.

Though farmers could benefit from better crop growing conditions and faster growth of pasture, it was likely greater fertiliser use would be needed.

In Waikato, which was relatively sheltered by high country, the warm, dry and settled climate during summer and fairly cool winters faced changes in average temperature, sea level rise and rainfall patterns.

Waikato was likely to have similar temperature lifts as Auckland and Northland, and be up to 20 per cent wetter with more varied rainfall patterns and flooding up to four times more frequent by 2070.

Similar patterns would be seen in the Bay of Plenty.

Taranaki, which has warm summers and reasonably mild winters, was also likely to become warmer and wetter with more varied rainfall patterns and more frequent flooding.

The Manawatu-Wanganui region - often windy because of its exposure to disturbed weather systems from the Tasman Sea - faced similar changes.

On the East Coast, where Hawkes Bay and Gisborne had predominantly warm, dry, settled weather in summer and mild winters, the climate was likely to become warmer and drier.

These regions could be up to 20 per cent drier, with dry periods interspersed with heavy rainfall - and more frequent flooding.

Wellington and Kapiti regions, which are often windy, have warm summers and coolish winters, while the Wairarapa region has predominantly warm, dry, settled weather in summer and relatively mild winters.

All three regions will be warmer and the west of the regions is likely to become up to 20 per cent wetter and eastern areas could be up to 20 per cent drier.

- NZPA

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