A simple method for designation of urban ventilation corridors and its application to urban heat island analysis

This paper describes urban wind ventilation mapping, using the concept of "building frontal area index", and uses the Kowloon peninsula of Hong Kong as an example of a dense, sub-tropical urban environment where ventilation is critical for human health. The frontal area index is calculated for uniform 100 m grid cells, based on three dimensional buildings in each cell, for eight different wind directions. The frontal area index is then correlated with a land use map, and the results indicate that high density commercial and industrial areas with large building footprints had higher values than other urban land use types. Using the map of frontal area index, the main ventilation pathways across the urban area are located using least cost path analysis in a raster GIS. Field measurements of urban winds confirmed the significance and functionality of these modelled ventilation paths. Comparison of the pathways with a map of the urban heat island suggests that ventilation is a key parameter in mitigating heat island formation in the study area. Planning and environmental authorities may use the derived frontal area index and ventilation maps as objective measures of environmental quality within a city, especially when temperatures in the inner city are a major concern.