Year of the flood?
Is the weather getting weirder? It certainly feels like it, because 2017 is proving to be the year of the floods. Depending on how you count them, five or six states of emergency were declared in different parts of the South Island over the weekend to cope with heavy rain and flooding (Selwyn District called it twice in an escalating response).
With two months’ worth of rain falling in two days, parts of Christchurch, Selwyn, Timaru, Dunedin and wider Otago were either under water or threatened by the combination of heavy rain, rising rivers and tides. Roads were severed, evacuations ordered, houses flooded.
There have now been more than a dozen weather-related states of emergency declared in New Zealand this year – about equal to the entire previous decade.
Emergencies were called in April by various authorities in and around Whanganui, Rangitikei, the Bay of Plenty (twice) and Thames-Coromandel.
New Zealand has experienced this year the tail ends of Cyclone Debbie, Cyclone Cook, the ‘‘500-year’’ inundation of Edgecumbe, and now a two-day hammering of the South Island.
We occupy small islands in a very large ocean, so our weather has always been volatile, and we have always had bad years.
In 2004, for instance, a February ‘‘weather bomb’’ which caused floods and week-long disruption in Manawatu was followed five months later by days of rain and flooding in the Bay of Plenty.
But with climate change, it is predicted that our weather will become even more unpredictable. As the climate warms, we can expect events at the extreme ends of the scale – droughts and floods – to become more common.
The National Institute of Water and Atmospheric Research (Niwa) has reviewed international science on climate change to try to predict how it will affect New Zealand. Among other things, it reports that droughts will be longer and drier, but that extreme rainfall events will be more intense.
‘‘Rising sea levels and increasing heavy rainfall are projected to increase flooding and erosion in many coastal areas, particularly near river mouths, with escalating risks to many low-lying ecosystems, infrastructure and housing,’’ says Niwa in a climate change assessment report. ‘‘This is cause for serious concern given patterns of development and population distribution.’’
Not everyone takes long-term, or even short-term, forecasts seriously. When warnings about the weekend storm were issued last week, a comment section on stuff.co.nz filled up with people accusing forecasters of ‘‘crying wolf’’. They were proved wrong.
It would be unwise to close our minds to the possibility that the floods of 2017 might be a portent of things that will come more frequently and more dangerously. We should be talking about what can be done in the long term to increase our resilience when confronted with extreme and hazardous weather.
Perhaps there is some comfort in that authorities seem to be learning valuable lessons from other recent emergencies. Local authorities were quick to declare states of emergency after floodwaters began to rise on Friday, including two – Christchurch and Selwyn – which were roundly criticised for a tardy response to the Port Hills fire disaster in February. This is to their credit. No-one can afford to be complacent, because in the longer term the weather is going to get more extreme.