British sinkhole spike prompts warning

 

David Shukman examines how and why sinkholes form

Britain is likely to face the strange and disturbing threat of more sinkholes opening up in the weeks and months ahead.

The warning comes from the British Geological Survey (BGS), which has been studying a recent spate of collapses across the country.

In a typical year, geologists would expect to see one or two sinkholes appearing, but this month's tally has reached six so far.

Dr Tony Cooper of the British Geological Survey told me that some areas of the country are more susceptible than others, depending on the type of rock involved.

Gypsum is vulnerable to being rapidly eroded by water - and this is what underlies Ripon where a house collapsed when a sinkhole appeared this morning.

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One of life's greatest certainties is that the ground is solid beneath one's feet so the sudden appearance of chasms, however small, is unsettling.”

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Dr Cooper said: "If you took a chunk of gypsum the size of a van and left it in a river it would be dissolved in about 18 months."

Another key factor is the nature of the geology itself: Some rocks host networks of natural caverns while others are riddled with old mineshafts.

Depending on the soil and rock suspended above of these cavities, a sudden incursion of water from heavy rainstorms can lead to massive strains and, ultimately, to collapse.

One particularly large sinkhole opened in Hemel Hempstead on Saturday - and the hole has expanded since then.

As many as 20 families have been forced to evacuate, 12 because their homes are deemed to be unsafe and the rest because gas supplies have had to be cut off.

Concrete solution

The hole itself runs under the corner of a house and under part of road. The tarmac has collapsed and the bare earth lies exposed.

The engineer brought in to examine the site, Clive Edmunds, told me he was hoping to fill the hole with concrete later this week.

"We estimate that it will need between 100-200 cubic metres of concrete - which is equivalent to 10-20 truck loads but there may be connections to further voids below," he said.

The house above the hole is still standing but there are fears that it may collapse soon. The road beside it is slightly buckled.

Such is the danger that neighbours were warned to leave so rapidly, many have had to abandon cars in their driveways.

Hemel Hempstead sinkhole Another, 35ft-wide, hole opened up in Hemel Hempstead at the weekend

Although sinkholes open up for all kinds of reasons, by far the most common cause is a sudden influx of water.

This winter's rain is the obvious suspect and its effects look set to continue.

Dr Cooper believes further sinkholes are likely and not only because of the saturated ground.

"I do expect to see more of these - we are seeing a much higher rate than normal," he said.

One cause can be changes in the flow of groundwater, including when it is drained away which means the process of drying out may trigger another spate of these strange threats.

Even at a safe distance, the sinkhole at Hemel Hempstead was a surprisingly frightening sight.

One of life's greatest certainties is that the ground is solid beneath one's feet so the sudden appearance of chasms, however small, is unsettling.

The 20 families who have to move out of their homes in Hemel Hempstead have no idea how long they will need to stay away.

The housing association which runs the estate hopes the first families will be allowed back in a week but officials acknowledge it may take much longer.

This is shaping up to be yet another painful legacy of Britain's winter of storms.

 
David Shukman Article written by David Shukman David Shukman Science editor

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  • rate this
    0

    Comment number 306.

    I predict Politicians and Journalists/Commentators will blame this on:

    1) The Environmental Agency.
    2) The EU.
    3) Welfare.

  • rate this
    +1

    Comment number 305.

    Where is it safe to live?

  • rate this
    -1

    Comment number 304.

    How come people have never heard of sink holes, while is it happening now. Don't tell me it's been happening for years. Rubbish.

  • rate this
    -1

    Comment number 303.

    There will always be sink holes they takes year to form its all part of nature, geology, the planets fun time to surprise people,
    Not because of the bad weather we have just had, only dummy's will believe its all the rain.

  • rate this
    0

    Comment number 302.

    Properties these days are thrown up cheaply and that is your porblem insufficeint drainage. When a new row of houses are built they just connect them to the existing sewers. They should start adding underground storage tanks for rain water they have done this at Sankey for Penketh in Warrington, Cheshire they used to suffer from flooding every year and this year none.

  • rate this
    0

    Comment number 301.

    I made a good prediction about so many sick holes opening up.
    Even if the rain does subside for the moment, I think we'll be see a lot more of sinkholes in the future and rain just as bad.

  • rate this
    +2

    Comment number 300.

    299.DuaneK
    17 Minutes ago
    The houses affected in Hemel Hempstead look relatively new don't they? If that's the case, would ground tests not have been done on these areas prior to foundations being laid.

    +++

    Having seen how builders work on insurance work, I wouldn't take that on trust. They were quite prepared to use surface filler on deep structural cracks.

  • rate this
    +3

    Comment number 299.

    The houses affected in Hemel Hempstead look relatively new don't they? If that's the case, would ground tests not have been done on these areas prior to foundations being laid. Most sinkholes take years to form.
    And if you build on top of abandond mineshafts, you fill them in first prior to building even just to protect against subsidence. That's nothing new.

  • rate this
    +1

    Comment number 298.

    295.classicno9
    11 Minutes ago
    #291 Bav

    We should also not forget the classic case of Riggins, Texas and what happened there. Indeed, what would Riggins do now, given everything?

    +++

    Did it cause the sinkholes in Florida?

  • rate this
    -1

    Comment number 297.

    295.classicno9

    I'm sorry... I misread the situation!

    Too late, play's over. You waited too long to make a decision. Now we lost the game because of you, now we're not going to state, and now the whole town of Dillon hates you and you're never going to get laid. FACT.

  • rate this
    +2

    Comment number 296.

    The radio active waste is actully naturally ocurring known as NORM. Radioactivity is quite natural nothing to worry about unless it leaks out into your house as in parts of derbyshire and cornwall when houses have to be force ventilated to remove radon.

  • rate this
    0

    Comment number 295.

    #291 Bav

    We should also not forget the classic case of Riggins, Texas and what happened there. Indeed, what would Riggins do now, given everything?

  • rate this
    +2

    Comment number 294.

    For those not in the know, Ripon sits on a Gypsum fault and such "sink-holes" are not an unusual feature, although relatively rare occurrences after periods of heavy rain and flooded river(s) holes have appeared in the past. It's regrettable, but people should not think that this is a new occurrence. As for linking this to Fracing - this is just plain ridiculous scaremongering.

  • rate this
    -1

    Comment number 293.

    #291 Bav

    Quite. Some people will have you believe that we Can't Lose with fracking, but the threat of a black hole does cast some doubt over that assertion.

  • rate this
    +2

    Comment number 292.

    291.bav
    6 Minutes ago
    287.classicno9

    Indeed, and as the independent has pointed out in some of its sterling "non-biased" articles, fracking will increase the chances of said ambush of sinkholes significantly.

    I for one intend to approach this topic with clear eyes and a full heart.

    +++

    Where was the "fracking" performed that caused the latest batch of sinkholes?

  • rate this
    -1

    Comment number 291.

    287.classicno9

    Indeed, and as the independent has pointed out in some of its sterling "non-biased" articles, fracking will increase the chances of said ambush of sinkholes significantly.

    I for one intend to approach this topic with clear eyes and a full heart.

  • rate this
    +2

    Comment number 290.

    288. CURTAINS 2012

    Undeniable logic, but my comment was aimed at the general state of society rather than the BBC specifically. Did you see the other day? 20,000 online protesters about 6 ill-kept horses, fair. Zero protesters about 26m ill-kept people in NK.

    We're being flooded with information that is irrelevant, which is why more people see articles like this that don't directly affect them.

  • rate this
    -5

    Comment number 289.

    Stop the fracking.

  • rate this
    +3

    Comment number 288.

    286.bro3886
    17 Minutes ago
    279. Dave

    The sinkhole stories didn't reach the "Top Read" section of BBC in the past. In general, we all hear news that is less important to us specifically nowadays,

    +++

    That would be because at least ten other articles had more readers than this one. It's NOT a BBC conspiracy.

  • rate this
    -2

    Comment number 287.

    #281 Bav

    You raise an interesting point...I consulted the oracle and the ancient runes and they attest to "herds" of sinkholes that would blight future societies. But if you delve deeper, to ancient Mayan predictions, they speak of an "ambush" of sinkholes, that, as we all know, eventually form a black hole.

 

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