Claire McKay is an Environment Canterbury councillor and also a resident of the Waimakariri district.
“I think it’s really important that we look after this area. We need to look at the impact of sea level rise and climate change here. We know that after the earthquakes the land subsided and that thelocation is very sensitive to high tides and floods. It’s a priority to get this flood protection in place to safeguard the area now and well into the future,” she said.
Councillor Grant Edge, also a Waimakariri District resident agrees.
“Part of the problem is the unreliability and erratic nature of future storm events. Hopefully over time people will appreciate that nature’s changing and it’s changing fast, and we all have to realise what the implications of that are.”
Kaiapoi – a history of flooding
Te Kōhaka-a-Kaikai-a-Waro or Kaiapoi pā was established by Tūrākautahi, the son of Tūāhuriri and one of the principal rangatira who led the Ngāi Tūāhuriri migration to Canterbury.
The pā was named Te Kōhaka-a-kaikai-a-waro — later shortened to Kaiapoi. It became a major Ngāi Tahu trading centre and stronghold. The streams, wetlands and forests of the area were mahinga kai (food and other resource-gathering) sites for the inhabitants of the Kaiapoi pā.
In 1849 Alfred Rhodes and four others sailed up to Kaiapoi and commenced the work of surveying the area. His explorations identified Kaiapoi as a feasible point of entry to North Canterbury, facilitating development of the fertile areas north of the Waimakariri. As the 1850s progressed Kaiapoi grew into an important trading point between the port and Lyttelton, facilitating transport of goods by bullock wagons to sheep stations as far north as Hurunui.
However, it was soon apparent why one of the Te Reo Māori meanings of Waimakariri is “river of cold rushing water”.
In the first three years of the Kaiapoi township’s existence in the 1850’s, it was beset with flooding of the Waimakariri River, enduring 16 devastating floods and spending almost all its revenues trying to keep the river at bay.
Farming began with the arrival of European settlers to the area from 1850 onwards, leading to permanent settlement on the rich plains. To enable and protect this settlement, drainage of the wetland areas and containment of the rivers was commenced.
Since 1859, engineers have been developing systems and structures to protect the Canterbury region from flooding of the Waimakariri River. The works developed by Environment Canterbury beginning in 1989 build on a legacy of pioneering engineers and flood protection works.
Building on early pioneering protection works
Major floods in 1865 and 1868 flooded Kaiapoi and Christchurch, with a resulting increase in efforts by engineers to contain the river. These works tended to focus on the southern (Christchurch) side of the river, creating understandable tensions between communities on the north and south sides.
The Waimakariri River Improvement Act was passed in 1922 and addressed these tensions by requiring flood and erosion protection along both sides of the river. The comprehensive Hays No. 2 Scheme; consisting of Waimakariri River straightening, stopbanking, and erosion control planting, was completed from the 1930’s to 50’s. Stopbanks were also constructed on the Eyre, Cust, Cam, and Kaiapoi Rivers to further reduce flood risk to Kaiapoi.
The North Canterbury Catchment Board took over scheme maintenance in 1946. Major floods in 1950, and the largest flood on record of 1957, caused breakouts threatening Christchurch and Kaiapoi. This resulted in the 1960 Scheme and upgrade over the period to the 1970s. The works included an increase in Waimakariri River stopbank flood capacity, erosion control measures to reduce riverbed aggradation, and rock bank erosion protection works at critical locations.
Environment Canterbury took over flood protection scheme maintenance from 1989 and although floods had been successfully contained since 1957, a hazards analysis highlighted the need for upgrades to protect the increased population and assets rapidly being established on the floodplain.
This discovery initiated the Waimakariri Flood Protection Project completed in 2019, a ten-year, $40 million infrastructure project that reduces the risk of flooding in Christchurch city and Waimakariri and Selwyn districts. It adds strength and resilience to the flood protection system already in place and significantly lowers the risk of break-out during major flood events.
The Waimakariri and Kaiapoi River stopbank protects Kaiapoi township and the surrounding area from flooding. They are part of the Waimakariri-Eyre-Cust flood protection scheme running the 70 kilometre length of the Waimakariri River from the foothills to the sea, providing wider flood protection for parts of Christchurch city, Selwyn district, and Waimakariri district.
In the 1960s, riverbank rock armour was installed to prevent erosion and stopbank breach on this very sharp bend.
Ian Heslop, who was the project lead for the Waimakariri Flood Protection Project, is also helming the project at McIntoshs bend, the popular fishing and recreational area located at the end of Ferry Road in Kaiapoi.
“This is a particularly difficult part of the river due to a sharp bend in an area where the river has also narrowed over the years causing a deep scour hole and increasing erosion vulnerability. This has resulted in an unacceptable level of risk of the river cutting through the riverbank and breaching the stopbank. It’s really important that we cut down that erosion and related flood risk,” he said.
“We need to strengthen the rock armouring along the riverbank and place some rock armouring along the stopbank to cut down the risk of the river breaking out. These new rock works will reduce erosion and flood risk to a level consistent with the remainder of the Waimakariri-Eyre-Cust flood protection system.”
Work is currently underway to strengthen a 400m length of stopbank and 700m length of riverbank using 19,000 tonnes of rocks from View Hill Quarry near Oxford.
Councillor John Sunckell (on the right) emphasised the importance of seizing this opportunity to make transformational change for the benefit of our iconic braided rivers.
One of the things that we’ve articulated through our Long-term Plan is the importance of opportunities for transformation, particularly within our braided rivers. This funding from the central government gives us the ability to not just upgrade our flood protection assets but also to look at biodiversity, our wetlands and flora and fauna. The transformation that we are looking for, and that the community are looking for, are really well served by this programme,” said Sunckell.