Beyond 'Green' streets - Mitigating climate change through residential streetscape design

Abstract

This research Beyond ‘Green’ Streets identifies significant gaps in theory and practice and proposes, develops and applies new techniques to mitigate climate change through residential street design. References to ‘green’ or ‘sustainable’ streetscape designs are increasingly evident in the policy and planning literature. However objectives are vaguely defined, integrated quantitative emissions data on street design is relatively unavailable and integrated modelling in street environments is largely absent. Most of the CO2 research literature on street environments has been undertaken within specialised disciplines such as engineering, arboriculture and climatology. Few studies have drawn together the natural and constructed features for streets or tested design modifications that could mitigate CO2. The absence of data on street design and CO2 performance makes it difficult to define appropriate targets and evaluate policy ambitions that seek to face the problem of climate change. The research draws together different street components and layouts to evaluate the CO2 emissions profile and abatement potential for residential streets in Sydney, Australia. The method developed an integrated CO2 emissions model based on its current physical layout and operational use. The street’s constructed elements including kerbs, carriageways, lanes, parking bays were combined with the street’s natural elements, specifically street trees. Sequestration and shading performance for a range of street tree species was estimated using a combination of new and existing modelling techniques including terrestrial laser scanning and climate housing simulation software. Simulations of street retrofit scenarios and new street designs were developed and evaluated. Streets, as relatively stable components of urban form, and as essential functional entities spanning large areas offer substantial mitigation potential. The results showed that dramatic increases in CO2 abatement could be achieved through minor street design modifications. Street retrofits that relied solely on modifications to street trees could achieve almost 7 times more CO2 abatement than a standard street design and 10 times more CO2 abatement when modest design changes were adopted into new street layouts. Opportunities for implementation in policy have been developed in recognition of the complicated management and ownership context of streets. Fundamental obstacles to implementation are also identified. Consistent comparable data that can leverage the optimum climate mitigation and adaptation benefits from these urban forms represents a new opportunity for research and practice. This study lays the basis for design professionals and authorities to test and calculate optimum street configurations and allows governments to make informed decisions, set targets and measure outcomes for these essential public assets.