Many of New Zealand’s towns and cities are affected by flooding from rivers, lakes, overland flow, the sea and in some cases, a combination of all these. This guide is specifically focused on the effects of climate change on flooding from freshwater systems such as rivers and urban drainage systems.
Climate change is expected to influence flooding in a number of ways through changes in rainfall, temperature, sea level and river channel processes. These changes will exacerbate the existing effects of flooding on infrastructure, including:
Climate change effects on flooding may influence flood risk management priorities, and may even increase the risk from flooding to unacceptable levels in some locations. As a result, you will need to ensure your flood risk assessments incorporate the impacts of climate change on the flood hazard.
The guide comprises four parts:
Part One provides information on the key effects of climate change on flooding.
Part Two presents methods for estimating changes in rainfall, flow rates and inundation.
Part Three provides a method for considering the consequences of future flood risk within a risk management framework.
Part Four highlights principles and options for managing future flood risk.
Parts One and Two of this guide summarise a 95-page report Tools for Estimating the Effects of Climate Change on Flood Flow (‘the source report’). The report is available from the Ministry for the Environment website at www.mfe.govt.nz/publications/climate/climate-change-effects-on-flood-flow/index.html. This guide and its source report are not intended to form comprehensive guidance on how to manage flood risk. They aim to provide a picture of the impacts of climate change on river flow and flooding, and provide good practice information and guidance to help local authorities incorporate climate change impacts into flood risk management planning.
In addition to this guide and its source report, a range of complementary guidance is available on climate change and hazard management from the Ministry for the Environment. This includes:
The Ministry for the Environment also provides guidance for local authorities on a range of topics on the Quality Planning (QP) website (www.qp.org.nz/), including:
There are also other resources and guidance on aspects of flood risk management that may be of use such as council reports, good practice guides or international guidelines and methodologies. For example, a comprehensive guide on identifying methods for valuing the costs and impacts of risk management options in monetary terms can be found at the DEFRA websiteFootnote 1 as part of the UK best practice guides on coastal flood defences.
Preparing for Future Flooding is targeted at those of you who are involved in local government decision-making, in particular: