Report: TR 2017/21
Authors: Heather Craig
The March 2017 rainfall event (collequially known as the Tasman Tempest) comprised of a series of heavy rainfall bands with the two most significant occurring overnight on 7/8 March and 10/11 March.
The size of the event varied across the affected areas, the Lower Waikato, Waihou/Piako, and Coromandel areas (or WRC catchment zones) were impacted with maximum river flow event frequencies of 20-10% (Mangatawhiri), 10-5% (Kauaeranga), and <2% AEP (Waiwawa) respectively.
A significant amount of disruption to infrastructure was a result of this event. Roading, power networks and water supplies were impacted and a number of communities were isolated after significant overnight rainfall.
The purpose of this report is to provide a summary of rainfall events, and the observed river flows and water levels that resulted as part of the March rainfall event.
This report also aims to describe the response of Waikato Regional Council (WRC) to these events, provide the rainfall and flood frequency relationships to inform scheme-specific performance reporting and capture the chronology of events detailed in the Situation Reports issued by WRC offices during the events.
|1||Overview of Event|
|2||Relevant WRC flood protection schemes|
|3||Regional Flood Response|
|4||Operations Observations and Event Impacts|
|5||Debriefings and lessons|
|Appendix 1: MetService warnings/watches and WRC regional hazard advisories|
|Appendix 2: Rainfall and river flow frequency calculation methodology|