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4 Effects on local government functions and services

Key points:

Assessing the effects of climate change can be broken down into manageable steps, as follows:

  • Use Tables 4.1 and 4.2 to identify specific resource effects relating to identified functions and services, and associated climate variables.

  • If undertaking an initial screening analysis, use this information in association with material in chapter 5 (and its references to chapters 2 and 3 and Appendix 3) to evaluate whether climate change is likely to be a consideration in the particular area or issue. Then, decide on the need for further information and analysis.

  • Use Table 4.3 to identify relevant sources of information and expertise.

  • Identify, as far as possible, the limitations (assumptions and assessment capability) that exist.

  • Use the examples in Section 4.3 as a guide to summarising the above information for the particular area or issue.

  • Review any published information (Table 4.4) and, if appropriate, consult relevant experts (Table 4.3).

4.1 Introduction

This chapter provides guidance on identifying which local government functions and activities could be affected by the climate changes and fluctuations identified in chapters 2 and 3. It lists key climate influences and possible effects of climate change, for each of these functions and activities. It provides guidance on data, sources of information, models and specialist expertise in New Zealand that councils can use, along with the climate change scenarios covered by chapter 5, to quantify the likely magnitude of particular effects. Examples are given of some expected climate change effects, from studies that have been carried out in various parts of New Zealand.

The interactions between climate change and local government functions and services are likely to be quite complex. Identifying which effects are important in terms of responding now might seem quite a daunting task. However, assessing the effects of climate change can be broken down into manageable steps, as explained in chapter 1, and risk assessment can be used to guide judgements on where to focus adaptation effort (chapter 6). Practical hints are as follows:

  • Staff responsible for a particular council function or service should integrate consideration of climate change into their assessment and planning activities.

  • Prioritise and then focus on only those functions and services of importance to your council and for which climate change may have a material effect.

  • For a particular function or service, start out with a straightforward initial screening analysis using simple initial estimates of how climate factors relevant to this function may change (chapter 5). It is necessary to embark on a more detailed effects study only if this initial analysis indicates material climate change impacts or opportunities are likely.

4.1.1 Making use of this chapter

This chapter provides resource material to help users follow through the assessment steps outlined in the ‘Roadmaps’ at the beginning of this Guidance Manual. We recommend that you refer to Figures R1 and R2, and to the Risk Assessment chapter (particularly section 6.4) for background. There are two particular ways in which information from the current chapter can be applied:

(a) When assessing effects of climate change on a particular council function or responsibility (Roadmap Figure R1). In this case, examine the entry for this particular function in Table 4.1 and the related entries in Table 4.2 to identify key climate variables and possible climate change effects. Then, use Table 4.3 for guidance on sources of information, models and expertise for use in quantifying these effects, in combination with the climate scenario guidance from chapter 5.

(b) When identifying and prioritising climate change risks and opportunities across all council functions and opportunities (Roadmap Figure R2). In this case, most of the entries in Tables 4.1 and 4.2 should be examined; they will aid identifying the council functions possibly affected by climate change and the key climate influences on them. Once these functions have been identified, an initial screening analysis can be performed (the fifth box on the left of Figure R2), using scenarios from chapter 5 and information from Table 4.3.

4.1.2 Making use of Tables 4.1, 4.2 and 4.3

Central to these tables is the link:

Key climate influence - Possible effects

Table 4.1 looks at this relationship from the perspective of:

Who is affected That is, which function(s)/asset(s)/activity(ies) – primarily of interest to city and district councils

Table 4.2 looks at this relationship from the perspective of:

What is affected That is, which resource(s) – (primarily of interest to regional councils

Table 4.3 provides useful information for all councils.

Tables 4.2 and 4.3 both help the reader through an assessment:

  • by looking at the present and future (Table 4.2)

  • by identifying who has expertise and what tools could be used (Table 4.3).

In using these tables, keep in mind that climate change and its effects should be considered relative to other changes. Climate change will not occur independently of other future changes, including changes due to natural climate variability, and future social and economic changes.

4.2 Links between climate influences and possible impacts

Table 4.1: Local government functions and possible climate change outcomes.

Function Affected assets or activities Key climate influences Possible effects Section in Table 4.2 giving type/explanation of effects

Water supply and irrigation


Reduced rainfall, extreme rainfall events, and increased temperature

Reduced security of supply (depending on water source)

Contamination of water supply

See Rivers, Groundwater, Water quality, Water availability, Coastal areas. (Note that there are also rainfall effects in areas dependent on rain water.)



Increased rainfall

More intense rainfall (extreme events) will cause more inflow and infiltration into the wastewater network. Wet weather overflow events will increase in frequency and volume

Longer dry spells will increase the likelihood of blockages and related dry weather overflows

See Drainage




Increased rainfall

Sea-level rise

Increased frequency and/or volume of system flooding

Increased peak flows in streams and related erosion

Groundwater level changes

Saltwater intrusion in coastal zones

Changing flood plains and greater likelihood of damage to properties and infrastructure

See Rivers, Drainage, Coastal areas


Road network and associated infrastructure (power, telecommunications, drainage)

Extreme rainfall events, extreme winds, high temperatures

Disruption due to flooding, landslides, fallen trees and lines

Direct effects of wind exposure on heavy vehicles

Melting of tar

See Drainage, Natural hazards

Planning/ policy development

Management of development in the private sector

Expansion of urban areas

Infrastructure and communications planning


Inappropriate location of urban expansion areas

Inadequate or inappropriate infrastructure, costly retrofitting of systems

See particularly Rivers, Groundwater, Drainage, Coastal areas, Natural hazards

Land management

Rural land management

Changes in rainfall, wind, and temperature

Enhanced erosion

Changes in type/distribution of pest species

Increased fire risk

Reduction in water availability for irrigation

Changes in appropriate land use

Changes in evapo-transpiration

See Water availability, Erosion, Biodiversity, Biosecurity, Natural hazards

Water management

Management of watercourses/lakes/ wetlands

Changes in rainfall and temperature

More variation in water volumes possible

Reduced water quality

Sedimentation and weed growth

Changes in type/distribution of pest species

See Rivers, Lakes, Wetlands, Water quality, Drainage, Erosion, Biosecurity

Coastal management


Management of coastal development

Temperature changes leading to sea-level changes

Extreme storm events

Coastal erosion and flooding

Disruption in roading, communications

Loss of private property and community assets

Effects on water quality

See Coastal areas, Natural hazards

Civil defence and emergency management

Emergency planning and response, and recovery operations

Extreme events

Greater risks to public safety, and resources needed to manage flood, rural fire, landslip and storm events

See Natural hazards


Pest management

Temperature and rainfall changes

Changes in range of pest species

See Biosecurity, Biodiversity

Open space and community facilities management

Planning and management of parks, playing fields and urban open spaces

Temperature and rainfall changes

Extreme wind and rainfall events

Changes/reduction in water availability

Changes in biodiversity

Changes in type/distribution of pest species

Groundwater changes

Saltwater intrusion in coastal zones

Need for more shelter in urban spaces

See Groundwater, Drainage, Water availability, Biodiversity, Coastal areas


Management of public transport

Provision of footpaths, cycleways, etc.

Changes in temperatures, wind and rainfall

Changed maintenance needs for public transport (road, rail) infrastructure

Disruption due to extreme events

See Drainage, Natural hazards

Waste management

Transfer stations and landfills

Changes in rainfall and temperature

Increased surface flooding risk

Biosecurity changes

Changes in ground water level and leaching

See Biosecurity, Natural hazards


Transmission lines

Extreme wind, high temperatures

Outages from damaged lines

See Natural hazards

Table 4.2: Sensitivity of natural resources to present climate and climate change.

Natural resource Key climate influence Impacts of climate change Present sensitivity to climate



River flows likely to, on average, increase in the west and decrease in the east of New Zealand

More intense precipitation events would increase flooding (by 2070 this could be from no change, up to a fourfold increase in the frequency of heavy rainfall events)

Less water for irrigation in northern and eastern areas

Increased problems with water quality

Strong seasonal, interannual and interdecadal fluctuations (see the example in Box 4.1 at the end of section 4.4, on peak flows in Bay of Plenty)


Temperature and rainfall

Lake levels likely to increase, on average, in western and central parts of New Zealand, and possibly to decrease in some eastern areas

Higher temperatures and changes in rainfall, particularly in areas such as the Rotorua Lakes, could result in a range of effects, including:

  • an increased degree of eutrophication and greater frequency of algal blooms

  • altering of lake margin habitats, including wetlands, with either increased or decreased rainfall

  • negative impacts on aquatic macrophytes, particularly native species, if lake levels fall

  • a decrease in the range of trout with increased water temperatures

  • increased ranges of pest species (eg, carp), placing even more pressure on aquatic ecosystems

Seasonal and interannual fluctuations


Temperature, rainfall, sea-level rise

Coastal and inland wetlands would be adversely affected by temperature increases, rainfall increases or decreases and sea-level rise

Many already under threat



Little change to groundwater recharge is expected in eastern New Zealand, but increased demand for water is likely

Some localised aquifers in northern and eastern regions could experience reduced recharge. For example, small coastal aquifers in Northland would be under threat from reduced rainfall

Seasonal fluctuations; but at present, generally stable over the longer term

Water quality

Temperature and rainfall

Reduced rainfall and increased temperatures could have significant impacts on the quality of surface water resources in northern and eastern New Zealand

Lower stream flows or lake levels would increase nutrient loading and lead to increased eutrophication

Most sensitive during summer months and in drier years



Increased frequency of intense rainfall events could occur throughout New Zealand, which would lead to increased surface flooding and stormwater flows, and increased frequency of groundwater level changes

Natural year-to-year variation in the location and size of heavy rainfall events

Water availability


Decreases in rainfall, which are most likely in the north and east of New Zealand, coupled with increased demand, would lead to decreased security of water supply

Dry summers, or extended droughts


Rainfall and wind

Increased rainfall in the west, and more intense rainfall events throughout New Zealand, could lead to increased soil erosion, including landslides

Intense rainfall events can arise with subtropical lows, and localised low pressure cells


Temperature, rainfall, wind

Increased temperature, reduced rainfall and more frequent drying westerly winds (possible in the east) would lead to changes in distribution and composition of native forest ecosystems throughout New Zealand

Most vulnerable will be fragmented native forests in the north and east of New Zealand

An increased biosecurity risk, with invasive temperate and subtropical species, would also have negative impacts on native flora and fauna

Drought can have a severe impact, eg, some native vegetation was adversely affected in Hawke’s Bay with the 1997/98 El Niño drought


Temperature and rainfall

Even small increases in temperature will significantly increase the incidence of pest outbreaks in New Zealand, particularly in the North Island and the north of the South Island

Both existing and potential new plant and animal pests could become established more widely, even with a slight increase in temperature

Pest outbreaks can be triggered by specific weather events, or from steadily changing conditions, eg, spread of Tasmanian grass grub in Hawke’s Bay was triggered by the warmer, drier conditions in the late 1980s and early 1990s

Coastal areas

Sea-level rise, storm frequency and intensity, wave climate, sediment supply

Effects of sea-level rise and other changes will vary regionally and locally

Coastal erosion is likely to be accelerated where it is already occurring and erosion may become a problem over time in coastal areas that are presently either stable or are advancing

Short- and medium-term fluctuations in sea levels (ie, up to about 30 years) are dominated by ENSO and IPO variations


Temperature, rainfall, wind

Increased temperatures in Auckland might increase photochemical smog

Fewer cold nights may reduce particulate smog problems in winter in affected towns and cities


Natural hazards

Temperature, rainfall, wind

The general indications are that New Zealand could experience more climatic extremes in the future. These could include:

  • more intense rainfall events, and associated flooding, in most parts of the country

  • more frequent and/or intense droughts in the east

  • more damaging windstorms

  • more heat waves

  • increased fire risk in drier eastern areas

There have been more frequent and intense El Niño events in recent decades, possibly associated with the IPO. The worldwide cost of extreme weather damage has increased owing to a mixture of climatic, economic and social factors

4.3 Assessing effects – methods, data, sources of information

There are three main approaches to assessing the effects of climate change at regional and local levels in New Zealand:

  1. Modelling. These incorporate computer-generated scenarios of climate change. An example is modelling that links historical weather data and information generated from General Circulation Models (translated to New Zealand’s situation, see chapter 2) to a model of river flow. This approach can be readily applied to existing models and data used by hydrologists and engineers. A variation of this approach is to draw on historical data to determine possible effects in the future (for example, using information on past flood events to assess what the effects would be if floods comparable to those experienced in the past, such as those connected with El Niño-Southern Oscillation (ENSO) or different Interdecadal Pacific Oscillation (IPO) phases, become more prevalent).
  2. Expert opinion. Seeking expert opinion can involve the presentation of plausible scenarios of climate change for your region (chapters 2 and 3) to knowledgeable people in your region, or national experts, to seek their views. In a flooding example, analysis as in (1) above could be undertaken using the input of experts. Often (see Table 4.3), there may be insufficient data and capability to follow the modelling approach, and it may be necessary to rely strongly on expert opinion. For example, local pest management people will have a good knowledge of current pest problems, and will have the capability to provide ‘expert opinion’ on the likely effects of climate change.
  3. Monitoring. The real effects of climate change will be detected only through ongoing monitoring. In some cases, monitoring may be the only way that effects can be quantified over time. See section 7.9 for further discussion on monitoring.

When selecting the assessment method, some judgement will be required on which is most applicable to the problem or issue of concern. Considerable capability already exists for assessing physical impacts – in terms of expertise, data and quantitative models. For example, there is a strong capability in New Zealand for predicting river flows in many parts of the country. In general, there is a much lower capability for quantitative assessment of biological and social/human impacts. In areas such as asset management (where investment in infrastructure is required), quantitative modelling is the principal approach. For issues such as biodiversity, a combination of approaches may be necessary, with monitoring playing a very important role. A broad summary of the capabilities that exist for identifying the effects of climate change on key local government services and functions is provided in Table 4.3.

4.3.1 Uncertainties and assumptions

Whichever method or approach is chosen, there will be assumptions that are made and/or inherent uncertainties. These need to be taken account of, along with the uncertainties that presently exist in projections of future climate.

In a study by Lincoln Environmental (see Table 4.4) on the impacts of climate change on water resources,75 there were key assumptions made with the models that were used. For example, key assumptions made with the river flow model were:

  • There will be no hydrologically significant changesin vegetation (eg, no major conversions between pasture and forest).

  • There will be no new diversion or abstraction of river water (nor any new extraction of groundwater that sustains river flow).

Table 4.3: Data, sources of information and assessment capabilities relating to the effects of climate change.

Natural resource

Key climate influence

Source of information

Assessment capabilities




NIWA ‘Topnet model’, MIKE11; Lincoln Environmental (irrigation model)


Regional council water quality and quantity databases; National HIRDS dataset; National Climate Database; National River Water Quality and Quantity Network and Database; National Hydrometric Database

Good predictive capability in most cases



  • flooding

Peak rainfall and/or flows and/or levels

  • water quality

Seasonal rainfall and/or flows and temperature



  • lake levels


  • water quality

Seasonal rainfall and temperature

  • ecosystems

Decadal rainfall and temperature



  • ecosystems

Decadal rainfall and temperature



  • irrigation

Seasonal to decadal rainfall

Water quality

Daily to monthly temperature, rainfall


Rainfall, groundwater levels, land use

Storm water and waste water drainage

Hourly peak rainfall

Water supply and irrigation

Rainfall and/or flows, projected demands




CLIMEX (developed in Australia to predict distributions of insect pests); Landcare Research have a range of models for predicting biodiversity changes and ecosystem responses; CLIMsystems (an evolution of CLIMPACTS); Hotspots (mosquitoes)


National vegetation survey, soil and land databases (Landcare Research)

Some predictive modelling capability exists, principally in the science community. In many cases, it will be necessary to gather biological and physical data over a period of time.




Decadal rainfall and temperature


Seasonal to decadal rainfall and temperature




Various dynamic 1-, 2- and 3-D models and empirical models


Sea levels, winds, waves, tides, sea surface temperature, beach profiles


Saltwater intrusion into rivers and water supplies

Long-term changes in sea level
Increase in storm intensity and frequency
Changes in sediment supply
Changes in wave climate



CALPUFF and other dispersion models; TAPM
National Air Quality (NIWA/MfE) and National Climate Database

Specific modelling capability limited to a small number of experts
Limited current data at relevant scales

Air quality

Hourly temperature
Hourly wind speed and direction
Hourly solar radiation


24-hour to seasonal weather extremes (temperature, rainfall, wind, snow)



Natural hazards

Note: HIRDS is the High Intensity Rainfall Design System available on CD from NIWA, or (HIRDS Version 3) via the NIWA website.

4.4 Examples of what is known about effects

The following examples demonstrate how the information presented in the preceding tables might be drawn together. The summary information on effects comes from a variety of sources. In the first example relating to water allocation, results from a published study are briefly presented. In the other examples, information on effects is mostly based on the expert opinion of regional council staff. Finally, a brief example of the interrelationships between climate change and climate variability (in this case the IPO) is presented, drawing from an Environment Bay of Plenty study.

4.4.1 River flows and irrigation

Local government function: water allocation for irrigation

Natural resource: rivers

Key climate variables: 30-year time series of daily precipitation, maximum temperature, minimum temperature, dew point temperature, solar radiation and wind run

Climate change effects: reduced river flows possible in eastern New Zealand

Key risk: less surface water available for irrigation

Uncertainty: changes in river flows in catchments that reach into the Main Divide or central North Island are dependent on precipitation changes in these areas, which are uncertain

A study for the Tukituki catchment in Hawke’s Bay predicted that river flow would generally decrease by 2050 with climate change. Based on the climate change scenarios used, river flows would decrease by 20–30% in summer and autumn, and by 0–10% in winter. It was concluded that peak irrigation demand could increase by 10% by 2050, but that there would not be any change in irrigation days lost (principally because there is already a 100% frequency of occurrence of irrigation seasons with some irrigation time lost). This study was based on mean changes in climate and did not take account of the possible effects of changes in frequency or intensity of climatic extremes. (Source: Lincoln Environmental 2001.)

4.4.2 Erosion and landslides

Local government function: erosion control

Natural resource: land

Key climate variables: intense rainfall events

Climate change effects: increasing frequency of intense rainfall events

Key risk: increased erosion risk

Uncertainty: lack of regional detail

On the West Coast of the South Island an increase in rainfall would also increase the potential for landslides, and potentially landslide dam-break flood events, as occurred in the Poerua River catchment in 1998. (Source: West Coast Regional Council 2002.)

Erosion risk is high over significant tracts of land in Manawatu. For example, 500,000 hectares of hill country is at risk of accelerated erosion in Manawatu. This risk could be exacerbated with any increase in rainfall frequency and intensity. (Source: 2002.)

4.4.3 Water supply and demand

Local government function: water supply

Natural resource: surface and groundwater

Key climate variables: average rainfall (monthly, seasonal, annual)

Climate change effects: decreased rainfall in the north and east of New Zealand

Key risk: decreased security of water supply

Uncertainty: average decreases in rainfall appear more likely in the east of New Zealand than in the north

Peak daily water demand in Wellington is usually at the end of an extended dry, hot spell of 10 days or more. If such events increase with climate change, then the number of peak days can be expected to increase. (Source: Wellington Regional Council 2002.)

4.4.4 Biosecurity

Local government function: pest management

Natural resource: land

Key climate variables: temperature and rainfall

Climate change effects: increasing temperatures and rainfall changes

Key risk: increased biosecurity threats

Uncertainty: the rate and magnitude of climate change, which remain uncertain, will determine the extent of the problem

Warmer conditions in recent years have highlighted the sort of pest problems that are likely to arise more often in coming decades. For example, the tropical grass webworm, a wind-blown invader from Australia, has decimated all pasture species, in fact anything green, on the Aupouri Peninsula in the far north of Northland in recent years. There are several pest plants currently found in small or not very vigorous infestations in Northland that would become a serious pest, not only in Northland but also through other parts of northern New Zealand, if there were even a slight increase in temperature. (Source: Northland Regional Council 2002.)

Box 4.1: Effects of climate variability

A comment on IPO relationships with river flows from Peter Blackwood, Manager of Technical Services, Environment Bay of Plenty 2003.

IPO is much more strongly correlated than ENSO, particularly to flood flows. Attached are graphs from the December 2000 Environmental Data Summaries showing peak flow for Waioeka, Whakatane and Rangitaiki. These show abnormally large floods during the phase of IPO prior to the mid-1970s and following 1998. The period from the mid-1970s to 1998, on the opposite phase of IPO, was conversely very benign.

Figure Box 4.1: Annual maximum flow as a proportion of the mean annual flood for the Rangitaiki, Whakatane, Waioeka and Kaituna rivers in the Bay of Plenty 1950–2000.

Annual maximum flood flows as proportion of the mean annual flood for the Rangitaiki, Whakatane, Waioeka and Kaituna rivers in the Bay of Plenty from 1950 to 2000 are related to the phase of the Interdecadal Pacific Oscillation. Graphs for each river show abnormally large floods during negative phases of the IPO, with annual maximum flood flows up to 2.5 or 3 times the mean annual flood. In the intervening positive phase (1978-1999) there were few large flood events where flood peaks in the four rivers were no larger than 1.25 to 1.5 times the mean annual flood.

4.5 Published studies on effects and adaptation

Various studies and reports published since 2000 that have focused on climate change effects and adaptation in New Zealand are listed in Table 4. Some of these contain results from quantitative assessments (such as the CLIMPACTS report (Warrick et al 2001) and the Lincoln Environmental study (Lincoln Environmental 2001), and some are reviews of what is known, drawing from published studies and the knowledge of experts. Many of these reports, plus some further background material, are available through the Ministry for the Environment’s web page of local government guidance materials on climate change here (3 April 2008). There are still many gaps in knowledge about regional and local detail, along with the uncertainties that exist about future changes in climate.

Table 4.4: Reports on the effects of, and adaptation to, climate change in New Zealand.

Science reports

The effects of climate change and variation in New Zealand: an assessment using the CLIMPACTS system – Warrick et al 2001

National reports

A methodology to assess the impacts of climate change on flood risk in New Zealand – Gray et al 2005.

Assessment of the need to adapt buildings in New Zealand to the impacts of climate change – Bengtsson et al 2007

Australia and New Zealand (in Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change) – Hennessy et al 2007.

Australia and New Zealand (in Climate Change 2001: Impacts, Adaptation and Vulnerability, Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change) – Pittock and Wratt 2001

Changes in drought risk with climate change – Mullan et al 2005

Climate change adaptation: guidance on designing New Zealand’s built environment for the impacts of climate change – O’Connell and Hargreaves 2004

Climate Change Impacts on New Zealand – Ministry for the Environment 2001a

Climate change: likely impacts on New Zealand agriculture – Kenny 2001

Climate change: potential effects on human health in New Zealand – Woodward et al 2001

Implications of Climate Change for the Construction Sector: Houses – Camilleri 2000

Impact of climate change on long-term fire danger – Pearce et al 2005

Incorporating climate change into stormwater design: why and how – Shaw et al 2005

Linkages between climate change and biodiversity in New Zealand – McGlone 2001

Planning for climate change: effects on coastal margins – Bell et al 2001

Report on some implications of climate change to Department of Conservation activities – McFadgen 2002

Regional reports

Adapting to Climate Change in Eastern New Zealand: A Farmer Perspective – Kenny 2005

Adapting to climate change: A view from the ground – Kenny 2006

Climate Change: An analysis of the policy considerations for climate change for the Review of the Canterbury Regional Policy Statement – O’Donnell 2007

Climate Change and Land Management in Hawke’s Bay: A pilot study on adaptation – Kenny 2002

Impacts of climate change on agriculture water usage and water availability – Lincoln Environmental 2001

Meteorological hazards and the potential impacts of climate change in the Manawatu-Wanganui Region – Tait et al 2005

Meteorological hazards and the potential impacts of climate change in the Wellington Region: a scoping study – Tait et al 2002

The impact of predicted climate change on hazards in the Auckland Region: scoping study – Auckland Regional Council 2002

Forces Shaping the 21st Century: Climate Change/Natural Hazards – Auckland Regional Council 2006.

Local reports

Impacts of Climate Change on Christchurch – Christchurch City Council 2002

Project CARE: Impacts of Climate Change to the Wastewater Network Strategic Improvement Plan – North Shore City Council et al 2003

Note: Full citations for these reports, including web locations for many of them, are provided in the References section located immediately before the appendices in this Guidance Manual.

75 Lincoln Environmental 2001.