Regional flood summary: Ex-Tropical Cyclone Debbie (4-6 April), Tasman Low (11-13 April), and Ex-Tropical Cyclone Cook (13-14 April)
Report: TR 2017/20
Author: Heather Craig (with Sung Soo Koh, Jacob Williams, Dave Lovatt, & Doug Stewart)
About this report
Following a period of intense rainfall in parts of the Waikato region during March 2017, two ex-tropical cyclones and a low pressure system (Ex-Tropical Cyclone Debbie, Tasman low, and Ex-Tropical Cyclone Cook) made landfall in New Zealand on 4 April, 11 April, and 13 April.
The effects of these events were felt across the Waikato region with the Waihou River, Piako River and lower Waikato River systems being the worst affected.
These three April weather events caused disruption and damage to property and infrastructure across the Waikato Region with the Hauraki Plains and Lower Waikato the worst affected with several dwellings flooded and widespread road closures.
The purpose of this report is to summarise the rainfall events, provide rainfall and flood frequency relationships to inform additional scheme-specific performance reporting and capture the chronology of events detailed in Situation Reports issued during the events.
Read or download the report
| Contents | |
| 1 | Overview of Events |
| 2 | Comparison to previous significant flood events |
| 3 | Relevant WRC flood protection schemes |
| 4 | Regional Flood Response |
| 5 | Waikato Hydro Scheme and High Flow Management |
| 6 | Operations, observations and event impacts |
| 7 | Debriefings and lessons |
| 8 | Event magnitude summary |
| 9 | References |
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Appendix 1: Annual Exceedance Probabilities (AEP) for rainfall |
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Appendix 2: MetService watches/warnings, and WRC regional hazards advisories |
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Appendix 3: Annual Exceedance Probabilities (AEP) for instantaneous peak river flow |
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Appendix 4: River alarm levels |
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Appendix 5: Methodology memo - Flood frequency analyses for river levels and flows during |
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Appendix 6: Monthly river levels compared to March/April 2017 |
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Appendix 7: Road closures and disruption |
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