Flood mitigation schemes: are they working in flood-prone areas?

Floods are the most frequent economically damaging natural hazard in New Zealand, and climate change and sea level rise are projected to increase their intensity and frequency. People are increasingly moving into populated places with elevated flood risk, where floods damage both dwellings and primary income sources.

Traintracks submerged in flood water

Economic losses from flooding are substantial in New Zealand and are projected to increase. Floods have caused almost $300 million in damages since only 2014 (not including the New Year floods of 2017/18), with particularly disruptive impacts on homes and farming.

The most common method of managing flood risk in New Zealand is through flood mitigation schemes, in which flood-related infrastructure is funded via targeted property rates and government budget. However, many of these schemes were implemented last century, with mounting evidence that land use and population changes render them insufficient for future risk. There is also a surprising lack of research on these schemes.

This research explores several important and new research questions related to flood mitigation schemes. We will explore whether or not all flood-prone settlements have schemes in place – and will catalogue and map flood mitigation scheme locations using regional council data. We’ll investigate whether flood mitigation scheme funding is adequate, by analysing data on flood damage claims and property rates data. This information will be used to identify possible improvements in the system.

We will also try to understand whether flood mitigation schemes are sufficient to protect exposed communities from increased flooding due to climate change. We’ll do this by investigating the costs and benefits of flood mitigation schemes, comparing flood risk management in areas with mitigation schemes to areas without such schemes.