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Natural Hazard Risk Assessment - Ōtorohanga District

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Report: TR 2009/34

Author: G Ryan

About this report

This report provides an overview of natural hazards in the Ōtorohanga district as a basis for guiding and prioritising work activities by Ōtorohanga District Council (ODC) and Environment Waikato (EW) for 2009/10 and beyond.

It also provides a useful insight into the district’s natural hazards as part of the scheduled review of the Ōtorohanga District Plan.
Both agencies have responsibilities for the management of natural hazards in accordance to a complex set of statutory responsibilities, but primarily via the Resource Management Act 1991.

Known natural hazards in the Ōtorohanga district are identified and explained. Hazard scenarios are defined for each natural hazard and existing risk management controls are outlined. A preliminary (qualitative) risk analysis is then undertaken, and an evaluation of the risk from each natural hazard is made as a basis for prioritising risks.

River flooding hazards pose the greatest risk in terms of potential loss of human life, social disruption, economic cost and infrastructure damage. Coastal flooding has the second highest risk, and land instability has the third highest risk.

Read or download the report

Natural Hazard Risk Assessment - Ōtorohanga District (2mb)

Table of contents

  Executive summary 
1 Introduction 1
1.1 Purpose 1
1.2 Background 1
1.3 Statutory and legal framework 2
1.4 National drivers for hazard management 2
1.5 Key hazard planning considerations 2
2 Profile of Ōtorohanga District 4
2.1 General description 4
2.2 Physical setting 5
2.2.1 Geology 5
2.2.2 Climate 6
3 Natural hazards in the Ōtorohanga District 7
3.1 Introduction 7
3.2 Current and previous research 7
3.3 River flood hazards 8
3.4 Coastal hazards 8
3.5 Earthquake hazards 9
3.6 Tsunami hazards 11
3.7 Volcanic hazards 11
3.8 Landslides 13
3.9 Subsidence (karst) 13
3.10 Debris flows 14
4 Risk assessment 15
4.1 Introduction 15
4.2 Description of scenarios 15
4.3 Risk assessment methodology 16
4.4 Analysis and evaluation 16
4.5 Conclusion 17
4.6 Residual risks 18
5 Summary, discussion and recommendations 19
5.1 Summary of natural hazard risks 19
5.2 Discussion 19
5.3 Recommendations 19
6 References 21
7 Appendix 1: Statutory and legal framework 23
7.1 The Resource Management Act (RMA) 1991 23
7.1.1 Introduction 23
7.1.2 Long-term management strategies 23
7.1.3 Short-term management strategies 23
7.2 Resource management policy statements 23
7.2.1 Introduction 23
7.2.2 Regional Policy Statement (RPS) 24
7.2.3 Ōtorohanga District Plan 24
7.3 Other hazard management statutes 24
7.3.1 Introduction 24
7.3.2 Civil Defence Emergency Management (CDEM) Act 2002 24
7.3.3 Soil Conservation and Rivers Control Act 1941 25
7.3.4 Local Government Act 2002 25
7.3.5 Local Government Official Information and Meetings Act 1987 (LGOIMA) 25
7.3.6 Building Act 1991 25
7.3.7 Reserves Act 1977 26
8 Appendix 2: ODC/EW RMA functions 27
9 Appendix 3: RMA Section 330 28
9.1 Provisions and discussions of Section 330 of the RMA 1991 28
9.2 Further observations based on case law 28
10 Appendix 4: RPS & natural hazards 30
10.1 Policy One: Consistent Managment of Natural Hazards 30
11 Appendix 5: Other work 31
11.1 Hydraulic modeling 31
11.2 LIDAR surveys 31
11.3 River flood risk management 31
11.4 Categorisation of flood risk 31
12 Appendix 6: Key to Table 2 (risk analysis evaluation key) 33
12.1 Measure of likelihood 33
12.2 Measure of consequence of impact 33
12.3 Risk analysis matrix - level of risk 33
13 Appendix 7: Proposed Light Detection and Ranging (LIDAR) Survey Programme 34
13.1 Background 34
13.2 Benefits 34
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