SCOTLAND faces ‘huge’ bills to upgrade its often Victorian-era railways and drains to cope with the extreme weather provoked by climate change, an expert has warned.

Bob Ward, of the Grantham Institute on Climate Change, believes a national conversation is needed over how to make infrastructure tough enough to withstand global heating.

Scotland was this week hit by brutal floods which severed its two Highland railways and its arterial Edinburgh to Glasgow main line.

Mr Ward warned flood events which we have seen this week are a result of a warming atmosphere and will occur more frequently in the future.

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He said: “The weather in the UK is getting warmer and wetter due to climate change.

“It’s fairly basic physics. When you warm the atmosphere, its capacity to hold water increases. So you get rain falling harder and more frequently than it would otherwise do.

“Ten of the wettest years on record in the UK have happened since 2000, which coincides with 10 of the hottest years as well.

“When these were originally built, engineers designed them to withstand the worst possible circumstances which could happen.

“But what was considered a 1 in 200-year event in Victorian times is possibly a 1 in 100-year event now. Parts of our infrastructure are simply not up to dealing with what is now happening.

“And this is not as bad as it is going to get. Over the next two or three decades, the climate is going to continue to change, no matter how much we cut emissions.

“Anything new being built now has to be built to a higher standard and current infrastructure has to be greatly improved.

“No-one has any idea how much this will cost but the bill will be huge. When infrastructure fails, it has a major impact. People can’t get to work and product doesn’t get to market.

“If we don’t start to tackle it now, we will face even more disruption in the future. The sooner this conversation begins the better. And the first question will be ‘can we afford it?”

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Scottish authorities were yesterday dealing with some already expensive problems. Network Rail, which owns and operates the tracks, said flood damage to the West HighlandLine north of Glasgow was much worse than initially feared.

It had been hoped repair work would allow the line serving Mallaig and Oban to re-open on Monday, after being severed last Sunday.

Helicopters yesterday joined attempts to establish exactly how much material had been washed away at Ardlui and Dalmally by heavy rain on Sunday night.

As a result of the information gathered, it has been decided the line will not fully re-open until August 22.

ScotRail, which is responsible for trains, not tracks, last night said water was receding in the Winchburgh tunnel, which was swamped on Wednesday after Edinburgh suffered a month’s rain in 30 minutes. But it was forced to lay on 18 replacement buses and redirect passengers to other Central Belt lines.

Network Rail said its engineers would inspect the tunnel over night after pumping out two feet of water with the help of firefighters.

Liam Sumpter, its route director for Scotland, said: “We are working as quickly as possible to reduce the water levels so we can inspect the tracks for damage and clear out any sludge or debris that may affect the signalling systems.”

There was around 5cm of rain in Winchurgh. The sheer intensity caused flash flooding across the Lothians and Fife, effectively washing off the Pittenweem Festsival.

A Met Office spokesman said “Edinburgh saw about 34mm of rain in about three hours yesterday afternoon and evening.

“Another 20-30mm of rain could fall from around 6am on Friday until lunchtime. A few showers are likely to follow into the afternoon. There is the risk of heavy and possibly thundery slow-moving showers across Edinburgh through Saturday, giving further rainfall accumulations.”

Edinburgh City Council transport and environment convener Lesley Macinnes, said: “It is almost impossible to avoid the negative effects of freak storms such as these but we’re continuously working to better understand the areas most at risk of flooding, and where we can put measures in place to mitigate this.”

Scenic Loch Katrine, whose waters supply Glasgow, suffered a landslide.