Trees serve as a natural umbrella to mitigate insolation absorbed by features of the urban environment, especially building structures and pavements. For a desert community, trees are a particularly valuable asset because they contribute to energy conservation efforts, improve home values, allow for cost savings, and promote enhanced health and well-being. The main obstacle in creating a sustainable urban community in a desert city with trees is the scarceness and cost of irrigation water. Thus, strategically located and arranged desert trees with the fewest tree numbers possible potentially translate into significant energy, water and long-term cost savings as well as conservation, economic, and health benefits. The objective of this dissertation is to achieve this research goal with integrated methods from both theoretical and empirical perspectives.
This dissertation includes three main parts. The first part proposes a spatial optimization method to optimize the tree locations with the objective to maximize shade coverage on building facades and open structures and minimize shade coverage on building rooftops in a 3-dimensional environment. Second, an outdoor urban physical scale model with field measurement is presented to understand the cooling and locational benefits of tree shade. The third part implements a microclimate numerical simulation model to analyze how the specific tree locations and arrangements influence outdoor microclimates and improve human thermal comfort. These three parts of the dissertation attempt to fill the research gap of how to strategically locate trees at the building to neighborhood scale, and quantifying the impact of such arrangements.
Results highlight the significance of arranging residential shade trees across different geographical scales. In both the building and neighborhood scales, research results recommend that trees should be arranged in the central part of the building south front yard. More cooling benefits are provided to the building structures and outdoor microclimates with a cluster tree arrangement without canopy overlap; however, if residents are interested in creating a better outdoor thermal environment, open space between trees is needed to enhance the wind environment for better human thermal comfort. Considering the rapid urbanization process, limited water resources supply, and the severe heat stress in the urban areas, judicious design and planning of trees is of increasing importance for improving the life quality and sustaining the urban environment.
Golf courses require large amounts of water and other resources. The Southwestern United States has experienced rapid population growth, coupled with a dramatic increase in the built environment and golf courses. This paper aims to assess the environmental sustainability of golf courses in the Phoenix Metropolitan area at multiple scales in terms of water, ecosystem services and management practices. We report on the number and spatial distribution of golf courses, the amount of water used by them, the ecosystem services they provide, potential social injustice issues within the area, and the sustainability of management practices. There are 197 golf courses within the Phoenix Metropolitan Area, which are composed of 465 patches covering an area around 57 square miles. The golf courses within the Phoenix Active Management Area use around 500 acre-feet of water per year. Golf courses are categorized as an industrial water user and account for roughly half of all industrial water use in the Phoenix Active Management Area. The primary water source for golf courses is groundwater, with effluent as their second most-used source. Most golf courses are located in areas with a median household income between $61,333-$90,185 and only one was located in an area with a median household income below $27,393. Golf courses in the region provide a number of ecosystem services and help the local economy in multiple ways. However, given the scarcity of water and the projected drier and hotter climate in the American Southwest, we suggest curbing the expansion of golf courses and implement more sustainable management practices.