Cyclone impacted catchments tracked
From local democracy reporter Brendon McMahon:
Landslides high above State Highway 67 north of Westport in a stream catchment straddling an active fault-line is worrying the West Coast Regional Council.
An internal engineering staff report has highlighted the deterioration of vegetation on slopes at Barrytown and parts of Buller from Cyclone Ita in 2014, and delves into the progressive erosion in the Lake Stream catchment, 10km northeast of Westport township.
The cyclone caused massive damage throughout the entire West Coast, flattening swathes of native forest and vegetation, particularly in river valleys.
In Buller, the Lake Stream catchment on Mt Rochfort had already split into three channels by the time of the heavy storm this February, but the erosion has now escalated, regional council engineer Paulette Birchfield said.
"Multiple landslides" had left a huge volume of slip material sitting high up in the catchment, about 1 kilometres above the highway.
When the slip material did eventually move it could radically change the stream's direction, with significant potential to spill on to the road at the bottom of the slope, Birchfield said in her report.
The majority of the slips in Lake Stream were in the upper catchment, diverting the flow across a fan. In future heavy rain events the high slip material was likely to mean the stream would "take any number of other flow paths".
Birchfield said the possibility of mechanically diverting the flow and excavating the original Lake Stream channel would be difficult. Steep topography and thick vegetation made both foot and access for machinery challenging.
A large-scale landslide did occur in the catchment in at least 2015, a year after Cyclone Ita, and this had been supplying increased sediment and debris to the Lake Stream channel.
In normal conditions the stream flow would not have sufficient energy to transport additional slip material and the channel would slowly evolve in response.
However, an earlier heavy rainfall event in early May 2020 was probably large enough to move significant volumes of sediment and debris, causing Lake Stream to tear away from its original channel, breaking out in several places.
A 1997 thesis noted that until the downstream channel width and depth was increased to the new flow regime, floodwaters would continue to break out of the channels and drains, causing flooding and sedimentation of farmland and damage to property.
PICTURES: West Coast Regional Council
1: Lake Stream catchment, north-east of Westport.
2: Approximate location of the diversion site in Lake Stream.
Poll: Should we be giving the green light to new mining projects? 💰🌲
The Environmental Protection Authority announced this week that a proposed mine in Central Otago (near Cromwell) is about to enter its fast-track assessment process. A final decision could come within six months, and if it’s approved, construction might start as early as mid-2026.
We want to know: Should mining projects like this move ahead?
Keen to dig deeper? Mike White has the scoop.
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53.4% Yes
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46.6% No
A riddle to start the festive season 🌲🎁🌟
I'm a fruit. If you take away my first letter, I'm a crime. If you take away my first two letters, I'm an animal. If you take away my first and last letter, I'm a form of music. What am I?
Do you think you know the answer? Simply 'Like' this post if you know the answer and the big reveal will be posted in the comments at 2pm on the day!
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Head here and hover on the Following button on the top right of the page (and it will show Unfollow) and then click it. If it is giving you the option to Follow, then you've successfully unfollowed the Riddles page.
‘Tis the season to not get scammed ...
As Christmas gift shopping moves increasingly online, scammers are ramping up their activity across the country.
Dunedin’s Investigation Support Unit is seeing more and more people fall victim to scams and other fraudulent activity, particularly on Facebook Marketplace.
There are a few ways to avoid the scams and keep yourself safe doing online trades this holiday season, says Southern District Service Delivery Manager Senior Sergeant Dalton.
🔒 “A good first step when looking to purchase something on Marketplace is to check when the seller’s Facebook profile was created. If it’s very recent, there is a higher risk that they have just created this account for a one-off fake item.”
🔒 Another important step is to make sure the seller’s profile name and bank account name match up. “We’re seeing a lot of scammers claiming their bank account name is different because it belongs to their partner or family member - that’s a huge red flag."
🔒 “When you’re selling, never trust a screenshot anyone sends you showing that payment has been made. Check your own bank account to make sure a payment has gone through."
🔒 “Quite frankly, it’s best for all parties to agree to pay, or be paid, for items in cash and in-person. Ideally in a public place with CCTV coverage."
🔒 "If you’re buying a car, check Carjam.co.nz to see if it’s stolen or if there’s money owed on it.”
A reminder: Suspicious activity can be reported on 105
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