Introduction

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:

• roading
• wastewater and stormwater systems and drainage
• flood mitigation works
• water supply and irrigation
• private and public assets, including houses, businesses, schools and production systems.

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 three parts:

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.

Supporting guidance

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:

• Preparing for Climate Change: A Guide for Local Government in New Zealand (2nd edition, 2008), and its source report, Climate Change Effects and Impacts Assessment: A Guidance Manual for Local Government in New Zealand (2nd edition, 2008)
• Preparing for Coastal Change: A Guide for Local Government in New Zealand (2009), and its source report, Coastal Hazards and Climate Change: A Guidance Manual for Local Government in New Zealand (2nd edition, 2008).

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:

• Climate Change Guidance Note
• Natural Hazards Guidance Note
• a number of articles relating to flood hazards in the QP library
• a report on natural hazard management in the QP research area.

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 website^{Footnote 1} as part of the UK best practice guides on coastal flood defences.

Target audiences

Preparing for Future Flooding is targeted at those of you who are involved in local government decision-making, in particular:

• strategic and policy planners
• asset managers charged with planning future asset needs for communities and resolving existing and emerging problems
• those responsible for natural hazards management, river management, emergency management, ‘lifeline’ utilities and infrastructure
• staff responsible for council databases, particularly those providing information on hazards and risks to private land owners and other agencies.