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Clarence-Waiau Toa River

Over 200km long, the Clarence River – Waiau-toa (Māori) is the 7th longest river in New Zealand (click for interactive catchment map). It originates in the northern part of the Southern Alps, St James Range and Spencer Mountains, and Lake Tennyson. From here it flows in a south-easterly direction through the Clarence Valley and  Molesworth Station. 

Just north of Hanmer Springs, the Clarence River angles sharply northwest, flowing between the inland and seaward Kaikoura Ranges before turning south where it reaches the Pacific Ocean about 30km north of Kaikoura near Clarence township. 

In terms of management, the Clarence/Waiau-toa River catchment is split between the Kaikoura Zone and Marlborough District Council. The Marlborough District Council is able to have an “ex officio” observer to the Zone Committee and both parties are committed to working together on areas of common interest.

Clarence River, Clarence Valley
Clarence River, Clarence Valley

Biodiversity & Cultural Significance

Clarence River mouth. Note the classic braided ‘delta’ fan shape built from sediment and gravels deposited over time.
Clarence River mouth. Note the classic braided ‘delta’ fan shape built from sediment and gravels deposited over time.

The upper reaches of the river is an important breeding area for the black-fronted tern.

Extract from the Kaikoura Zone Implementation Programme: ‘Weed and pest control is critical to maintain biodiversity and the natural values of the river.

‘The main weed challenges on the Clarence/Waiau-toa river is willow, broom and gorse. The lower Clarence/Waiau-toa River bed and adjacent area does not have gorse or broom. The upper catchment, however, does have large areas of gorse and broom. The river is a conduit for weed seeds and active wellresourced control in the upper catchment is critical if the lower river is to remain gorse and broom free.

There is currently some co-ordination of managing gorse and broom throughout the length of the river between Environment Canterbury, DOC and Land Information New Zealand (LINZ). East Coast Community Organisation (ECCO)( the local landcare group) also plays a focal role in coordinating river-bed weed management in the lower Clarence/Waiau-toa, and informally this extends to the middle Clarence/Waiau-toa.However, the Zone Committee believes that there is scope for improving the management of river bed weeds through a more integrated and whole of catchment approach that would also ensure that current funding is spent effectively. It is important that all parties involved in managing weeds on the river are engaged in the discussion and accordingly ECCO should be an integral part of this process. The Zone Committee also believes a weed management strategy needs to be developed for the Clarence/ Waiau-toa catchment to provide long-term control.

‘The Waiau-toa holds immense cultural, spiritual and historical importance for Ngāti Kuri and figures prominently in tribal history. The Waiau-toa is considered to have the status of a parent of many other rivers in the region, with an impact on the Waiau-toa having an impact on those rivers that are linked to it through whakapapa. It is also a known Ara Tawhito (ancient trail), a pounamu trail, linking the Kaikoura coast with the Lewis Pass and on to the West Coast. Continued access through this area is therefore important to Ngāti Kuri. The protection of remnant wetlands in the catchment is also of particular concern to Ngāti Kuri.’

Important Bird Areas on the Clarence/Acheron/Saxton Rivers: links to 7-page PDF file that includes maps, habitat types, and threats relevant to this river. This document was extracted from Forest & Bird’s 177-page 20Mb file on all rivers, lakes, and coastal areas.

Important Bird Areas on the Clarence River Mouth: ditto – 5-page PDF.

Conservation activities including bird counts

Water flow

Trapping layout at Bush Gully around the colony of black-billed gulls. The traps were set 1km up and downstream, then in a 500m radius around colony.
Trapping layout at Bush Gully around the colony of black-billed gulls. The traps were set 1km up and downstream, then in a 500m radius around colony.

2022 seminar keynote address: The shifting frontlines of tarapirohe/black-fronted tern conservation (also available as a PDF) 

Impacts from the Kaikoura earthquake sequence

The 7.8 (Mw) Kaikoura earthquake sequence November 14, 2016 resulted in large, landscape-scale changes to sections of the the river catchment. Parts of the river were blocked or changed course due to faults and landslips, resulting in flooding and new lakes forming behind (often unstable) natural dams. These are a selection of videos taken from the air showing some aspects of those (in many cases permanent) changes to the river. The long term impacts on flora and fauna is unknown.

Fault scarp and flooding at the Clarence Valley Road Bridge (15 Nov 2016)
Breached landslide dam in the Clarence River (15 Nov 2016)

References & Research