Planning for risk - Incorporating risk-based land use planning into a district plan. J.G. Beban and W.S.A. Saunders

Transcription

1 Planning for risk - Incorporating risk-based land use planning into a district plan J.G. Beban and W.S.A. Saunders GNS Science Miscellaneous Series 63 August 2013

2 BIBLIOGRAPHIC REFERENCE Beban, J. G.; Saunders, W. S. A Incorporating a risk-based land use planning approach into a district plan, GNS Science Miscellaneous Series p. J. G. Beban, GNS Science, PO Box 30368, Lower Hutt 5040, New Zealand W. S. A. Saunders, GNS Science, PO Box 30368, Lower Hutt 5040, New Zealand Other publications in this series: Saunders, W.S.A.; Glassey, P.J. (comps) 2007 Guidelines for assessing planning policy and consent requirements for landslide prone land. Lower Hutt: GNS Science. GNS Science miscellaneous series p. Saunders, W.S.A.; Prasetya, G.; Leonard, G.S New Zealand's next top model: integrating tsunami inundation modelling into land use planning. Lower Hutt: GNS Science. GNS Science miscellaneous series p. Saunders, W.S.A.; Beban, J.S Putting R(isk) in the RMA: Technical Advisory Group recommendations on the Resource Management Act 1991 and implications for natural hazards planning. Lower Hutt: GNS Science. GNS Science miscellaneous series p. Saunders, W.S.A.; Berryman, K.R Just add water: when should liquefaction be considered in land use planning?. Lower Hutt: GNS Science. GNS Science miscellaneous series p. We welcome any feedback that you have regarding the risk-based approach to planning and this document. Please contact either of the authors in the first instance with any feedback that you may have. Institute of Geological and Nuclear Sciences Limited, 2013 ISSN ISBN

3 CONTENTS ABSTRACT... IV KEYWORDS... IV 1.0 INTRODUCTION METHODOLOGY DISTRICT PLAN NATURAL HAZARDS CHAPTER BACKGROUND Seismic Hazards Flood Hazard Rainfall Induced Slope Failure SUMMARY OF THE APPROACH UNDERTAKEN IN THE DISTRICT PLAN FOR THE MANAGEMENT OF NATURAL HAZARDS NATURAL HAZARD OBJECTIVES Objective - Risk based approach to Natural Hazards Objective - Provision of Natural Hazard Information Objective - To manage the risks from cumulative natural hazards Objective - To manage the risks from cascading natural hazards Objective - Account for vulnerable communities when considering natural hazards Objective - Protecting and enhancing natural features that reduce the consequences from natural hazards Objective - Reducing the flood hazard from the Waitau and Urban Valley Rivers Objective - Integrated approach to reducing the risks from natural hazards METHODS OF IMPLEMENTATION Rules Provision of information to and education of the community Financial Contributions Co-ordinating with Emergency Management Officers Building Act 2004 provisions ANTICIPATED ENVIRONMENTAL OUTCOMES RULES Flooding Rules Waitau and Urban Valley Rivers Fault Rupture Rules Tsunami Rules Liquefaction Rules Cascading Hazard Rules Cumulative Hazard Rules Slope Failure Rules...32 GNS Science Miscellaneous Series 63 i

4 3.7 MONITORING OUTCOMES Model change in risk Resource consent and building consent decisions Compatibility with the Urban Valley Emergency Management Group Plan Measuring readiness through the provision of information Development and Financial Contributions CONCLUSION ACKNOWLEDGEMENTS REFERENCES FIGURES Figure 1 Five step risk-based planning approach (adapted from Saunders, et. al 2013)... 3 Figure 2 Demonstrating how the risk-based land use planning approach is consistent with an international risk management process (Standards New Zealand 2004; Standards Australia/New Zealand 2009) TABLES Table 1 Purposes of key legislation for the management of natural hazards (emphasis added) (Saunders and Beban 2012) ii GNS Science Miscellaneous Series 63

5 APPENDICES APPENDIX 1: RISK-BASED APPROACH A1.1 STEP 1: KNOW YOUR HAZARD A1.2 STEP 2: DETERMINE SEVERITY OF CONSEQUENCES A1.3 STEP 3: EVALUATE THE LIKELIHOOD OF AN EVENT A1.4 STEP 4: TAKE A RISK-BASED APPROACH A1.5 STEP 5: MONITOR AND EVALUATE A1.6 CONCLUSION APPENDIX 2: RISK ANALYSIS AND COMMUNICATION TASKS IN A RISK-BASED APPROACH TO LAND USE PLANNING APPENDIX 3: CALCULATING THE RISK FROM CUMULATIVE AND CASCADING NATURAL HAZARDS A3.1 CUMULATIVE NATURAL HAZARDS A3.2 CASCADING NATURAL HAZARDS APPENDIX FIGURES Figure A 1 Consequence table (adapted from Saunders, 2012) Figure A 2 Likelihood table with qualitative and quantitative descriptions (adapted from Saunders 2012) Figure A 3 Quantifying consequences and likelihood (adapted from Saunders 2012) Figure A 4 Qualifying levels of risk from Figure A 3 (adapted from Saunders 2012) Figure A 5 Colour coding the matrix based on level of risk (adapted from Saunders 2012) Figure A 6 Level of risk and associated consent status ( Figure A 7 The risk-based planning framework (adapted from Saunders 2012) APPENDIX TABLES Table A 1 Three different natural hazards and their associated likelihoods and Annual Exceedance Probability GNS Science Miscellaneous Series 63 iii

6 ABSTRACT This report presents an approach for incorporating risk-based land use planning into a New Zealand district plan chapter. The risk-based approach has been developed as part of a PhD thesis by Wendy Saunders (Saunders, 2012) and has been further refined under an Envirolink Tools project. The risk-based approach allows for the considered of both the consequences and the likelihood of a natural hazard event as opposed to the traditional planning approach of considering only the likelihood of an event. The district plan chapter has been prepared for Urban Valley, a fictitious urbanised city in New Zealand. The district plan chapter is an example of how an integrated riskbased approach can be used when making land use planning decisions. The objectives and policies of the district plan chapter identify the risk outcomes for natural hazards in Urban Valley. The corresponding rules have been developed based on the risk to existing and future development, while ensuring that the risk outcomes sought under the objectives and policies are achieved. It is assumed these rules are associated with hazards zones, shown on planning maps. These hazards zones show the extent of an area affected by a natural hazard, based on a likelihood determined by the council. The district plan chapter also sets risk-based anticipated environmental outcomes, methods of implementation and monitoring approaches and outcomes. This example is not intended to be a model chapter that can be used in all district plans by all local authorities. Rather, it is seeking to show that a comprehensive riskbased approach to planning for natural hazards can be undertaken under the existing legislative framework in New Zealand. KEYWORDS Land use planning, risk-based planning, natural hazards, district plan, good practice iv GNS Science Miscellaneous Series 63

7 1.0 INTRODUCTION This report presents an approach for incorporating risk-based land use planning into a district plan chapter, for an existing urbanised environment. The current approach to land use planning in New Zealand largely focuses on the likelihood of an event, with little consideration of the resulting consequences when the event exceeds the design level of the development. Furthermore, the current planning approach for natural hazards often uses terms such as acceptable risk, however, acceptable risk is not nationally defined within a planning context. This has resulted in developments being approved which actually increase risk, as the developer or property owner has been willing to accept the risk with little regard, at times, as to whether the community as a whole is willing to accept the risk, especially the cumulative risk that amasses with each poor planning decision. A risk-based planning approach considers both the consequences and likelihood of natural hazard event occurrence. The advantage of a risk-based assessment is that it allows for consideration of the risk associated with both the construction of buildings and a change in use to an existing building. This in turn allows for more robust planning decisions to be made when determining the risks arising from natural hazards on a particular development/activity (Saunders and Beban 2011). The risk-based planning approach that has been used to develop this draft district plan chapter has been developed in the context of the existing New Zealand legislative framework. The key pieces of legislation that manage natural hazards have a consistent focus on sustainable management or development, and refer to the social, economic and cultural well-beings, as well as health and safety (Table 1). The consequence assessment of the risk-based planning approach considers these well-beings. GNS Science Miscellaneous Series 63 1

8 Table 1 Purposes of key legislation for the management of natural hazards (emphasis added) (Saunders and Beban 2012). Statute Resource Management Act 1991 (Part 2, Section 5) Building Act 2004 (Part 1, Section 3) CDEM Act 2002 (Part 1, Section 3) Local Government Act 2002 (Part 1, Section 3d) Purpose To promote the sustainable management of natural and physical resources. Sustainable management means managing the use, development, and protection of natural and physical resources in a way, or at a rate, which enables people and communities to provide for their social, economic, and cultural wellbeing and for their health and safety. To provide for the regulation of building work, the establishment of a licensing regime for building practitioners, and the setting of performance standards for buildings, to ensure that (a) people who use buildings can do so safely and without endangering their health; and (b) buildings have attributes that contribute appropriately to the health, physical independence, and wellbeing of the people who use them; and (c) people who use a building can escape from the building if it is on fire; and (d) buildings are designed, constructed, and able to be used in ways that promote sustainable development. To improve and promote the sustainable management of hazards in a way that contributes to the social, economic, cultural, and environmental wellbeing and safety of the public and also to the protection of property Provides for local authorities to play a broad role in meeting the current and future needs of their communities for good-quality local infrastructure, local public services, and performance of regulatory functions. When considering the legislative context it is also important to recognise that the Government is considering changing the Resource Management Act 1991 to ensure that natural hazards are better accounted for in the land use planning process (Saunders and Beban 2012). In particular, feedback has been sought on the inclusion of risks from natural hazards as a consideration under Part II of the Resource Management Act 1991, as well as a s.106 matter (which would also be expanded to cover all resource consent applications). These changes would require risks from natural hazards to be considered as part of all land use planning decisions including resource consent applications and district and regional plan formation/changes, and during the formation of Regional Policy Statements. The risk-based planning framework which this chapter is based upon is consistent with these recommended changes to the Resource Management Act 1991, and would support councils with implementing a risk-based land use planning approach. A risk-based approach to land use planning is based around five steps (Figure 1), consistent with international risk management process (ref ISO 31000:2009) (Figure 2): 1. Know your hazard; 2. Determine the severity of the consequences; 3. Evaluate the likelihood of an event; 4. Take a risk-based approach; and 5. Monitor and evaluate. 2 GNS Science Miscellaneous Series 63

9 Figure 1 Five step risk-based planning approach (adapted from Saunders, et. al 2013). Figure 2 Demonstrating how the risk-based land use planning approach is consistent with an international risk management process (Standards New Zealand 2004; Standards Australia/New Zealand 2009). GNS Science Miscellaneous Series 63 3

10 For the risk-based approach to be effective, councils need to have high quality hazard information. This information should be in a format suitable for land use planning purposes, and allow for the creation of hazard zones. These zones should be based on the hazard that the Council decides to land use plan for. In some instances these zones will be delineated by the hazard (for example fault rupture zones) and in some instances the likelihood of the hazard (for example flood hazard zones). To assist in prioritising what hazards should be included in land use planning, it is recommended that the regional civil defence emergency management group plan is used as a guide, as these documents prioritise the hazards in a regional based on the risk they present. By linking the district plan chapter with the regional emergency management group plan it ensures that there is common risk reduction goals across the various council plans and policies, thereby allowing for a holistic approach to be undertaken to the management and reduction of the risks associated with natural hazards. 4 GNS Science Miscellaneous Series 63

11 2.0 METHODOLOGY The risk-based planning approach has been developed as part of a PhD thesis by Wendy Saunders (Saunders, 2012). This risk-based approach has been further refined under an Envirolink Tools project, with significant input from a number of central and local government organisations across the New Zealand. This Envirolink project is developing and presenting the risk-based planning approach as an online toolkit. As part of this project, a steering group was established with representatives from a variety of organisations including: Ministry for the Environment; Ministry of Civil Defence Emergency Management; EQC; Local Government New Zealand; Hawkes Bay Regional Council; Bay of Plenty Regional Council; Massey University; Thames-Coromandel District Council; Auckland Council; and Brendan Morris Consultancy. This steering group provided advice and direction on the development of the risk-based planning approach. Based on the final version of the risk-based planning approach, a district plan chapter was developed to demonstrate how a risk-based approach can be incorporated into land use planning. This district plan chapter has been reviewed by the members of the steering group as well as by a number of planners from the following organisations: Bay of Plenty Regional Council; Massey University; Tauranga City Council; Gisborne District Council Thames-Coromandel District Council; Whakatane District Council; and Local Government New Zealand. Following the feedback from these parties, the chapter was then reviewed internally within GNS Science. The comments and feedback from all parties have been considered and in many cases have been incorporated into the final version of the district plan chapter, which is presented in this report. GNS Science Miscellaneous Series 63 5

12 The example district plan chapter is intended to provide a best practice guide as to how a risk-based approach could be incorporated into a district plan. While the objectives and policies take an all hazard approach, the rules that have been developed are very contextual to the hazard environment of Urban Valley an urban environment with very limited prospects for greenfield development. This scenario has been used as it can be more challenging to reduce risks to existing urban areas, rather than greenfield areas, where hazards can be avoided. This district plan example is not intended to be a model chapter that can be used in all district plans by all local authorities. Rather, it is seeking to show that a comprehensive risk-based approach to planning for natural hazards can be undertaken under the existing legislative framework in New Zealand. When developing district plan rules, they need to be specific to the hazard and associated risk environment which they relate to. This chapter considers the following hazards: Seismic hazards: Rupture of the Grand Fault; Tsunami generated from a local and distant sourced fault rupture; and Liquefaction. Flood hazard: Waitau River; and Urban Valley River. Rainfall induced slope failure. It is acknowledged that there are other hazards which need to be planned for i.e. coastal erosion, and earthquake induced slope failure. A risk-based approach similar to that described below could also be undertaken for these hazards. To provide some context to Urban Valley, the district plan chapter starts by describing the hazard environment of Urban Valley. While this information would not be expected to be included in a district plan chapter, it does provide context regarding the hazards which this district plan chapter has been based upon. 6 GNS Science Miscellaneous Series 63

13 3.0 DISTRICT PLAN NATURAL HAZARDS CHAPTER 3.1 BACKGROUND Urban Valley is an existing urbanised city that is geologically dynamic region, with a variety of physical features including steep hills, low lying valley floors, river systems, and coastline (harbour and open coast). These features expose Urban Valley to a variety of natural hazards. The Urban Valley Emergency Management Group Plan identifies the following hazards as presenting the greatest risk to Urban Valley: Seismic hazards: Rupture of the Grand Fault; Tsunami generated from a local and distant sourced fault rupture; and Liquefaction. Flood hazard Waitau River; and Urban Valley River. Rainfall induced slope failure. The Urban Valley Emergency Management Group Plan identifies the above natural hazards and ranks them based on the risk they present to Urban Valley. The Urban Valley Emergency Management Group Plan also identifies the likelihood for each hazard. To ensure there is a consistent approach to risk reduction between the district plan and the Urban Valley Emergency Management Group Plan, the hazard zones for the aforementioned hazards are mapped in the district plan based on the likelihoods in the Urban Valley Emergency Management Group Plan. Furthermore, the planning responses in the district plan (i.e. objectives, policies, rules, methods, and monitoring provisions) address the risks from the hazards identified in the Urban Valley Emergency Management Group Plan. This approach ensures that there are consistent risk reduction goals across the various council plans and policies. These hazards are described in more detail below: Seismic Hazards Located along the western edge of Urban Valley is the Grand Fault. On average this active fault produces a 7.8 magnitude earthquake with a shaking intensity of up to MM 10 on the Modified Mercalli scale once every 880 years (Annual Exceedance Probability of % per year). This fault subjects Urban Valley to a variety of seismic hazards including fault rupture, ground shaking, liquefaction, slope failure, and tsunami. Fault Rupture The land on either side of the Grand Fault is expected to be permanently deformed when the fault ruptures. A fault rupture has the potential to cause significant damage to buildings and lifelines, and could result in injuries and loss of life. It is therefore important that developments either avoid being constructed over the Grand Fault as per the Active Fault GNS Science Miscellaneous Series 63 7

14 Guidelines (Kerr, Nathan et al. 2003), or be designed and constructed to accommodate/mitigate this hazard. The Grand Fault rupture zone has been identified on the District Plan maps. This fault rupture zone is 100m wide to accommodate the inferred position of the Grand Fault. This inferred position represents the current understanding on the location of this fault line. When assessing applications for new development in the Grand Fault rupture zone, the applicant shall provide a report from a suitably qualified professional that identifies the position of the fault, and any mitigation measures to reduce the risk from fault rupture. Ground Shaking The differing geological materials under Urban Valley influence the severity of the potential ground shaking from an earthquake. Urban Valley is divided into four zones, which are based on the classes under the NZS :2004 (Part 5: Earthquake actions New Zealand). These zones are ranked as follows: Class B Rock. This class is limited to the Hinemoa and Ngahere Hills Class C Shallow soil sites. This class is largely located to the north of Wandering Rivers and along the fringe of the valley floor alongside the Hinemoa and Ngahere Hills. Class D Deep or soft soils. This class is the majority of the valley floor from Wandering Rivers southwards. Class E very soft soils >10m in depth, former swamp deposits. These soils may be located from Central Urban Valley, southwards. generally located and includes the suburbs of Bay View, Hatterville, Little Heritage, and Spreading Waters Liquefaction Urban Valley has several suburbs that have soils that have either a high or very high susceptibility to liquefaction. In the event of an earthquake that has a peak ground acceleration of 0.1 or greater, it is expected that these soils could experience liquefaction. These soils are largely located in the suburbs of Little Heritage, River View and Bay View. Liquefaction has the potential to result in significant damage to buildings and lifelines located in these suburbs due to subsidence, differential ground settlement, and lateral spreading. Tsunami Urban Valley is susceptible to both local and distant source tsunami. Urban Valley has experienced several historical tsunami events including a 1.2m high tsunami that occurred in 1901 as a direct result of the Western Urban Valley Earthquake. This fault, in addition to the Grand Fault, presents a significant tsunami risk, with wave heights of approximately 2m - 3m expected when an offshore rupture of these faults occurs. The tsunami would arrive approximately 20 minutes after the earthquake without sufficient time to allow for an official warning. Due to this, land use planning measures are important to ensure that there is effective reduction of the consequences from a locally sourced tsunami. While a distant source tsunami is expected to occur more frequently than locally generated tsunami, the associated consequences from a distant source tsunami are considered to be less for the following reasons: 8 GNS Science Miscellaneous Series 63

15 The tsunami wave from a distant source event is likely to be lower (approximately 1m high); Early warning of these events is possible and the response measures in the Urban Valley Emergency Management Group Plan will be able to be implemented to reduce the health and safety consequences from these events; and By undertaking effective land use planning for a larger, locally sourced tsunami, the risk from the smaller distant sourced tsunami is inherently reduced Flood Hazard Urban Valley contains two rivers, the Waitau and Urban Valley Rivers, with the Urban Valley River being the larger of the two. The Urban Valley River is a short (approximately 53 km) steep river that drains the Northern Mountain Range. Due to the short steep nature of the river, the flood peak arrives in Urban Valley six hours after the rainfall. However, the flood peaks are relatively short. As a result of historic floods, the Urban Valley River has had extensive physical protection measures installed along its length. These physical works include the construction of stopbanks, channel control and the installation of rip rap and groynes. These works provide varying levels of protection, with some areas protected from a 1:440 year flood event and some areas having protection for a 1:100 year flood event. However, there is an on-going programme to upgrade all flood defences to ensure they protect for the 1:440 year event. Located on the inside of the Urban Valley River stopbanks are a variety of recreational activities. These activities contain few buildings, and in the event of a large flood, the resulting consequences are relatively low. However, on the outside of the stopbanks, the level of development in Urban Valley is relatively intense and includes retirement villages, early childhood facilities and critical buildings, the Urban Valley CBD and residential housing. Waitau River is located on the eastern side of Urban Valley and is smaller than Urban Valley River, with a total stream length of 9 km. The majority of the Waitau River catchment is covered by residential and industrial activities. In particular, the lower reaches of the Waitau River passes through a significant industrial zone that contains a large number of hazardous facilities. The main stream channel is highly confined and is concrete lined in places. As such, the capacity of this river is only sufficient to contain approximately a 1: 20 year flood event Rainfall Induced Slope Failure Urban Valley is bounded by the Ngahere and Hinemoa Hills. These hills are generally steep and are bisected by small streams. The geology of these hills can be generally described as weathered greywacke. These hills are covered in a mix of vegetation, including large areas of gorse, native vegetation (both regenerating and mature) and residential amenity planting (particularly in the residential suburbs). While there are several extensive areas of land vested as reserve, there are also large areas of the hillside that have been converted into residential development. Many of these residential properties contain steep land that could be prone to failure in high intensity rainfall events. GNS Science Miscellaneous Series 63 9

16 3.2 SUMMARY OF THE APPROACH UNDERTAKEN IN THE DISTRICT PLAN FOR THE MANAGEMENT OF NATURAL HAZARDS Development in Urban Valley (whether private or public) shall be undertaken in a manner that addresses the risk associated with the identified hazards. For the purposes of this District Plan, risk shall be defined using the following equation: Risk = consequences x likelihood of the natural hazard event The objectives, policies and rules in this chapter promote a risk-based approach to manage the relationship between development and natural hazards. The majority of the proposed objectives and policies apply to all natural hazards, though several hazard specific objectives and policies have been developed. The objectives and policies of the district plan require the following risk outcomes: No development shall give rise to an intolerable level of risk, regardless of the potential economic or social benefits that may arise from the development; The risk to developments in areas subject to existing tolerable risk shall be reduced; and In areas that are currently not developed, new development shall not result in risk that exceeds an acceptable level. The acceptable, tolerable and intolerable risk levels have been determined using the riskbased process and the associated matrix in Appendix 1. The resource consent categories have been based in the level of risk to existing and future developments in the various natural hazard zones. Development is defined as subdivision and any physical works, including (but not limited to) Earthworks The construction of new buildings, Additions and alterations to existing buildings, where these are outside the existing building envelope Installation of lifelines, Changing the use of a building in a manner that would increase the potential number of occupants, and The relocation of building(s) onto a site. Mitigation can be used to reduce the consequences from natural hazard events. Any mitigation measures proposed as part of an application need to be clearly identified and an assessment of their effectiveness shall be provided. Through collaboration between the Regional Council, District Council and the community, the risk from various natural hazards and areas of Urban Valley has been identified. Based on the risk, appropriate consent categories have been assigned to development, and guidance has been provided in relation to mitigation measures. 10 GNS Science Miscellaneous Series 63

17 3.3 NATURAL HAZARD OBJECTIVES Objective - Risk based approach to Natural Hazards A risk-based approach will be undertaken for all development in areas that are susceptible to the following natural hazards: Seismic hazards Fault rupture of the Grand Fault; Tsunami generated from a local and distant-source fault rupture; and Liquefaction. Flood hazard Waitau River; Urban Valley River; Rainfall induced slope failure. Any new development in areas susceptible to one or more of the above natural hazards shall ensure that the following health and safety, economic, built, social and cultural risk levels are achieved: No development shall give rise to an intolerable level of risk, regardless of the potential economic or social benefits that may arise from the development; The risk to existing developments in areas subject to intolerable and tolerable risk shall be reduced; and In areas that are currently not developed, new development shall not result in risk that exceeds an acceptable level. Policies a) All development in natural hazard zones shall consider the potential risks to health and safety, the built environment, and the risks to social, cultural and economic wellbeing arising from the development. b) An even weighting shall be applied to the potential social, built, cultural, economic, and health and safety consequences associated with the development, with the highest consequence being used to determine the risk associated with a development. c) Where there is uncertainty associated with the risks from natural hazards, a precautionary approach shall be undertaken until further detailed information on the extent and nature of the hazard becomes available. d) Any assessment shall identify the mitigation measures (if any) that are being used to reduce the risk from the development and the effectiveness of these mitigation measures. e) Cumulative or cascading hazards and their associated risks shall be considered. GNS Science Miscellaneous Series 63 11

18 Explanation Part II, Section 5 of the Resource Management Act 1991 requires councils manage in a way that enables people and communities to provide for their health and safety, and their social, and economic and cultural well-being of their communities. To achieve these outcomes, the District Plan takes a risk-based approach to manage the relationship between development and natural hazards. The District Plan identifies the areas of Urban Valley that are susceptible to the various identified natural hazards. Based on the risk in these various areas, appropriate consent categories have been assigned to development. This ensures that the risk to future developments can be holistically considered to ensure they achieve the risk outcomes sought by this objective and policies. At the time of undertaking development, mitigation measures may be required to reduce the consequences associated with the natural hazard. Such measures could include minimum floor heights (flooding), compaction of soils or specific foundation design (liquefaction), evacuation routes (including vertical evacuation) (tsunami), and the development of buffer zones (flood, landslide and fault rupture). Any mitigation used shall ensure that the levels of risk described in this policy are achieved and shall not increase the consequences from natural hazard events on any other property. When assessing developments where the economic risk is either acceptable or tolerable, consideration will be given to the secondary economic benefits that the development presents to the region. The following matters may be considered as ways to balance primary and secondary risk: 1. A development shall result in a level of economic benefit to the Urban Valley economy so that it significantly offsets any economic losses as a result of a natural hazard event; and 2. Mitigation measures are included into the design of new developments to ensure that the economic consequences associated with a natural hazard event are minimised. These measures should ensure that the potential downtime / non-operational time of the activity following the event are minimalized and the effects from the natural hazard on the operational ability of the development are reduced as low as reasonably practicable. When assessing the ability for the development to operate after an event, consideration needs to be given to the effect of the hazard on the lifelines and utilities beyond the boundaries of the site, which the development is reliant on Objective - Provision of Natural Hazard Information To ensure that the information Council holds regarding natural hazards is publicly available and can be used with the assessment of the risks to health and safety, the built environment, social and cultural and economic wellbeing of the Urban Valley community. Policies a) The known extent of the flooding, seismic, slope instability hazard zones will be identified on the District Plan Maps. b) Council will continue to undertake research on the relevant natural hazards and shall make this information publically available once it has been received. c) Any hazard information the Council holds on a property (including in the District Plan) will be provided in LIMs; 12 GNS Science Miscellaneous Series 63

19 d) Developments being undertaken in hazard zones shall include reports from suitably qualified professionals which identify the health and safety, built environment, social, cultural and economic risks arising from their development. Explanation The calculation of risk requires sufficient information to be provided about a natural hazard. The Urban Valley Council will, in collaboration with the Regional Council and the community: Identify the hazard zones in the District Plan; Quantify the existing risk in the hazard zones; Quantify the potential risk from future selected development scenarios in the hazard zones; and Determine the consent categories for any new development on the basis of the existing and potential future risk from development being undertaken in these identified areas. While not required under the Local Government and Official Information Act 1987, the Council will, as part of best practice, provide any relevant hazard information as identified in the District Plan, in any LIMs its issues New development may need to provide site specific assessments that will clearly identify the health and safety, built environment, social, and cultural and economic risks. The need for these assessments will be undertaken on an application by application basis and shall be determined by considering the following: The size of the development; The potential consequences that could result from the development; The nature of the natural hazard(s) that the development will be susceptible to; The vulnerability of the future occupants of the development; and The intended final use of the development and its function within the local community. Any risk assessments will clearly identify, through quantifying the risk, whether the proposed development will increase the risks when compared to the existing development on the site, and identify what mitigation measures are being incorporated into the development to reduce the consequences from natural hazard events. Council may require these reports to be peer reviewed Objective - To manage the risks from cumulative natural hazards The cumulative risk shall be considered in situations where two or more un-related natural hazards affect people and property. Development in cumulative hazard zones shall achieve the following health and safety, economic, built and social and cultural risk levels: No development shall give rise to an intolerable level of risk, regardless of the potential economic or social benefits that may arise from the development; The risk to existing developments in areas subject to intolerable and tolerable risk shall be reduced; and In areas that are currently not developed, new development shall not result in risk that exceeds an acceptable level. GNS Science Miscellaneous Series 63 13

20 Policies a) Developments shall identify the cumulative natural hazards that affect a site; b) Developments shall include an assessment of the associated health and safety, economic, built, social and cultural consequences arising from each natural hazard. c) The combined probability of the occurrence of the natural hazards shall be determined. d) Developments shall achieve the risk outcomes sought under this objective. e) Developments shall clearly identify the mitigation measures that have been used to reduce the risks arising from the natural hazards. Explanation Cumulative hazards involve multiple unrelated natural hazards affecting a property or area. There are areas in Urban Valley that are susceptible to several natural hazards that are not related. For example Spreading Waters is susceptible to liquefaction from a large earthquake and flooding from the Waitau River. As the natural hazards are unrelated, it is unlikely that any given area would be affected by all of the natural hazards at the same time. However, as the area is susceptible to multiple natural hazards, there is a higher likelihood that the land area will experience a natural hazard event. Therefore, areas that are subject to cumulative hazards have a higher susceptibility to natural hazard events, and therefore have a higher risk (the formula for calculating cumulative risk is contained in Appendix 3). The cumulative hazard zones have been identified on the District Plan maps. The hazards have been mapped at the likelihoods as identified in the Urban Valley Emergency Management Group Plan. A risk-based approach will be undertaken when considering a development on properties that are susceptible to two or more unrelated natural hazards. This approach will ensure that developments achieve the risk outcomes sought under this objective and policies Objective - To manage the risks from cascading natural hazards The cascading level of risk shall be considered where two or more natural hazards arising from the same single trigger event affect people or property. Development in the cascading hazard zones shall achieve the following health and safety, economic, built, and social and cultural risk levels: No development shall give rise to an intolerable level of risk, regardless of the potential economic or social benefits that may arise from the development; The risk to existing developments in areas subject to intolerable and tolerable risk shall be reduced; and In areas that are currently not developed, new development shall not result in risk that exceeds an acceptable level. Policies a) Developments shall identify the cascading natural hazards that affect a site. b) Developments shall include an assessment of the total health and safety, economic, built, social and cultural consequences arising from the cascading natural hazards. 14 GNS Science Miscellaneous Series 63

21 c) An assessment of the annual likelihood for the trigger natural hazard shall be provided d) Developments shall clearly identify the mitigation measures that have been used to reduce the risks arising from the natural hazards. Explanation The hazard environment of Urban Valley means that some suburbs are susceptible to two or more related natural hazards that arise from a single trigger event. For example, Little Heritage is susceptible to fault rupture, liquefaction and tsunami arising from an earthquake on the Grand Fault. When the trigger event occurs, it is likely that people and properties situated in the areas that are susceptible to these natural hazards will experience all, or a combination of, these hazards. It is recognised that there is a relationship between the severity of the impact and the size of the hazard event; and that different size hazard events have different likelihoods. However, for the purposes of the district plan, the trigger event is considered to be a rupture of the Grande Fault, which has an annual likelihood of rupture of once every 880 years. When considering developments on properties that are susceptible to cascading natural hazards, a risk-based approach will be undertaken. This approach will ensure that the risk outcomes sought under this objective will be achieved (the formula for calculating cumulative risk is contained in Appendix 3) Objective - Account for vulnerable communities when considering natural hazards The vulnerability of a population shall be considered when determining whether it is appropriate for development to be located in an identified hazard zone. Policies a) Developments that could contain a number of vulnerable people (for example people who are young, old, unwell, mobility impaired or financially vulnerable) shall take into account this vulnerability when designing developments. b) The thresholds for what is considered to be an acceptable or tolerable level of risk shall be an order of magnitude higher, to account for this vulnerability. c) Developments designed for vulnerable people in cumulative and cascading natural hazard zones shall include engineering measures that reduce the risks from all of hazards that are in either the cumulative or cascading hazard zone as low as reasonably practicable. d) Any evacuation facilities provided to reduce the risk from a development for vulnerable people shall be designed to ensure that they are account for any physical or age related impairment. Explanation Not everyone is able to respond and recover from a natural hazard in the same way. There are sectors of the Urban Valley population that are more vulnerable to the consequences from natural hazard events. Factors that can contribute to this vulnerability include the deprivation of the community, and/or the age and health of the intended occupants. To ensure that vulnerable portions of the community are not located, or over represented, in hazard zones, the vulnerability of potential occupants of developments shall be considered GNS Science Miscellaneous Series 63 15

22 when assessing new developments. Developments that contain high numbers of vulnerable people (such as retirement villages, and early childhood centres) shall include engineering measures which reduce the risks from all of hazards as low as reasonably practicable. For example, for development in the cascading hazard zone, developments shall include engineering measures that reduce the risks from liquefaction, fault rupture and tsunami inundation. In recognition of the financial and social challenges that vulnerable communities can face, a higher risk threshold shall apply. This risk threshold shall be an order of magnitude higher for vulnerable developments than for non-vulnerable developments. The consent categories detailed in the chapter reflect this position. While it is recognised that this may discourage the development of these developments in certain portions of Urban Valley, it is considered that, on balance, the social benefits after a natural hazard event justifies this approach Objective - Protecting and enhancing natural features that reduce the consequences from natural hazards. Natural features that reduce the consequences from natural hazard events shall be retained, and if appropriate, restored when a development is being undertaken to enhance their hazard mitigation role. Policies a) Any natural features that have the potential to reduce consequences to a site from a natural hazard event shall be identified in any resource consent application. b) No development shall remove, degrade, or damage a natural feature in a manner which will result in an increase in the consequences from natural hazard events. c) Natural features on a site that reduce consequences from natural hazard events shall be retained, enhanced and protected as part of any new development. Explanation Natural features (for example dune systems, secondary overland flowpaths, wetlands, and vegetation cover) can reduce the consequences from natural hazard events by either acting as a barrier, providing storage capacity, or acting as a buffer between development and the hazard. Protection of these natural features is important. Many natural features are degraded due to human use of the environment. The protection and restoration of natural features that reduce the consequences from a natural hazard event shall be required as part of a resource consent application. The requirement to protect and restore these natural features can be achieved through the use of one or more of the following tools: Condition of resource consent, Via a consent notice on a subdivision; In lieu of the payment of a financial or development contribution; or Via an independent agreement with Council, this may include performance management criteria. 16 GNS Science Miscellaneous Series 63

23 3.3.7 Objective - Reducing the flood hazard from the Waitau and Urban Valley Rivers The existing levels of risk in the Waitau River and Urban Valley River hazards zones shall be reduced by incorporating mitigation measures into new development. Policies a) Development in the Waitau River catchment shall include an assessment of stormwater runoff. b) Developments shall include mitigation measures to ensure that the stormwater runoff does not exceed the existing runoff volumes for the site. c) Development shall reduce the risks from flood hazards and where reasonably practicable reduce the need for the response provisions of the Urban Valley Group Plan to be enacted in the event of a flood. d) The minimum floor levels of buildings in the Waitau River flood hazard zone shall be constructed above the 1:100year flood inundation depth. The Waitau River has a largely urbanised catchment and this is reflected by its response to high intensity rainfalls, with short, sharp flood peaks arriving a short time after the rainfall has fallen. This hydrological response from the Waitau River is typical of an urban water body with a large amount of impervious surfaces within the catchment, that directly discharge water into this river. This represents a greater flood hazard than a water body in a nonurbanised environment as more water is discharged into the river, more quickly, when compared to a natural environment. If the area of impervious surface in the Waitau River catchment was to increase, there is the potential for the associated flood hazard to increase. If the flood hazard was to increase, then the consequences and associated risks from flooding could be expected to increase. This policy therefore seeks to ensure that mitigation measures are incorporated into new developments in the Waitau River catchment that reduce the volume of water discharging into this waterbody. Such mitigation measures could include reducing the area of impervious surface on sites, incorporating swales and rain gardens into subdivisions, the installation of rainwater collection tanks, or rainwater detention tanks. It is expected that over time this policy will assist with reducing the sharpness, and height of the flood peak for the Waitau River. Unlike most seismic hazards, it is possible to forecast and provide warnings for floods. These warnings may trigger the response provisions of the Urban Valley Civil Defence and Emergency Management Group Plan, which includes evacuating people at risk from flooding on their properties. However, if there are a large number of properties to evacuate, or the warning of a flood is short (i.e. due to a severe thunderstorm forming over the region), the ability for Civil Defence to respond effectively will be reduced. It is therefore important that new development in the flood hazard zones of Urban Valley and Waitau Rivers recognise this risk and incorporate measures that will reduce the health and safety consequences and the level of response required by Civil Defence under the Emergency Management Group Plan. New development shall not increase the health and safety consequences from a flood on either Urban Valley or Waitau Rivers when compared to the existing development form of the site. GNS Science Miscellaneous Series 63 17

24 3.3.8 Objective - Integrated approach to reducing the risks from natural hazards To ensure an integrated legislative approach is taken to reduce the risks from natural hazards and to improve the readiness, response and recovery from an event. Policies a) Council shall make any information it holds on natural hazards publicly available and shall include this information on LIMs, including the hazard information identified in District Plans. b) The provisions of the CDEM Act 2002 shall be taken into account when assessing developments in a hazard zone, with a particular emphasis on ensuring that risk reduction outcomes are being achieved. c) Developments shall not substantially increase the need for readiness and response actions under the Urban Valley CDEM Group Plan during a natural hazard event. d) Emergency management staff shall be consulted as part of the process for considering new developments in the identified hazard zones. Explanation The Resource Management Act 1991 is one of several pieces of legislation that manages the consequences associated with natural hazard events. The objectives, policies and rules in this District Plan chapter are designed to integrate it with all of the pieces of legislation that manage natural hazards including: Local Government Act 2002; Civil Defence Emergency Management Act 2002; Building Act 2004; and Local Government Official Information Management Act The Civil Defence Emergency Management Act identifies the 4R s (reduction, readiness, response, and recovery) for the management of natural hazards. The Resource Management Act has been identified as being one of the primary tools to effectively achieve reduction. This is reinforced through the Urban Valley Emergency Management Group Plan, where the primary approach for achieving risk reduction is through the tools available under the Resource Management Act. To ensure that effective reduction of natural hazards is achieved, the Urban Valley Emergency Management Group Plan has been used to identify the primary natural hazards that affect the region. By reducing the risks from these natural hazards, it will allow for the readiness, response and recovery sections of the CDEM Group Plan to work more effectively. To assist the local population with their understanding of the natural hazards that affect Urban Valley, the Council will make publicly available any hazard information it holds. This includes providing a summary of all natural hazards that affect any given property (including any information identified in the District Plan), in any purchased Land Information Memorandum (LIM). The provision of this information will also assist with promoting readiness actions under the Urban Valley Emergency Management Group Plan. 18 GNS Science Miscellaneous Series 63