XC Dawlish cancellations now beyond a joke!

[whole diary]

[Dispatch Box]

In advance? Since the Dawlish closure, I think.

Lines are open now, are they?.

[broadgage]

How many years have these services been suspended in advance for?
Surely the weather conditions have been the same for years and years, just seems people are being overly cautious more often

I am not convinced that the weather conditions have been the same for years.
The sea level has increased, only marginally I know, but still an increase.
Wind speeds may also have increased.

Add this to an abundance of caution, and poorly designed rolling stock, and it is not surprising that weather related cancellations are increasing.

[Celestial]

The sea level has gone up by around 60mm since 2002 which I think is when the Voyagers were introduced.  How much difference that makes at the sea wall I don't know, but I suppose there must be some.  How many more years have the Voyagers got I wonder, and how much will the sea level increase in that time?

[Oxonhutch]

Having a keen interest in these things, I can't conclude that there has been such a dramatic rise in sea level in just 16 years. In support I would direct observers to this data-rich site from the NTSLF at Newlyn

[broadgage]

Having a keen interest in these things, I can't conclude that there has been such a dramatic rise in sea level in just 16 years. In support I would direct observers to this data-rich site from the NTSLF at Newlyn

I agree, see levels are rising but not that fast. Very roughly 1mm a year has been the average for the last century or so.
Many experts are however forecasting a faster increase in years to come as polar ice melts, and as ocean water becomes warmer and therefore expands.

[Celestial]

So I used
https://climate.nasa.gov/vital-signs/sea-level/
which shows an increase from 26 in 2002 to 87 now, and also says levels are increasing at 3.2mm a year.

Maybe I've not understood the page, in which case happy to be corrected. That will teach me to post about things I don't really know about.  What do they say about a little knowledge?

[ellendune]

So I used
https://climate.nasa.gov/vital-signs/sea-level/
which shows an increase from 26 in 2002 to 87 now, and also says levels are increasing at 3.2mm a year.

Maybe I've not understood the page, in which case happy to be corrected. That will teach me to post about things I don't really know about.  What do they say about a little knowledge?

I think the difference is that one is a global average and the other is measurements at Newlyn. 

[Oxonhutch]

I think the difference is that one is a global average and the other is measurements at Newlyn. 

To quote from the NTSLF site:-

This average long term trend is estimated as 1.4 ± 0.2 mm yr−1 which is slightly lower than the 1.7 mm yr−1 consensus value for global sea level change over a similar period

The difference (0.3mm/yr) is most likely the ongoing isostatic rebound from unloading the mass of the Ice Age glaciers > 10,000 years ago;

and as ocean water becomes warmer and therefore expands.

For the most common liquids, water has one of the lowest coefficients of thermal expansion, so that will not be a major contributor. Other geological processes have a far greater effect.

[grahame]

Maybe I've not understood the page, in which case happy to be corrected. That will teach me to post about things I don't really know about.  What do they say about a little knowledge?

A little knowledge is step along the way from no knowledge to a lot of knowledge, isn't it?    

This forum is founded on those who don't know or who aren't sure about something feeling they can ask and being filled in ... and at the same time helping build up a resource for all those others who have wondered the same thing.  Keep posting  

[stuving]

I think the difference is that one is a global average and the other is measurements at Newlyn. 

To quote from the NTSLF site:-

This average long term trend is estimated as 1.4 ± 0.2 mm yr−1 which is slightly lower than the 1.7 mm yr−1 consensus value for global sea level change over a similar period

The difference (0.3mm/yr) is most likely the ongoing isostatic rebound from unloading the mass of the Ice Age glaciers > 10,000 years ago;

and as ocean water becomes warmer and therefore expands.

For the most common liquids, water has one of the lowest coefficients of thermal expansion, so that will not be a major contributor. Other geological processes have a far greater effect.

The south of England is falling (due to the rotational effect of isostatic rebound - the north of Scotland is rising and by more) by rather more than that, with a figure quoted here of 1-2 mm/yr. That figure depends on how you measure it, though. I have a vague recollection that the same is true of "absolute" sea level, with the satellite measurements not agreeing with local ones.

In any case, from the point of view of what happens to trains at Dawlish, mean sea level hardly matters - it's how high high tide gets that matters. The NTSLF site does estimate that too:

The long term trend in 99 and 1 percentile is 2.2 and 1.8 mm yr−1, compared to the trend of 2.1 mm yr−1 in median sea level. Trends for the extremes are more difficult to calculate because of the greater variability in their records. Those for high and low extreme levels are 2.2 and 1.3mm yr−1. The small gradual greater increase in high waters over low waters is considered to be a consequence of increasing local tidal amplitudes...

So it's not as simple as you'd think (even if you don't think it is simple).

[ellendune]

In any case, from the point of view of what happens to trains at Dawlish, mean sea level hardly matters - it's how high high tide gets that matters. The NTSLF site does estimate that too:

The long term trend in 99 and 1 percentile is 2.2 and 1.8 mm yr−1, compared to the trend of 2.1 mm yr−1 in median sea level. Trends for the extremes are more difficult to calculate because of the greater variability in their records. Those for high and low extreme levels are 2.2 and 1.3mm yr−1. The small gradual greater increase in high waters over low waters is considered to be a consequence of increasing local tidal amplitudes...

So it's not as simple as you'd think (even if you don't think it is simple).

Does that include the consideration of storm surges?  And wave heights?

If it does then the average is not meaningful as they happen infrequently so the true amount would be hidden. 

If it does not then they need to be taken into account.

The problem then measured not by an average but a number of times in a fixed period a critical amount is exceeded? 

[Celestial]

Maybe I've not understood the page, in which case happy to be corrected. That will teach me to post about things I don't really know about.  What do they say about a little knowledge?

A little knowledge is step along the way from no knowledge to a lot of knowledge, isn't it?    

This forum is founded on those who don't know or who aren't sure about something feeling they can ask and being filled in ... and at the same time helping build up a resource for all those others who have wondered the same thing.  Keep posting  

Thank you for the encouragement grahame.

Though having seen the later posts, I think I shall nod wisely as if I understand, step back from the discussion, and remember to check tide times and heights and the long range weather forecast before booking my next trip to the south west.

[grahame]

Maybe I've not understood the page, in which case happy to be corrected. That will teach me to post about things I don't really know about.  What do they say about a little knowledge?

A little knowledge is step along the way from no knowledge to a lot of knowledge, isn't it?    

This forum is founded on those who don't know or who aren't sure about something feeling they can ask and being filled in ... and at the same time helping build up a resource for all those others who have wondered the same thing.  Keep posting  

Thank you for the encouragement grahame.

Though having seen the later posts, I think I shall nod wisely as if I understand, step back from the discussion, and remember to check tide times and heights and the long range weather forecast before booking my next trip to the south west.

It is reminding me rather of the thread that talked about the pressures put on the track and trains where the line went from level to a rising gradient, and the flexibility built in where that was a change to an artificial structure such as a flyover.  I am just reading on this one too ... happy to chip in with questions, but in "read mostly" mode!

[rower40]

They can insist all they like but unless they stump up the cash Voyagers will continue to operate XC^▸ (Cross Country Trains (franchise)) for quite a few more years yet sadly.

How many HSTs^▸ (High Speed Train) do Cross Country have?   Could they have a few more from cascade leftovers to help relieve congestion on their voyagers?   And in stormy times split their route at either Exeter or Bristol Temple Meads such that the HSTs run a sea wall shuttle to Plymouth and beyond, cross platform change at those times for through passengers?

So your thinking all voyagers from Edinbugh or Glasgow central to Plymouth or Penzance all Terminate at BTM^▸ (Bristol Temple Meads (strictly, it should be BRI)), Then Bristol to the west country to save long delays.

Also to prevent water lashing over railway at Dawlish could NR^» (Network Rail - home page) Put some sort of glass on the wall to keep back waves. This would be a permanent solution to the problem, and cheaper than diverting the lines.

All trains would terminate on platform 5, and ones from Devon on platform 6, then passengers would then just need to go to opposite end of the platform to continue their onward journey. Fine by me.

Combination of both of these ideas...

On Stormy days, use the surplus HSTs as a mobile wall that can be dragged out of sidings at Exeter Riverside and parked on the Down Main.  Then use the Up Main bidirectionally; Voyagers will be protected from the salt water by the HST Glass Wall.

[IndustryInsider]

Could you not leave it parked up there all year round just in case? In the summer the buffet could be used to sell refreshments to those walking along the sea wall.