The Impact of Zoning on Urban Tree Canopy Development

Urban trees form a vital backbone of the green infrastructure crucial to urban processes in the 21st century. In light of major urban flooding events within the past year in Texas and the increasing frequency of record heat... [ view full abstract ]

Urban trees form a vital backbone of the green infrastructure crucial to urban processes in the 21st century. In light of major urban flooding events within the past year in Texas and the increasing frequency of record heat waves throughout the United States, it is more important than ever before to re-evaluate this green infrastructure within our built environments. Most existing research focuses on the disparities between broad types of Euclidean zones (i.e. differences in canopy cover among residential, retail, and commercial districts.) Little research, however, delves into the more fine-grained, specificities of these classifications that account for differential outcomes. This paper seeks to identify best zoning practices promote urban tree canopy development and maintenance in suburban settings. More specifically the aim is to ask and answer, which specific zoning factors exert the greatest influence on disparities in tree canopy coverage of comparable use classification between municipalities? Factors that are the direct object of study include lot size, coverage requirements, and parking requirements.

Using aerial orthophotography from the National Agricultural Imagery Program (NAIP), breakdowns of land cover for two comparable mid-size cities (Irving, TX and Garland, TX) were obtained as well as a general breakdown of land cover in Dallas County as a whole as a reference dataset. From the results it appears that Irving’s municipal code better maximizes potential canopy cover in single-family districts whereas Garland’s code better utilizes potential canopy coverage in its urban districts. This points to the influence of municipal land-use priorities on the differences in canopy coverage and maximization metrics. A better understanding of the nuances in practices that promote canopy growth in different land-use categories will allow urban foresters to fine-tune their strategies and improve outcomes with policy solutions better tailored to specific district uses.