Flood protection intensifies with sea level rise of 1.35m expected in next 100 years


A police officer diverts traffic from a flooded Newlands Road in July.  (File photo)

KEVIN STENT / Stuff

A police officer diverts traffic from a flooded Newlands Road in July. (File photo)

Dams will be built higher and weir gates will be strengthened, as flood protection in the Wellington area intensifies in line with the latest climate science advances.

The new flood protection infrastructure will have to provide for a sea level rise of at least 1.35 meters, according to the guidelines proposed by the Greater Wellington Regional Council, as it plans to update its protection policy against flooding. flooding.

The Ministry of the Environment recommends that all new infrastructure take into account sea level rise of about 1.35 m by 2121 (a 100-year horizon) and an expected increase in precipitation of up to 30 % by 2120 in some watersheds. .

The policy of the regional council, presented Tuesday to the climate committee, will reverberate in the lives of residents through the district plans of local councils, some of which will be revised in the coming months, and which set the rules for what can be built and where.

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MARTEN RABERTS

Large waves hit the Esplanade between Ōwhiro Bay and Island Bay on Wellington’s south coast.

The current policy of the regional council was set in 2013; by the year 2100, rainfall intensity is expected to increase by 20 percent – 10 percent less than the new estimate – and sea level to rise by 0.8 m – an increase from the new estimate of 55 centimeters.

Regional Councilor Thomas Nash said: “The data has gotten clearer and it has gotten worse. “

Mitigation strategies will be undertaken basin by basin and will use the Representative Concentration Pathway (RCP) – a greenhouse gas concentration trajectory adopted by the IPCC – scenario 6 at least.

People walk and cycle along the Avalon Riverbank, Lower Hutt, but the infrastructure serves an important purpose in terms of sea and river level rise.  (Photo file)

John nicholson

People walk and cycle along the Avalon Riverbank, Lower Hutt, but the infrastructure serves an important purpose in terms of sea and river level rise. (Photo file)

An RCP 8.5 scenario will be used for work that protects assets of “great community importance” – the location of a new hospital or the protection of large populations.

The effects of climate change are expected to be an increase in precipitation, which means greater flows in rivers, severe storms becoming more frequent and less predictable (increased erosion of infrastructure) and a rise in the level of water. the sea reducing the effectiveness of coastal flood defenses.

Rising water tables will reduce the amount of water the soil can absorb, leading to increased runoff and higher river levels.

Before and after the Takarau Gorge Road, which connects Johnsonville and Makara with Wellington, after heavy rains flooded Ohariu Creek.  (File photo)

Provided

Before and after the Takarau Gorge Road, which connects Johnsonville and Makara with Wellington, after heavy rains flooded Ohariu Creek. (File photo)

Urban areas in the Hutt Valley, the coastal townships of Kāpiti, Masterton and Greytown in Wairarapa and rural areas in the region have been identified as particularly at risk.

The objective of this policy was to “provide solid research to communities, regarding their transportation, the infrastructure of their homes,” Nash said.

“The best we can do is prepare people in the best possible way. “


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