Carmont derailment - report today

[keefer]

Just to mention how intense the weather event was, which led to the landslip. This was a severe, slow moving thunderstorm(s) which (where I am, in Kirkcaldy Fife) lasted from around 8pm to 5am the next morning.

The only time i can think of one lasting so long and being so intense was probably in August 1975. The lightning was constantly flickering, with many closer strikes and seemingly explosive thunder, and of course torrential rain.

The site at Carmont had this storm for a fraction of the time but the deluge of rain in that period was enough to cause the problems - I shudder to think what the line would've looked like if it had storms for the full duration experienced further south. I expect the line would've been impassable first thing and to a much greater extent - which may mean the accident wouldn't have happened (no trains running) but the line would've been closed for longer anyway.

Edited April 22, 2021 by keefer

[eastglosmog]

10 hours ago, keefer said:

Just to mention how intense the weather event was, which led to the landslip. This was a severe, slow moving thunderstorm(s) which (where I am, in Kirkcaldy Fife) lasted from around 8pm to 5am the next morning.

The only time i can think of one lasting so long and being so intense was probably in August 1975. The lightning was constantly flickering, with many closer strikes and seemingly explosive thunder, and of course torrential rain.

The site at Carmont had this storm for a fraction of the time but the deluge of rain in that period was enough to cause the problems - I shudder to think what the line would've looked like if it had storms for the full duration experienced further south. I expect the line would've been impassable first thing and to a much greater extent - which may mean the accident wouldn't have happened (no trains running) but the line would've been closed for longer anyway.

Using my old NCB guidelines on designing tip drainage systems, 51.5mm over 3.5 hours was about a 1 in 100 year return period storm for the Fife area (differs elsewhere in the UK).  1 in 100year storms are the worst you would normally design for on a tip.  Intensity could have been worse than this, though as bulk of rainfall could have been in a shorter period. 

[Michael Hodgson]

4 hours ago, eastglosmog said:

Using my old NCB guidelines on designing tip drainage systems, 51.5mm over 3.5 hours was about a 1 in 100 year return period storm for the Fife area (differs elsewhere in the UK).  1 in 100year storms are the worst you would normally design for on a tip.  Intensity could have been worse than this, though as bulk of rainfall could have been in a shorter period. 

So does that mean an Aberfan-style landslip once a century is considered acceptable?

[PaulRhB]

8 minutes ago, Michael Hodgson said:

So does that mean an Aberfan-style landslip once a century is considered acceptable?

Thats a bit tabloid in reading it, the post is talking about modern tips with other factors involved on siting too not just drainage. Risk doesn’t just look at drainage in isolation there are other factors that may raise or lower risk too. 

 

4 hours ago, eastglosmog said:

are the worst you would normally design for

Note he says normally design for not ever design for. 

[eastglosmog]

46 minutes ago, Michael Hodgson said:

So does that mean an Aberfan-style landslip once a century is considered acceptable?

Aberfan was not due to excessive rainfall - it was due to crass ignoring of basic civil engineering principles.   Tips designed to current approved principles would not fail in a similar manner.