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An Overview of Natural Hazards in the Hauraki District

TR 2006/16

Report: TR06/16

Author: Adam Munro


The purpose of this report is to provide an overview of natural hazards in the Hauraki district as a basis for guiding and prioritising work activities by Hauraki District Council and Environment Waikato for 2006/07 and beyond. This report also provides a useful insight into the district's natural hazards as part of the scheduled review of the Hauraki 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 Hauraki 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. This approach is very similar to the hazard assessment that was carried out for the Thames-Coromandel district as part of the Thames Coast Flood Risk Mitigation project.

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 earthquakes have the third highest risk. The report also identifies various factors/considerations that are likely to affect natural hazard planning such as climate change, sea level rise, and tectonic deformation.

An Overview of Natural Hazards in the Hauraki District [PDF, 718 KB]

Executive summary v
1 Introduction 1
1.1 Purpose 1
1.2 Scope of report 1
1.3 Background 2
1.4 Statutory and legal framework 2
1.5 National drivers for hazard management 2
1.6 Key hazard planning considerations for HDC 3
2 Profile of the district 4
2.1 Physical setting 4
2.1.1 Geology 4
2.1.2 Climate 6
2.1.3 Facts and figures 7
3 Natural hazards in the Hauraki district 8
3.1 Current and previous research 8
3.2 Flood hazards 9
3.2.1 Background 9
3.2.2 River and catchment management 10
3.2.3 The Waihou Valley Scheme 10
3.2.4 The Piako River Scheme 13
3.2.5 Potential effects of natural hazards on protection schemes 15
3.2.6 Other work 16
3.2.7 Hauraki district flood hazards - summary 16
3.3 Coastal erosion and flooding hazards 17
3.3.1 Whiritoa 17
3.3.2 Hauraki Plains 18
3.4 Severe storm hazards 18
3.5 Earthquake hazards 18
3.5.1 The Kerepehi Fault 19
3.6 Tsunami hazards 21
3.6.1 Current research 22
3.7 Volcanic hazards 22
3.8 Debris flow hazards 24
4 Risk assessment 25
4.1 Hauraki hazards - risk description/scenarios 25
4.2 Residual risks 25
4.3 Hauraki hazards - risk analysis/evaluation overview 26
4.4 Existing risk management controls 26
4.5 Risk analysis/evaluation 26
4.6 Conclusion 26
5 Summary and conclusions 29
5.1 Summary of natural hazard risks 29
5.1.1 Relationship to river and catchment management 29
5.1.2 General hazard and risk considerations 30
5.1.3 Conclusion 30
Appendix 1: Statutory and legal framework 31
Appendix 2: HDC/EW RMA functions 36
Appendix 3: RMA Section 330 37
Appendix 4: RPS and natural hazards 40
Appendix 5: Other work 41
Appendix 6: Key to Table 4 44
Appendix 7: Proposed Light Detection and Ranging (LIDAR) Survey Programme 45