1. GETTING TO GRIPS WITH SUBSIDENCE
Dr Giles Biddle
and
Dr Martin Dobson

2. Introduction and background to subsidence problems
Dr Martin Dobson

3. Our story begins in the 1970s…
…when fashion sense was questionable
and subsidence became an ‘insured peril’

4. It continues in 1976… …which coincides with the first commercial
flight of Concorde on 21 January

5. Apple Computers on 1 April
…with the formation of
Apple Computers on 1 April

6. …with water rationing in Cardiff on 9 August

7. 1976
The long hot summer of 1976 was the longest recorded in England and Wales since 1727.

8. 1976
For several weeks in July and August, large parts of the country got no rainfall at all leading to the drying up of reservoirs and a severe drought.
Staines reservoir

10. 1976
Finally the Labour government of the time appointed a minister for drought…
Denis Howell
…as if on cue the rain began to fall.

11. SUBSIDENCE

12. SUBSIDENCE

16. What kind of damage are we
talking about?

26. Legal framework
Case law (common law)

27. Trespass

28. A trespass is the wrongful invasion of another's property.
Every unlawful entry onto another's property is trespass, even if no harm is done to the property
Trespassing root (naughty!)

29. Nuisance

30. Unfortunately trees can’t read!
Nuisance
Unfortunately trees can’t read!

31. Nuisance A private nuisance is an interference
with a person's enjoyment and
use of his land.

32. Negligence
A person has acted negligently if he/she has departed from the conduct expected of a reasonably prudent person acting under similar circumstances

33. Reasonable Foreseeability
a danger which a reasonable person should anticipate as the result from his/her action or inaction

34. Solloway v Hampshire County Council (1981)
HCC were appealing against a previous judgement made against them in favour of a home owner Mr B. Solloway.
Subsidence damage had been caused to the house by a Horse Chestnut owned by HCC.
Judgement was made that the encroachment of the tree roots constituted a nuisance and HCC were responsible for damage caused.
However, geological maps showed that whilst the house was on plateau gravel sections of it rested on small pockets of clay which were not shown on geological maps.
The Court of Appeal ruled that the existence of small clay pockets beneath the house was not reasonably foreseeable and hence there was no breach of duty on the part of HCC. The appeal was allowed.

35. Paterson v Humberside County Council (1995)
Damage to a house caused by two Lime trees owned by Humberside County Council.
It was noted that although the house had shallow foundations and was thus more susceptible to damage this had no relevance to liability – ‘the tree takes its victim as it find it’
An argument was made on behalf of the plaintiffs that there was no need to establish foreseeability. This was rejected by the judge who said the test for such foreseeability was whether the risk was one which a reasonable person in the defendants position would have regarded as a real risk.
The Council was deemed to know that damage was a ‘real risk’ as it advised householders of safe distances from buildings to plant trees.

36. Delaware Mansions v Westminster City Council (1999)
In 1989 a Plane tree owned by Westminster City Council caused damage to some flats. Engineers recommended underpinning of the flats or removal of the tree. The council refused to remove the tree.
The flats were sold in June 1990 to the second appellant company for one pound. However, their claim for damages was dismissed on the grounds that they could not claim because the damage had occurred before they became the owners.
The plaintiffs appealed and won. "Thus, where there is a continuing nuisance, the owner is entitled to … damages "
"If the council had agreed to remove the tree when asked, the damages would have been very small…the fact that the nuisance existed before the second appellant became the owner is irrelevant".

37. Jones v Portsmouth City Council (2002)
The key issues were whether subsidence had been caused by the defendant’s Plane trees, whether the council were responsible and whether or not the council had been given sufficient notice to abate the nuisance.
The judge ruled that the trees had caused damage and that despite the soil being ‘brick earth’ it was a foreseeably shrinkable soil.
On the matter of reasonable notice to abate the judge said:
‘the fact is that the defendant was notified of the claim before the claimant was committed by contract to the underpinning ’ and therefore ‘the defendant was not deprived of a reasonable opportunity to abate the nuisance’ .

38. Loftus Brigham v London Borough of Ealing (2003)
The issue was subsidence caused by either the claimant’s Virginia creeper and/or Wisteria or the defendant’s Plane trees
Original ruling - ‘The Claimants need to show that the Defendants’ trees were probably the dominant cause and they have not convinced me that such was established’
On Appeal the ruling was that the proper test was whether the tree roots were the ‘effective and substantial’ cause of the damage or alternatively whether they ‘materially contributed to the damage’.

39. Raphael v London Borough of Brent (2007)
The issue was whether level monitoring only was adequate to establish that subsidence had occurred.
There were no soil, foundation or root investigations. Neither was any crack monitoring carried out.
The secondary issue was which vegetation caused the damage. Was it the claimant’s Wisteria and Cherry or the council’s Plane(s)?
The judge ruled out the claimant’s vegetation as a cause of damage and gave judgement against the council.

40. PLANE
CHERRY

41. London Tree Officer’s Association

42. Identify those trees that are most likely to cause subsidence damage and subject them to a regular and systematic pruning regime.
Make the identification of the above trees an on going process within the normal tree inspection programme.
Investigate all potential subsidence claims that may implicate trees and take prompt action (i.e. investigate the site and, if appropriate, carry out precautionary pruning). If ground conditions recover subsequent to precautionary pruning the potential claim may not be lodged. By taking prompt action boroughs can eliminate or mitigate a potential claim.
All claims should be assessed and remedial pruning carried out as soon as practically possible, except where the claims are clearly unreasonable or erroneous.
Before undertaking further pruning or contemplating tree removal the authority should insist that the claimant provide adequate evidence in support of the claim.

43. Identify those trees that are most likely to cause subsidence damage and subject them to a regular and systematic pruning regime.
Make the identification of the above trees an on going process within the normal tree inspection programme.
Investigate all potential subsidence claims that may implicate trees and take prompt action (i.e. investigate the site and, if appropriate, carry out precautionary pruning). If ground conditions recover subsequent to precautionary pruning the potential claim may not be lodged. By taking prompt action boroughs can eliminate or mitigate a potential claim.
All claims should be assessed and remedial pruning carried out as soon as practically possible, except where the claims are clearly unreasonable or erroneous.
Before undertaking further pruning or contemplating tree removal the authority should insist that the claimant provide adequate evidence in support of the claim.

44. Identify those trees that are most likely to cause subsidence damage and subject them to a regular and systematic pruning regime.
Make the identification of the above trees an on going process within the normal tree inspection programme.
Investigate all potential subsidence claims that may implicate trees and take prompt action (i.e. investigate the site and, if appropriate, carry out precautionary pruning). If ground conditions recover subsequent to precautionary pruning the potential claim may not be lodged.
All claims should be assessed and remedial pruning carried out as soon as practically possible, except where the claims are clearly unreasonable or erroneous.
Before undertaking further pruning or contemplating tree removal the authority should insist that the claimant provide adequate evidence in support of the claim.

45. Identify those trees that are most likely to cause subsidence damage and subject them to a regular and systematic pruning regime.
Make the identification of the above trees an on going process within the normal tree inspection programme.
Investigate all potential subsidence claims that may implicate trees and take prompt action (i.e. investigate the site and, if appropriate, carry out precautionary pruning). If ground conditions recover subsequent to precautionary pruning the potential claim may not be lodged.
All claims should be assessed and remedial pruning carried out as soon as practically possible, except where the claims are clearly unreasonable or erroneous.
Before undertaking further pruning or contemplating tree removal the authority should insist that the claimant provide adequate evidence in support of the claim.

46. Identify those trees that are most likely to cause subsidence damage and subject them to a regular and systematic pruning regime.
Make the identification of the above trees an on going process within the normal tree inspection programme.
Investigate all potential subsidence claims that may implicate trees and take prompt action (i.e. investigate the site and, if appropriate, carry out precautionary pruning). If ground conditions recover subsequent to precautionary pruning the potential claim may not be lodged.
All claims should be assessed and remedial pruning carried out as soon as practically possible, except where the claims are clearly unreasonable or erroneous.
Before undertaking further pruning or contemplating tree removal the authority should insist that the claimant provide adequate evidence in support of the claim.

48. Joint Mitigation Protocol
May 2008
Aims to:
Speed up the process of claims handling, decision making and mitigation implementation leading to resolution
Recognise the value of trees in the built environment
Provide local authorities with all the investigative evidence required at the beginning of the process.

49. Joint Mitigation Protocol
May 2008
7 days notify tree owner of damage
14 days after receipt of notification tree owner to supply details of:
- Contact person
- Insurer
- CAVAT value of tree - low (less than £5,300) medium (£5,300 to £17,500) high (greater than £17,500).
60 days submission of evidence in support of claim
13 weeks from receipt of the evidence to undertake the mitigation.

51. ABI DOMESTIC SUBSIDENCE TREE ROOT CLAIMS AGREEMENT THIRD PARTY LIABILITY Every insurer subscribing to this Agreement agrees -
1 that where a claim arises in respect of subsidence and where damage to the building and/or contents has been caused wholly or partly by tree root encroachment the insurer holding the buildings and/or contents insurance for the damaged property undertakes to investigate, handle and where appropriate meet the claim on the basis of their policy cover;
2 not to pursue recovery against the insurers of the owned/tenanted/ occupied property responsible for the liability of the tree root encroachment regardless of whether the damage has been caused wholly or partly as a result of the tree root encroachment;
3 that in the event of there being a recurrence of damage or no reasonable preventative measures being taken by the person/persons who have liability for the tree root encroachment this Agreement will have no effect in regard to any subsequent claim.
4 that this Agreement will have no bearing or consideration in any uninsured loss claim which may be pursued against the person/persons having a potential liability for the tree root encroachment".

52. ABI DOMESTIC SUBSIDENCE TREE ROOT CLAIMS AGREEMENT THIRD PARTY LIABILITY Every insurer subscribing to this Agreement agrees -
1 that where a claim arises in respect of subsidence and where damage to the building and/or contents has been caused wholly or partly by tree root encroachment the insurer holding the buildings and/or contents insurance for the damaged property undertakes to investigate, handle and where appropriate meet the claim on the basis of their policy cover;
2 not to pursue recovery against the insurers of the owned/tenanted/ occupied property responsible for the liability of the tree root encroachment regardless of whether the damage has been caused wholly or partly as a result of the tree root encroachment;
3 that in the event of there being a recurrence of damage or no reasonable preventative measures being taken by the person/persons who have liability for the tree root encroachment this Agreement will have no effect in regard to any subsequent claim.
4 that this Agreement will have no bearing or consideration in any uninsured loss claim which may be pursued against the person/persons having a potential liability for the tree root encroachment".

53. ABI DOMESTIC SUBSIDENCE TREE ROOT CLAIMS AGREEMENT THIRD PARTY LIABILITY Every insurer subscribing to this Agreement agrees -
1 that where a claim arises in respect of subsidence and where damage to the building and/or contents has been caused wholly or partly by tree root encroachment the insurer holding the buildings and/or contents insurance for the damaged property undertakes to investigate, handle and where appropriate meet the claim on the basis of their policy cover;
2 not to pursue recovery against the insurers of the owned/tenanted/ occupied property responsible for the liability of the tree root encroachment regardless of whether the damage has been caused wholly or partly as a result of the tree root encroachment;
3 that in the event of there being a recurrence of damage or no reasonable preventative measures being taken by the person/persons who have liability for the tree root encroachment this Agreement will have no effect in regard to any subsequent claim.
4 that this Agreement will have no bearing or consideration in any uninsured loss claim which may be pursued against the person/persons having a potential liability for the tree root encroachment".

54. ABI DOMESTIC SUBSIDENCE TREE ROOT CLAIMS AGREEMENT THIRD PARTY LIABILITY Every insurer subscribing to this Agreement agrees -
1 that where a claim arises in respect of subsidence and where damage to the building and/or contents has been caused wholly or partly by tree root encroachment the insurer holding the buildings and/or contents insurance for the damaged property undertakes to investigate, handle and where appropriate meet the claim on the basis of their policy cover;
2 not to pursue recovery against the insurers of the owned/tenanted/ occupied property responsible for the liability of the tree root encroachment regardless of whether the damage has been caused wholly or partly as a result of the tree root encroachment;
3 that in the event of there being a recurrence of damage or no reasonable preventative measures being taken by the person/persons who have liability for the tree root encroachment this Agreement will have no effect in regard to any subsequent claim.
4 that this Agreement will have no bearing or consideration in any uninsured loss claim which may be pursued against the person/persons having a potential liability for the tree root encroachment".
Provided that:
(i) Immediate notice shall be given to the other insurer by the insurer to whom the claim is notified, together with copies of all relevant reports (including covering letters) from loss adjusters, engineers, surveyors and the like.

55. Subsidence risk assessment
SRA developed by the Arboricultural Association in 1998 in response to requests by the mortgage and insurance industry
Withdrawn in 2001 as it didn’t accurately predict subsidence risk

56. Subsidence risk assessment

57. Subsidence risk assessment

58. Subsidence risk assessment
SRA developed by Royal and Sun Alliance
TreeRAT

59. Subsidence risk assessment
6th September 2006 –new subsidence risk model, Arborisk™, for Greater London (woo hoo!)
Aerial photography and Infoterra’s lidar1 height data has been used to establish the proximity of trees to properties, as well as the height and canopy size – from which the current and future size of the root zone can be determined.
With this tree root zone data and soil type data, also included, the model can quickly produce accurate (?) subsidence risk assessments for individual properties.