Consideration of climate change is increasingly embedded in design practice in New Zealand, and is an essential part of stormwater design and flood risk management. In 2008, the Ministry for the Environment (MfE) published national guidelines for expected changes to temperature, rainfall patterns and sea level rise, and there are also District and Regional Council guidelines. MfE uses a furthest horizon of 2090, which is 100 years on from the base data analysis at 1990, while other guidelines use a variety of horizons, often shorter. We are now a quarter of the way to this 100-year horizon.
Precedents set by some recent project resource consents have taken the same “100-year horizon” approach, but applied it from expected project delivery dates, setting thresholds beyond MfE’s 2090 horizon, and not necessarily matching the horizons in other local guidance. As an example, the Mackays to Peka Peka Expressway project was set a 2115 horizon, with a need to generate five different climate change datasets:
It was concluded that a full suite of studies downscaling from global or national models was not practical or justifiable for the relatively modest extrapolation from published data. Instead, simplified pragmatic approaches were taken to generating each of the required datasets in a form suitable for compliance with resource consent requirements. The paper outlines the different techniques used for each of datasets, including peer review, and the application of these in the project design. The potential implications of the United Nations Framework Convention on Climate Change ‘Paris Agreement’ to increases in global average temperature of less than 2°C above pre-industrial levels is considered.