Urban Spatial Distribution Characteristics Of Damaged Landscape Trees Under Typhoon Disaster Based On GIS And CFD Simulation

Typhoons,an extreme climatic disaster,attack south-eastern coastal cities in China every year.Guangdong,as one of the provinces most frequently hit by typhoons in South China for many years,causes countless losses every year.As one of them,the damaged landscape trees not only bring serious problems to the cleaning and maintenance of urban greening,but also bring adverse effects to urban traffic and public safety.Rapid urbanization leads to the rapid increase of urban scale and building density.With the further understanding of urban microclimate,people realize that there is an inseparable relationship between urban space and the quality of urban wind environment.The research on urban wind environment mostly focuses on air quality,environmental comfort,simulation technology,building ventilation,building energy saving and building safety,etc.,and most of them are carried out under the setting of perennial dominant wind.The research of strong wind and typhoon focuses on the response of structure to wind load.However,the researches on typhoon and landscape trees are mostly focused on the wind resistance of trees,while the researches on wind resistance in urban environment are less.Because there is a certain relationship between urban space and the quality of urban wind environment,it is necessary to study the relationship between landscape trees and urban space under typhoon disaster.Based on the data of 569 damaged landscape trees in Guangzhou from 2016 to 2018 under typhoon disasters,this research uses the Geographic Information System(GIS)technology and Local Climate Zone(LCZ)to carry out classified statistics on the spatial distribution of damaged landscape trees based on the urban space.Taking into account the damages of trees,it carries out the discussion and analysis of tree species,damage reasons and other issues.The results show that: 1)Bauhinia spp.,Ficus macrocarpa and Ficus virens are high-risk tree species in typhoon disasters.2)The damaged trees are mainly located in areas with a building density of 30%?50% and most of the LCZ types are compact mid-rise buildings(LCZ 2).3)In typhoon disasters,the damaged landscape trees are mainly distributed in four types of urban morphological space,namely the low-rise mid-rise high-density area,dense-open area,high-rise building fjord area and urban space around viaduct.Furthermore,the CFD simulation software PHOENICS was used to simulate the wind environment of four kinds of urban spaces with more damaged landscape trees,and the wind environment under strong wind and the influence mechanism on trees were discussed,so as to provide reference for landscape tree maintenance and detection and landscape design in typhoon disasters,so as to reduce the impact of secondary disasters on cities.