Tree policy

Operational policy for the management of trees in the City Council’s control

Introduction

Oxford‘s trees are of immense environmental and aesthetical value to the City and its residents. They brighten up streets, provide a habitat for wildlife, act as the City’s lungs and even help to reduce the rising temperatures caused by climate change. Oxford City Council recognises these benefits, seeking to preserve healthy trees and encourage the planting of new trees where possible. Whilst the majority live and grow without incident, a number of trees located in densely populated cities pose challenges and risks that needs to be  managed. This policy outlines how we intend to increase the number of trees in Oxford, how we manage the tree stock effectively, and how we reduce the risk that certain trees pose to the public. The City Council is responsible for over 102,000 trees, principally those positioned on land owned by the City Council. This tree policy does not cover trees in private ownership which are outside Oxford City Council’s control. Trees in private ownership are the responsibility of the private landowner. If a Tree Preservation Order or a Conservation Area protects trees the Council’s Planning Department administer these controls together with high hedge legislation in consultation with the Arboricultural  Officer 


Aim of the Operational Policy on the Management of trees (Tree Policy) The overall aim of the tree policy is to ensure that

Oxford’s tree stock is retained, enhanced and increased in the most proactive manner whilst ensuring the health, safety and well being of the public and property.  

Management of the Council’s Trees

Oxford City Council is currently undertaking an inspection programme of its trees and from this survey is creating a database of trees and plotting these trees on a geographical information system.

This inspection programme is designed to assess the trees’ condition and health whilst highlighting any work that may be required to ensure the tree is retained in the best possible condition. If a tree is highlighted to be dead, dying, diseased or dangerous and is posing an unacceptable risk to public safety, it will be identified for felling. The decision to prescribe work to a tree is calculated on a risk basis. Risk is calculated through the process of a visual tree assessment (Department of Environment, ‘Research for Amenity Trees No.4 The Body Language of Trees’). An evaluation of the tree takes into account many factors including: 

  • Size
  • Species
  • Presence of structural decay or defects
  • Relationship of any fungal infection relative to species

All these factors are considered in relation to the potential target, the damage that could be caused if the tree were to fail and the likelihood of it doing so.  

If defects are observed, further detailed examination may be carried out using a range of decay detection equipment before any decision is taken regarding the trees future management.  If a contractor, rather than the Council’s own Arboricultural Officer, recommends a tree for felling the Council’s Arboricultural Officer will inspect this tree again prior to the felling taking place to ensure the Officer is confident that this is the correct decision. If the decision of the Council’s Arboricultural Officer is subject to a challenge by a ward member the decision will be reviewed by the Executive Director or his/her nominee.   The Arboricultural Officer will inspect trees for third parties, for example Oxfordshire County Council.  From these inspections, the City Council will only become involved in removal or major works where the work is a benefit to the tree or if the tree poses an unacceptable risk to the public or to property and an appropriate payment is made. These instances will include when a tree is: 

  • Dead
  • Dying
  • Diseased
  • Dangerous
  • Damaging property (e.g. subsidence when confirmed by technical evidence)

However, it must be remembered that the decision about what will be done rests with the owner of the tree. In conjunction with the inspection programme, the Council will maintaina rolling maintenance programme carrying out cyclical works and works highlighted by the inspectors or the Arboricultural Officer. This rolling programme will reduce avoidable risks and issues, for example: 

  • Vehicle and pedestrian collision
  • The removal of identifiable risks
  • The removal or pruning of trees where its relationship to a property causes excessive problems.
  • Obstructing footpaths or driveways by branches or epicormic growth

Felling will not be undertaken for the following reasons: 

  • Blocking light
  • Television or satellite signals
  • Residents do not ‘like’ the tree
  • Leaf or fruit drop
  • Unproven allegations of subsidence or direct damage
  • Construction of dropped kerbs or new driveways
  • Perceived threat
  • The tree’s size; ‘its got too big’
  • The tree ‘ moves in the wind’
  • Bird droppings
  • Aphids
  • Individuals medical conditions
  • Erection of fencing, walls, play areas and sports pitches

The above is not a exhaustive list but is representative of a large number of customer enquiries. Further to an inspection the Arboricultural Officer may agree to undertake a variety of pruning operations to remedy complaints provided that the long-term health, appearance, or potential development of the tree is not affected. As part of good arboricultural management the removal of trees will be carried out when the removal will benefit the long-term development of adjacent better quality trees i.e. woodland and copse management. Furthermore, formative pruning may be carried out following the Arboricultural Officer’s inspections, for example: 

  • Removal of crossing, weak or competitive branches
  • Crown balancing
  • Dead wooding
  • Crown lifting
  • Crown thinning

All waste from tree surgery will be recycled, being used in a variety of situations, including: mulches for shrub beds, power station fuel, firewood, habitat piles or dead standing timber where suitable, thereby avoiding the use of landfill sites. 

Wildlife and Conservation

Tree works shall be carried out whilst ensuring adherence to all wildlife and conservation laws are adhered to including: 

·        Wildlife and Countryside Act 1981·        Wildlife and Countryside (Amendment) Act 1999·        Countryside Rights of Way Act 2000·        Town and Country Planning Act (Trees) Regulations 1999·        Conservation (Natural Habitats) Regulations 1994·        European Habitats Directive 1992·        Biodiversity Act 2005 The authority recognises the different levels of risk represented by a hazard tree when it is located in different sites and will manage them in accordance with Department of Environment Research for Amenity Trees No. 7 ‘Principals of Tree Hazard Assessment and Management’.  

Higher levels of risk will be acceptable in locations where there is a lower footfall e.g. middle of a woodland area as apposed to a highway situation. This will allow the retention of veteran trees without undue risk whilst encouraging bio-diversity and habitat retention. When any works are recommended for trees within a Conservation area the Arboricultural Officer will liaise with the Council’s Planning Department although there is no legal obligation to do this. 

Communicating with the public and members

The Council will inform Ward Councillors of any major tree works such as pollarding or felling before any works are carried out in their ward. The Council will also erect notices on trees or on park entrances to inform the public of the proposed works. The

Forest of Oxford will be advised of major tree works.  In the event of emergency health and safety work that must be carried out immediately (e.g. storm conditions), the Arboricultural Officer will notify Ward Councillors retrospectively. Felling is the last resort and will only be carried out when deemed necessary by the Arboricultural Officer. However, public safety is paramount and for this reason the public will be informed of tree works, via Ward Councillors and notices, but will not be consulted for approval. 

Council Trees and Development

Requests for tree works and/or removal of trees from Council owned land to allow development shall be considered by the elected members at an Area Committee as part of the decision as to whether to approve the planning application. Officers will not take this decision, although advice will be provided to the elected members. Members are encouraged to consider when dealing with planning applications for privately owned land, whether there are Council owned trees on adjacent plots that may be affected by the development before approving the application (e.g. for site access, dropped kerbs or storage of materials). 

Subsidence

Subsidence is a complex interaction between the soil, building, climate and vegetation that occurs on highly shrinkable clay soils when the soil supporting all or part of a building dries out and consequently shrinks, resulting in part of a building moving downwards. Trees lose water from the leaves through transpiration that is replenished by water taken from the soil by the roots. If the tree takes more water from the soil than is replaced by rainfall the soil will gradually dry out. Trees have a large root system and they can dry the soil to a greater depth, critically below the level of foundations. The amount of water trees can remove from the soil can vary between different species. This policy seeks to set out the Council’s response to subsidence claims against its own trees. The opposite of subsidence is a process called ‘heave’ and this occurs as a shrinkable clay soil re-hydrates (becomes wet again) and begins to increase in volume exerting upward pressure. Heave can also cause damage to buildings and is just as undesirable as subsidence but occurs less frequently.  

All claims regarding subsidence will be referred to the Council’s Insurer along with a brief report from the Council’s Arboricultural Officer. The report will highlight if the tree is the responsibility of the Council, the age, type, and condition of the trees and any other factors that may be of importance to the claim. The insurers for the claimant or their consultants must provide evidence of ALL the following items before any works are carried out to Council owned trees. 

  • Physical damage
  • Presence of live roots of a suitable species
  • Seasonal movement or variation of the damage during different seasons.

If the above evidence is provided, the Council will adhere to the advice supplied by insurers with regard to what, if any, works are required to the trees. If evidence is insufficient any claim will be dismissed. 

Replacement Trees

It is the City Council’s policy that every tree felled should be replaced to ensure that over the years the City retains its tree stock for future generations, although it is recognised that it is not always practical or prudent to replace a tree in the same location or with the same species that was previously planted. The Council will work proactively to manage or facilitate replacement tree planting, which may include but not be limited to, working with the community and friends groups, considering new planting schemes, including memorial trees, community woodlands and by encouraging funding from new developments for tree planting through working with the Planning Department.  Each year, the Council will update and publish a programme for planting in the year reflecting the approved budget. 

Procedures

This policy will be supported by Operational Procedures in the Parks Service to ensure compliance. Attached in Appendix 1 is the ‘Procedure – Arboricultural Works on Trees’. This is used only when a tree inspection highlights that works are required based on the Arboricultural Officer’s inspection in line with this policy. 

Author: Stuart FitzsimmonsAssistant Parks Manager25/10/2007Amended 15/02/2008
Definitions Arboriculture – the management of trees in the urban environment 

Good Arboricultural Practice – appropriate tree surgery operations carried out at suitable times to promote the quality of trees and their enduring relationship with the urban environment. Minor Roads – Footpaths, bridleways and ‘urban roads’ that are neither ‘trunk’ nor ‘classified’, usually with a speed limit of 30mph. These roads are the responsibility of the City Council as outlined in the Section 42 agreement with Oxfordshire County Council. 

Geographical Information System (G.I.S) – Computer database usually represented as a map with linked tables of data. Dead, Dying, Diseased – see Dangerous 

Dangerous – a tree can be classified as dangerous, posing a more than acceptable risk to persons or property, having been assessed of its chance of collapse and the potential damage that may result if it collapsed. Failure Risk Assessment – An assessment based on 

How could the tree fail, what defects are present, probability of failure?Followed byConsequential Damage – what damage would the failure cause?Followed byHazard Reduction – if more than acceptable risk present, tree pruning, removal, or relocate targets appropriate to each situation. Decay Detection Equipment – a range of tools specifically designed to measure the extent of decay or remaining healthy timber in an individual tree. Tools currently owned by Oxford City Council include mallet, probe, resistograph micro-drill, core sampler, fractometer, Picus sonic tomography. Major Works – works including felling or work concentrated on many trees in a localised area. 

Pollarding – the removal of all branches, leaving a trunk from which new branches will grow in successive seasons. Usually on a 5 – 15-year cycle, limited to a small number of species. Physical Damage – damage, usually cracking, to structures caused by incremental growth of stems or roots, or soil shrinkage due to water extraction. 

Presence of live roots – taken from test boreholes dug in the area adjacent to property damage as evidence towards proving subsidence of a property. 

Seasonal Movement – physical damage to structures that increases with annual growth relating to direct damage. If subsidence is present the cracking will increase in summer and reduce in winter. (Deciduous trees extract large volumes of water during summer months and dramatically less in winter when trees are without leaves.) Cyclical Works – removal or adjustment of stakes and ties from young trees, removal of basal or epicormic growth, crown lifting to clear footpaths or highway vision splays.

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