February 2020 flood: What will our future be with climate change?
This time last year, Milford Sound received 566mm of rain in a single day, stranding 380 people as rivers rose. It was more rainfall than the normal amount for the entire month of February, which is 455mm. The rain led to a State of Emergency being declared, first in Fiordland then to Southland, causing tens of millions of dollars in damage, the largest ariel rescue undertaken and people being displaced from their homes for months in eastern Southland. About 79 tracks in the Fiordland National Park were impacted during the flooding with great walks the Routeburn and Milford tracks both damaged and requiring extensive repairs. If there is one stark lesson from the flooding in February 2020 for the south, its that climate change is truly here. For sometime now scientists have predicted that we will experience more severe weather patterns and the February flooding was a fine example of it. DOC says under current climate projections, by 2040, this amount of rainfall in a single day will be a once-in-a-55-year event, and by 2090 it would be a once-in-a-27 year event. READ MORE: * Coronavirus: Regional council applies for $18m for stopbank funding * $19.7 million worth of insurance claims paid out for Southland floods * Coronavirus: Council sets up emergency operations centre in Gore DOC programme lead climate change adaptation, Sam Parsons, said the department has been working with NIWA climate change scientists to assess how climate change would impact its work. An assessment of Fiordland and Mt Aspiring National Parks using climate change projections shows that in the coming decades, the area can expect more heavy rain days, more hot days in inland and low elevation areas, and significantly less frost nights, Parsons said. After floods inundated the West Otago township of Kelso in 1978 and 1980, the decision was made to abandon the site of the town. Little remains of the once bustling township, and Emergency Management Southland team leader response Craig Sinclair said he couldnt rule out that the same thing could happen in parts of Southland. As climate change extends its grip, its possible that more intensive flooding events will mean that some homes may need to be moved. I'm sure that in the long-term some places will need to look at that. It comes down to how resilient a community is to flooding and how much they are prepared to put up with. Where those places are remains to be seen, but it wont be the first time thoughts had been given to moving people and property to higher ground. After the 1984 Southland flood some discussion was held about moving the main street of Mataura, but that hadnt eventuated, Sinclair said. And floodwaters swamping Wyndham forced residents to build flood protection from the Mataura River and the Mimihau Stream. The Mataura River at Gore peaked at 2400 cumecs during the February 2020 flood, which was the highest level since records began. It usually averages a far more sedate 65 cumecs. It led to the townships of Gore, Mataura and Wyndham being evacuated and a state of emergency being declared . NIWA has also carried out work to study the impacts of climate change in other areas of the province. In 2016, it published the Southland Climate Change Impact Assessment for Environment Southland, Invercargill City Council and the Gore and Southland district councils. It says that by mid-century, almost the whole Southland region is projected to experience increases in annual maximum five day rainfall of up to 15-30mm. The number of heavy rain days is expected to increase. Annual rainfall is expected to slightly increase by mid-century by five to 20 per cent, with a larger increase in the northern part of the region at the end of the century. The report says floods are expected to become larger everywhere. By the end of the century and with increased emissions, average annual river flows are expected to increase across the region up to 50 per cent in the Oreti and Mataura catchments. It makes for gloomy reading if you farm near a river, but Sinclair said the organisation had put basic community plans in place in areas affected by flooding. Community meetings had been held in places like Waikaia, Riversdale and Tokanui where there were often flooding events, so that people knew what needed to be done in an emergency, and how to keep safe. In rural areas, communities had to look after themselves because help may not arrive until flood waters receded. Our role in a flood is to make sure that people are aware of heavy rainfall coming in and making sure they have the ability and resources to keep them safe. Often you find that the stories about how people support each other are the things that people remember and talk about afterwards, rather than the flooding event itself. There are 458kms of stop banks and many hectares of designated flood spill zones throughout the province. Environment Southland has secured $18.5 million in shovel ready funding from the Government to upgrade the flood protection schemes in Invercargill and Mataura, and to repair flood damage in the Waiau catchment. Work is expected to start early this year. Environmet Southland team leader hydrological response Chris Jenkins said NIWA predicted the average maximum annual daily rainfall to increase by about 10 per cent throughout the region for the period 2031-2050. This could see an increase in the size of the average of the annual flood peaks by about 15 per cent, he said. However, NIWA had noted that this may not be a reliable indicator on the size of future rare flood events such as February 2020. Flood magnitudes and frequency in Southland are strongly affected by recurring climate patterns such as the Interdecadal Pacific Oscillation (IPO) which delivered swarms of floods from 1978 to 1999. This has phases that typically last 20 to 30 years and it is possible that we may enter another period dominated by large events. While flooding is the biggest natural disaster to threaten Southlanders, Sinclair said its not the only threat Emergency Management Southland is prepared for. The alpine fault earthquake, when it goes, will be a massive event for Southland and there is the risk of tsunamis out on the coast, but the main issue for us is flooding.