Sh1 damage from Cyclone

20 March 2019 Chloe Brigden

This time last year ex-tropical cyclones Fehi and Gita caused over $81 million dollars of destruction during their six-week siege of New Zealand’s west coast.

The fury of Fehi and Gita forced the West Coast, Nelson and Tasman regions into a state of emergency; with many communities needing to evacuate their homes due to severe storms, flooding and contamination.

Source: Worldwide Breaking News


  • Dunedin City Council reported more than 108mm of rainfall in Dunedin
  • Up to 800 properties were vulnerable to flooding in the Dunedin area
  • Insurance Council of New Zealand (ICNZ) reported insurance claims of up to $45.9m


  • The Met Office recorded a peak gust of 144km/h on Stephens Island
  •  On Port Taharoa Buoy, waves were recorded to reach 8.3m (with a rogue wave of 15m recorded)
  • Rainfall exceeded 100mm in 15 different locations across NZ
  • Thousands of Kiwis were left without power in Taranaki
  • Roads were reported blocked and unsafe due to landslides
  • ICNZ reported insurance claims of up to $35.6m 

Alongside the destruction caused to the primary lifelines; clean water, food and shelter – was the damage caused to secondary transport networks. 

SH1 (North of Wellington), and SH6 on the South Island (west coast at Punakaiki) received the brunt of Fehi and Gita’s wrath. Both saw major carriageway and structure damage – so intense that underground services were exposed. 

The aftermath of Fehi and Gita called for an urgent response. In collaboration with Roading Infrastructure Management Support (RIMS), the Institute of Public Works Engineering Australasia (IPWEA), Infrastructure Decision Support (IDS), the New Zealand Utilities Advisory Group Inc. and The Road Efficiency Group (REG) – WSP Opus delivered a scope of services, from technical advice and support to the design of the urgent repair work needed for the highway protection structures for both SH1 and SH6.

Matt Balkham, WSP Opus Work Group Manager for Water Resources was the technical lead for the work carried out by the team. Matt’s expertise in erosion and flood-risk management allowed for the appropriate and practised assessment of the damages made – and solutions needed – for the two networks.

WSP Opus Sh1
“To ensure that the repairs met the current and future needs of the network entailed discussions on levels of services with the NZTA and the key stakeholders” Say’s Matt.

“As the repair design progressed, the dialogue turned to articulating residual risk and planning for future events. This also helped to inform investment decisions.”

A series of calculation outputs helped to facilitate the meaningful conversations mentioned above; about how a structure is intended to perform and the nature of residual risks.”

Scope of services:

  • Maintenance activities such as seawall inspection, rearrangement of the seawall rock, vegetation management, upper slope treatment and toe and crest repair.
  • Design work including, redesign of the damaged assets, new design for access arrangements, design for crest height, toe detail and overtopping rates.

Community and driver safety was a fundamental priority and overriding theme throughout the entire project life-cycle. In addition to the tangible, infrastructural solutions that WSP Opus and partners provided – proactive on-site safety-management measurements were also required.

This included organising road closures, issuing appropriate safety warnings to the community, aquaplaning and drainage services, debris removal, plus, safeguarding the infrastructure of natural elements such as the nearing cavern and foreshore.

Copy of Copy of Copy of Copy of WSP Opus Revolutionary Wastewater Sludge Treatment
Matt will be referencing the above project at this week's Roading Infrastructure Management Support (RIMS) Conference. His presentation, Levels of Service for the Repair of Cyclone Damaged Coastal Revetments, will discuss the detailed work, levels of services and design philosophy. 

Additional WSP Opus Speakers:

The Use of UAV's to assist Road Corridor Management 
David Stewart, Principal Geotechnical Engineer, WSP Opus

21st March 
9:10 am 


Communicating the Investment Story - IDS Dashboard Development 
Tim Cross, Business Systems Analyst, WSP Opus 

21st March 
10:50 am


How strong is your bridge? Optimising New Zealand’s longest road bridge
Jeremy Waldin, Technical Principal - Bridge Asset Management
21st March 


Transforming footpath data to dollars – Lessons learned
Greg Marrow, Group Manager - Asset Management
21st March