The Risk Assessment Of Trees In Housing Estates By Hong Kong Special Administrative Region Government

With the increasing economic growth,Hong Kong become one of the highest population cities since 1960 s.However,higher dense population occupy massive land which lead to the greening space are very limited in Hong Kong.In order to provide comfortable living environment and improve the living quality of public estate,plantation could offer a beautiful and healthy greening environment.Tree Risk assessment can protect social public safety and extend the life cycle of trees.Tree managers are responsible for providing reports of risk assessment to relevant government departments with conducting regular surveys and assessments of the safety status of urban trees.Hong Kong government manage the trees on the government land with integrated approach.When any healthy,structural or other problems of the tree has reported in the trees risk assessments,the government should employ some experts to monitor these problematic trees and take some mitigation measures,such as pruning,pest control or installing structural support etc.This case study focused on the trees risk assessment of six public estates in Hong Kong,which are Un Chau Estate,Ap Lei Chau Estate,Wah Kwai Estate,Lai Kok Estate,Yiu Tung Estateand and Lok Man Sun Chuen.These housing estates have different tree species,included Old and Valuable Trees(OVT)and newly planted trees.The results of the assessment showed that Mimosaceaeare is the most common and the highest quantity group among these housing estates.And 77.22% of overall tree varieties are exotic tree species,and only 22.78% are local tree species,it indicated that the trees selection of the public housing estate tends to exotic tree species in Hong Kong.With classified the trees in these 6 housing estates into four phases according to their life cycle,newly planted,young,mature and removed,60% of these trees are mature trees.Even through the trees in the housing estates are facing different biological,physical and environmental problems,the assessment reflected that 98% of trees are classified as healthy and only 2% classified as unhealthy.Among the trees of these six housing estates,34 trees(1.1%)should be removed after conducted tree risk assessment,and 111(3.6%)of the trees should be pruned.These results showed that the tree maintenances are able to enhance the growth of the trees.The reasonable and locational distribution are essential for improving the air quality and living environment.It is widely using in other countries in the world to conduct tree risk assessment by measure the Diameter at breast height(DBH),tree height and crown spread.The evaluation methods and cases of this study can be recommended in tree risk assessment in other cities,especially the PiCUS Sonic Tomography method of tree trunk internal structure,which is very accurate and simple to detect the damage inside the trunk.It is a very effective monitoring technique for trunk structure and can be widely used.