Ōtaki Gorge Road slips
Ōtaki Forks and Tararua Forest Park is a jewel in the Kāpiti crown and has been much missed as a place to get into nature and a visitor drawcard. The road remains closed to vehicles and pedestrians for safety reasons.
Vehicle access to Ōtaki Forks remains closed.
Walkers are not to cross at Blue Bluff, for their own safety.
The Department of Conservation has established an alternative public walking access to the Tararua Forest Park.
With winter 2023 upon us, we’d like to remind the community that the road access to Ōtaki Forks remains CLOSED as a result of major slips in 2020 and 2021.
There are two active slip areas in the Blue Bluff area include:
- the slow slip detected in September 2020, which has seen the road slump towards the river and caused the original closure
- a second significant slip 100 metres further towards Ōtaki Forks, which has completely covered the road; this began during the heavy rain event of 6–8 December 2021
- the wet winter of 2022 sparked further movement in the slip area.
Since October 2022, plans to open a walking track over the Ōtaki Gorge Rd slips blocking access to Ōtaki Forks and the Tararua Forest Park have been on hold, pending further geotechnical and other expert assessment. While a walking track has been built over the slips, the incredibly wet winter of 2022 caused further movement and instability. This includes new slips in other areas, a risk of further washout, and the possibility of rock fall.
Council continues to take a cautious approach in the interests of public safety and keep the new walking track closed until we can be sure the area is stable enough to open.
We know this is frustrating for many who had hoped to easily return to the Forks area and wider Forest Park, but we must put public safety at the forefront of decision-making.
Live monitoring equipment has been installed to provide better information about movement and activity, and sensors are showing there has been some slipping caused by the wet winter.
We are seeking further advice from geotechnical engineers and track experts.
DOC emergency walking track
The DOC-built emergency walking track is open and provides access to the Tararua Forest Park. Note this is a challenging walk requiring good fitness and tramping experience.
We are developing longer term options for Ōtaki Gorge Road.
Work to date
Research work on the earlier slow slip was ongoing throughout 2021. Starting in April 2021 we began looking at how we might be able to open road access to Ōtaki Forks, moving from monitoring the slip to active investigation on the site. This involved specialised geotechnical work including test pits, core holes, and installing equipment to monitor groundwater levels.
Geotechnical investigation showed the slip zone runs deep into two types of material and that wet periods and heavy rain are key factors that accelerate movement. By the end of May, our investigation had found several metres of river gravels deposited when the river was much higher many thousands of years ago, with fractured greywacke bedrock underneath that.
This information would inform the development of options and a design for how the road could be reopened.
The wet period in June 2021 reactivated the slow slip and we observed significant deformation of the road and the slip face slump into the river.
In the latter part of 2021 the road had stabilised enough to reopen part of it for a walking and cycling track along the wall side of the road. Site works had progressed prior to the recent major slip.
This would provide much better access for those wishing to make the 4km journey to the Forks by foot or bike. Re-opening the road to vehicles was still not an option.
The slip triggered by rain event of 6 to 8 December 2021 has forced us to cancel that plan.
About Blue Bluff
The Blue Bluff section of the Ōtaki Gorge Road is an a area that becomes active during wet weather.
The road is on a steep embankment above the Ōtaki River, which is naturally degrading the river bed and embankments. The Ōtaki Forks area receives intensive rainfall further adding to the challenges of this road.
The road has been closed to walkers and vehicles since September 2020, when heavy rain caused new damage to the bank. The road had been closed for seven months in 2016 due to slip activity at the same location.
Pictures of the slip
- Improving access to Ōtaki Forks (30 June 2022)
- Investigative work to restore access to Ōtaki Forks kicks off (20 April 2021)
- Ōtaki Gorge Road to remain closed at Blue Bluff for summer peak (3 Nov 2020)
- New damage at Blue Bluff, Ōtaki Gorge Road causing concern (25 Sept 2020)
- Minor slip cleared at Ōtaki Gorge Road (24 August 2016)
- Ōtaki Gorge Road reopens after seven-month closure (15 July 2016)
- Council urges people to stay clear of Blue Bluff slip (22 Feb 2016)
- Fresh slip at Blue Bluff, Ōtaki Gorge Road (20 Feb 2016)