Go west!

27/06/2013 § 2 Comments

The local news over the last week has been the storm in Wellington. It was the biggest in a while, by some measures bigger than the infamous 1968 storm. It took out the rail link between the central city and the Hutt Valley, leading to long waiting times and difficult commutes. That has now been fixed and the trains are running this morning.

Here’s the thing — it’s going to happen again. The rail line is at the water’s edge in the harbour, as this picture from stuff.co.nz makes clear:

washout

That water right there? Only going to get higher. Sea level rise is projected to raise the water level over the next 100 years and beyond. This Niwa report (pdf) provides a lot of detail, but the basic idea is that we’re looking at 1.5m to 2.0m rise in the average sea level over the next century. Of course, that’s the average. Storm surges will push the water higher at random intervals.

This is an interesting map, from the 2011 regional transport plan (pdf) (Figure 8, cropped). It is essentially a ‘heat map’ of access to public transportation, red being the best access, then orange, yellow and blue. You can see the narrow rail corridor linking the central city with Lower Hutt, the black line on the northwest edge of the harbour. That’s what washed out.

WLGtrans

The rail line is on the water because the hills are hard up against the harbour at that point. The route was actually produced by the 1855 earthquake:

The uplift created a new fringe of beach and rock platforms along the Wellington coast…. The newly exposed strip of shoreline between Wellington and the Hutt Valley offered a safe road and railway route – parts of the coastal road had previously been impassable at high tide.

All of this comes at a time when the council has just decided about future transport infrastructure in order to improve transit times between Kilbirnie and the central rail station. The big news was that the mayor backed away from light rail to support instead a bus-based option:

“While light rail is attractive, bus rapid transit may be a more immediate and pragmatic step and I want significant progress well before 2021,” she said.

Here’s my problem: those areas of the map are already red. They are already well serviced by the existing network. Other red-orange areas of the map are the suburbs north of the central city, which have rail links. The link to the Hutt is obviously fragile and only going to get worse.

I’d like to see the transport network improve access in poorly-served areas. All that yellow and blue land south and west of the centre city could be opened up, reducing the cost of housing and improving its quality while reducing the fragility of the transport network. Yes, I realise that will cost money and that topography isn’t in our favour. But we are planning to spend hundreds of millions of dollars to improve public transport to people who are already well serviced. Is that the best use of the money?

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§ 2 Responses to Go west!

  • Jez says:

    I think the next IPCC report is going to come out with some stronger upper bounds on how rapidly sea levels will rise. Much of the discussion I’ve been hearing from climate scientists has talked about rises of more than a metre by 2100 being pretty unlikely, or at least less likely than thought a few years back.

    For a transport corridor like SH2/HVL, that means raising the levels by 10 centimetres per decade. Given how often roads are resurfaced, it’s not a big extra cost just simply grind less off before relaying the surface. Train lines, I’ll admit, do need a more deliberate approach to raising them up, but the benefit/cost ratio justifies fixing them.

    Other coast roads with less traffic, however…

    • That’s good news, both that the research is coming up with better upper bounds, and that the SLR might not be as high. Obviously, that affects any cost-benefit analysis.

      I like what you’ve done here — you’ve asked what’s really the problem (we need to keep roads out of the water) and what’s a cost-effective solution (build them up over time).

      With that in mind, is the Kilbirnie-rail station plan a solution in search of a problem?

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