Tuesday, 3 May 2016

Further damage alleged to Whareratas section of Gisborne Line

An interesting letter was recently published in the Gisborne Herald by one Merv Goodley of Mahia concerning the likelihood of further damage to the rail line between Wairoa and Gisborne. . 

Here are some aerial photos showing some of the damaged areas of the line.

At upper left is the Wharekakaho Stream, a location where a blocked culvert was identified after the March 2012 weather bomb event where floodwaters had partly undercut the embankment, track however was left intact. Further south we can see evidence of significant water flows and erosion of the track sides.

This is the north end of Beach Loop and we can see a lot of erosion around the track both above and below.

This area just south of Beach Loop has been on the move for years but is looking pretty serious at this time.

Just to the north of the demolished Tunnel 24. The tunnel was removed in the mid 1950s because of a landslide in the hill it was driven through.

This photo joins the one above showing significant erosion all along this section of the line.

Undercutting of the embankment at Wharerata Walkway station.

Significant embankment erosion at 349 km. My guess is this is the location referred to where railway wagons were used to reinforce the track which have now collapsed into the river.

Hillside above the track collapsed about 5-6 years ago at this location between Tunnel 16 and Bridge 265. The line was operating at the time and the slip took about a month to clear.

Even in 2011 it was clear there was a slip developing at the north end of the Kopuawhara Viaduct. It has continued to grow since then.

Undercutting of embankment into the river just south of 347 km.

Blacks Beach, the site of the 1957 slip referred to in the letter. The road is being undercut by the sea due to erosion which also threatens the railway alongside.

The significant parts of the letter include the following quotes

I was lucky enough to go into the Kopuawhara headwaters in a four-wheel-drive vehicle from JNL’s Wharerata headquarters, and saw a lot more blowouts that have occurred since the intial damage in March 2012. At one spot, 10 or so years ago, the then rail operator packed one blowout with railway carriages to hold the line in place. Those carriages are now laying some 40 metres below the track in the river bed. I would say to fix the rail line in the Wharerata area alone, for the long term, would cost $60 million to $80m. One area would need a viaduct system to solve the unstable land, two years to complete just fixing the damage. Look at Black’s Beach slip August 12, 1957, 19 bulldozers to clear 87m track one month day and night. Any part of Black’s Beach could slip under the line into the sea as it is so unstable there. The situation is the same at Beach Loop, Paratu, Kopuawhara Valley, Waikokopu. Is it true that the Mohaka Viaduct needs over $2m spent on it for painting alone? Then there are all the other bridges and crossings etc.