Climate change means more intense rainfall, more often, in many parts of Dunedin, New Zealand and the world. Adapting old stormwater systems to this future is a global challenge and one that we are working on locally, particularly in the low-lying South Dunedin.
Heavy rainfall challenges
The most immediate challenge for South Dunedin is from heavy rainfall events.
Dunedin is experiencing more long duration (greater than 18 hours) intense rainfall events than it did in the past. These rainfall events can produce more water than the existing South Dunedin stormwater system can cope with, especially with water running in from other catchments.
South Dunedin is part of a large natural catchment. This is divided up into blocks that drain stormwater independently from each other in small scale rain events. However, in larger events, rainwater from other catchments – especially those on nearby hills – runs down into South Dunedin.
Sea level/groundwater challenges
In the medium to longer term, rising sea and ground water will increase the flooding and ponding risks in South Dunedin.
Groundwater is the water found underground in the cracks and spaces in soil, sand and rock. South Dunedin has always had high levels of groundwater, which reduces the ability for rainwater to soak into the ground.
The Parliamentary Commissioner for the Environment’s report into sea level rise released in 2015 predicts that rising sea levels will continue to push up groundwater levels in South Dunedin. This means, over time, the ground will be able to absorb even less rain water.
Addressing these issues presents challenges, particularly because there is uncertainty about the extent of climate change and sea level rise. However, it also presents opportunities such as:
- Meaningful community engagement – climate change adaptation conversations are ongoing. We want to have meaningful, long-term discussions with the community about what is important to them.
- Future-focus – engaging with the community and looking ahead 50-100 years means there is a future focus, rather than just reacting to the here and now. That future focus creates opportunities to resolve other long-term issues in the area, such as poor-quality housing.
- No options are off the table – there are some exciting examples of increased ‘blue/green’ infrastructure in other parts of the world. As well as increasing resilience to climate change, these examples have provided social, economic and health benefits to communities.
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