The Task Force on Tree Management led by the Chief Secretary for Administration published a report entitled "People, Trees, Harmony" in June 2009. Pursuant to the recommendations of the report, the Tree Management Office (TMO) introduced a new tree risk assessment arrangement with the promulgation of detailed guidelines for compliance by tree management departments to better protect public safety.

Tree Risk Assessment Methodology and Procedures

In essence, the objective of tree risk assessment is to reduce the risk posed to personal safety and property by trees that may have problems at locations with high pedestrian and vehicular flow by taking timely action through a systematic methodology and procedures. Tree risk assessment is conducted step-by-step in two stages:

• In the first stage which involves an "area basis" assessment, departments first identify those areas with high pedestrian or vehicular flow under their management.
  
  
• In the second stage involving a "tree basis" assessment, departments carry out tree group inspections in a systematic manner at locations with high pedestrian or vehicular flow to identify trees which may need particular care (such as Old and Valuable Trees and stonewall trees) as well as dead trees and trees with notable health or structural problems which may pose hazards to the public.

According to the tree risk assessment methodology adopted by the TMO, departments conducting tree group inspections will pay particular attention to the following six categories of trees, for which detailed tree risk assessment will be carried out:

1. Old and Valuable Trees;
2. Stonewall trees;
3. Outstanding tree complaints related to structural or health problems;
4. Mature trees with poor health or structure that are of tree species with brittle branches¹;
5. Trees with notable defects or health problems; and
6. Trees growing in very stressful site conditions.

During the detailed inspections, trees are individually assessed for their health and structural conditions more comprehensively.  In addition to visual inspection assisted by simple tools, detailed examination with the assistance of more sophisticated equipment (e.g. resistograph instrument or tomography instrument to check whether there is internal rot or tree cavity) may be conducted if the tree conditions so warrant.

Depending on the tree conditions, appropriate risk mitigation measures (such as pruning, removal of wilted branch, treatment of pest and disease, and cabling and propping to support trees) are prescribed.  If there are no other feasible remedial measures, departments will remove hazardous trees as a last resort so as to eliminate the threat to public safety.

To ensure that the tree risk assessment is properly carried out, tree management departments are required to adopt quality assurance measures such as close supervision of frontline duties and conducting internal audit.  In addition, the TMO carries out desk-top checking of the tree inspection forms completed by departments on a selective basis and random inspection on site of the condition of trees on Government land to ensure that the tree risk assessments are conducted in a professional manner.

Community Surveillance of Trees

In view of the large number of trees in Hong Kong and since the health and structural conditions of trees change in step with their normal lifecycle as well as changes in the external environment, we look to the public for support in helping to monitor the conditions of trees in our community.

To further protect public safety and to facilitate community-wide surveillance, the Development Bureau has uploaded to its tree website information (including location, species, tree conditions and mitigation measures (if applicable), the inspection department, photos and, in some cases, location maps as well) on trees which have undergone detailed inspections by tree management departments in recent months but the improvement measures for which have not yet been completed as well as trees requiring special attention (e.g. Old and Valuable Trees and stonewall trees).

The TMO will continue to work in collaboration with the tree management departments to keep the Tree Register up-to-date.  In addition, tree management departments are taking steps to install labels on those trees included in the Tree Register.

Reporting Problematic Trees

Members of the public may report problematic trees to the “1823” Call Centre.  Operating round-the-clock and with the capability to receive public complaints/enquiries via telephone, email, fax or letter, the “1823” Call Centre serves as an effective, centralised platform for the public to lodge tree complaints and enquiries.

The Efficiency Unit (EU) has launched the “Tell me@1823” app for smart-phones.  Members of the public may submit photographs along with voice descriptions when reporting problematic trees.  Equipped with a geospatial functionality, “Tell me@1823” also captures the physical location of the tree under complaint.

In addition, the "Tree Care Report" standard forms (including e-forms and forms for download) are available on the tree website for members of the public to report suspected problematic trees to the TMO for follow-up action by departments.

Get Prepared for the Wet Season

Tree risk assessment is not a one-off exercise. It needs to be carried out continuously as part of day-to-day tree maintenance work. As living organisms, trees go through the natural cycle: they grow, age, become weak and die.  In preparation for the on-set of the wet season, we have urged the tree management departments to carry out tree risk assessment and tree maintenance properly, and to stay vigilant during the typhoon and rainy season so that appropriate follow-up action will be taken in a timely manner should there be any changes in the conditions of trees under their care.

We hope to work hand-in-hand with the public through community-wide surveillance such that we can carry out our tree risk management work more effectively.

Tree Management Office
Development Bureau
May 2011

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Situation as at 9 January 2012 (website updated as at 9 January 2012) Total number of trees on website 1055

¹ In the course of tree risk assessment in 2011, trees identified as species with brittle branches include Delonix regia (鳳凰木), Erythrina variegata (剌桐), Alstonia scholaris (糖膠樹), Aleurites moluccana (石栗) and Celtis sinensis (朴樹).