Developing climate change adaptation strategies: a risk assessment and planning tool for urban heat islands in montreal.
City planning (Environmental aspects)
Acclimatization (Social aspects)
Richardson, Gregory R. A.
Chan, Chee F.
|Publication:||Name: Canadian Journal of Urban Research Publisher: Institute of Urban Studies Audience: Academic Format: Magazine/Journal Subject: Social sciences Copyright: COPYRIGHT 2009 Institute of Urban Studies ISSN: 1188-3774|
|Issue:||Date: Summer, 2009 Source Volume: 18 Source Issue: 1|
|Topic:||Event Code: 290 Public affairs|
|Product:||Product Code: 9107130 Urban Planning Assistance NAICS Code: 92512 Administration of Urban Planning and Community and Rural Development|
|Geographic:||Geographic Scope: Canada Geographic Name: Montreal, Quebec; Montreal, Quebec Geographic Code: 1CANA Canada|
Adapting to climate change is a major concern in cities across Canada. As the climate changes, scientists project more pronounced urban heat island (UHI) effects, potentially resulting in increased human mortality and disease, air pollution, energy consumption, and infrastructure deterioration. To date, few peer-reviewed articles have focused on how to develop and implement evaluative tools and policies for adapting to UHIs in Canada. The purpose of this paper is to help fill that gap. We propose a two-part approach to developing UHI adaptation strategies: first, evaluate and map the risk to human health, and second develop site specific actions for those areas most at risk. The island of Montreal was chosen as the case study. Using a risk based resource allocation methodology we first identified residential areas on the island where UHI exposure and vulnerability are most pronounced. We then conducted a block-level site analysis, followed by a proposed adaptation strategy for Saint Michel, a Montreal neighbourhood with a high UHI risk rating.
Key words: climate change; adaptation; urban planning; Montreal; human health
L'adaptation aux changements climatiques est devenue une preoccupation majeure dans les villes canadiennes. Face a ces changements, les scientifiques predisent une intensification des ilots thermiques urbains. Ceci pourrait concourir a une augmentation de maladies, du taux de mortalite, de pollution atmospherique, de consommation d'energie ainsi qu'a une degradation des infrastructures. A ce jour, peu d'etudes revues par les pairs ont ete publiees sur le developpement et l'implantation d'outils d'evaluation ou de politiques vis-a-vis de l'adaptation aux effets nefastes d'ilots thermiques urbains au Canada. Le but de cet article est d'essayer de combler cette lacune. Nous proposons une approche en deux parties afin de developper une strategie d'adaptation: d'abord evaluer et localiser les risques pour la sante humaine, et ensuite, elaborer des interventions propres aux endroits les plus a risque. L'ile de Montreal a ete choisie pour l'etude de cas. A l'aide d'une methodologie fondee sur l'octroi des ressources en fonction des risques, nous avons identifie des milieux de vie sur l'ile ou l'effet d'ilots thermiques urbains ainsi que la vulnerabilite humaine etaient les plus prononces. Cette analyse a revele que plusieurs quartiers montrealais, dont celui de Saint Michel, presentaient des risques eleves aux effets nefastes des ilots thermiques urbains. Nous avons alors effectue une analyse a l'echelle d'un pate de maisons a Saint Michel afin d'elaborer une strategie d'adaptation locale.
Mots cles: changement climatique; adaptation; urbanisme; Montreal; la sante humaine
Adapting to climate change has become a pressing issue on the policy agenda (Bourque and Simonet 2008; Hasegawa 2004; Lindley et al. 2007; Wilson 2006). In addition to stabilizing atmospheric concentrations of greenhouse gases (climate change mitigation), it is critical that policy makers and planners rapidly develop effective tools for adapting to the meteorological changes already occurring.
Spatial planning "has a critical role to play for mitigating the severity of hazards and for reducing the levels of exposure and vulnerability experienced by the urban system" (Lindley et al. 2007, 544; Wilson 2006). Yet, much of the adaptation research to date has focused on describing the impacts of climate change, rather than on practical planning tools and strategies (Lindley et al. 2006). There are relatively few municipal adaptation plans in force in Canada or internationally, particularly from a spatial planning perspective, although many are under debate (Corburn 2009; Taylor et al. 2006; Wilson 2006).
For Canada's southern regions, where the majority of the population lives, climate change is expected to cause many problems, including a rise in sea levels and more frequent and severe extreme weather such as droughts and heat waves (Lemmen et al. 2008). In this study, we focus solely on the urban heat island (UHI) effect, a problem that is already of concern to urban planners but is expected to be exacerbated due to climate change (Lemmen et al. 2008; McGeehin and Mirabelli 2001).
A UHI occurs when the air temperature in an urban area is higher than in surrounding areas. Dark materials such as pavement or roofing absorb the radiative heat from the sun, raising the local ambient air temperature. Typically, air temperatures in cities are on average 2[degrees]C or more higher than rural areas (Taha 1997), with hotspots within the urbanised area experiencing much higher temperature spikes. In Montreal, for example, localised UHIs of as much as 12[degrees]C above the median temperature have been observed (Oke and Maxwell 1975). UHIs can be studied at multiple geographic scales of analysis (Eliasson 1996; Gallo and Owen 1999; Harlan et al. 2006). At the regional scale, the entire urbanized area may constitute a single UHI. At the citywide scale, zones where large industrial and commercial uses predominate may be much hotter than others. At the city block scale, a large parking lot may constitute a UHI when compared to nearby houses with shady front yards (Taha 1997). In this study, the UHI phenomenon was examined at the city and block scales of analysis.
UHIs are a policy concern for several reasons including poor air quality, increased energy consumption and infrastructure deterioration (Goldberg et al. 2001; Rosenfeld et al. 1998; Smoyer-Tomic et al. 2003; Stone 2005). However, it is the threat that extreme temperatures pose to human health that may be the most serious concern (McGeehin and Mirabelli 2001; McMichael et al. 2006). UHIs can lead to significant increases in human mortality and disease, particularly during a prolonged heat wave. According to Smoyer-Tomic et al. (2003, 468):
During the 2003 heat wave in France thousands of people were hospitalized and 15,000 people died prematurely (Fouillet et al. 2006). Similarly, in Chicago in 1995, extreme heat coupled with high humidity levels, low wind speeds, poor building conditions and other social vulnerabilities, led to the death of 525 people (Klinenberg 1999).
Clearly, Canadian planners must develop effective ways to identify areas of high UHI risk and implement appropriate adaptation measures. The purpose of this study is to develop and implement evaluative tools and policies for adapting to UHIs in Canada. A two-part approach was used to develop a UHI adaptation strategy for the case study site--the island of Montreal. First, the magnitude and geographic location of UHI risk was mapped across the study area. Second, a program of policies and actions to reduce UHI risk in one neighbourhood was developed. The approach used was based on long established risk assessment methodologies for managing threats to human health from natural and other hazards (Lindley et al. 2006; Slovic et al. 1979). The results of the study highlight the importance of collaboration among various disciplines including planners, climate scientists and public health specialists, and the need for risk management strategies that respond effectively to highly variable local conditions.
The risk to human health from UHIs can be understood as comprising at least three elements: (1) the physical occurrence of a UHI, (2) the exposure of the population to the event, and (3) the extent of vulnerability of those exposed (Lindley et al. 2006). This suggests three key areas of inquiry and analysis for planners: How do UHIs form and what can be done to reduce their frequency and severity? What measures may be used to keep people away from areas prone to dangerous UHIs? What factors contribute to human vulnerability to heat and what can be done to fortify people's ability to withstand heat stress?
Four principal causes for the occurrence of UHIs have been identified (Watkins et al. 2007). They are lack of vegetation, low reflectivity of surfaces (low albedo), high thermal mass of buildings and high waste heat production. Plants, especially trees, cool the air through shading and the process of evapotranspiration. Urban districts with little vegetation are deprived of this cooling effect (Gill et al. 2007; Oke et al. 1989). Roofing and paving materials (e.g. tar, gravel, and asphalt) are major contributors to UHI as these dark materials absorb the surfs energy more readily than lighter-coloured surfaces. With regard to buildings, their size, proximity and heat-storing capacity can cause large amounts of heat to be trapped during the day, to be released slowly throughout the night (Oke et al. 1991; Ghiaus et al. 2006; Watkins et al. 2007). Finally, heat generated from the combustion of fuels, industrial activities and air conditioning, known as waste heat, can increase air temperatures (Oke et al. 1991; Taha 1997; Wilhelmi et al. 2004).
Certain climate conditions and microclimate effects, such as high humidity levels and low wind speed, can aggravate UHIs (Watkins et al. 2007). Furthermore, the extent and severity of a UHI are highly localized (Oke 1981; Taha 1997; Rosenzweig et al. 2006). Rosenzweig et al. (2006) found that the cooling effect of New York's large Central Park extends no more than 60 metres beyond its boundaries. Since wind can have a moderating effect on air temperature, the most serious threats to human health from extreme heat arise in calm conditions (Kalkstein and Greene 1997).
Whenever UHIs do occur, the number of people exposed and the duration and severity of their exposure may depend on a number of physical as well as social factors. For example, the lack of ventilation and proper insulation in some apartment buildings may expose residents to dangerous levels of heat. As hot air rises, this may be especially true on the top floors of high-rises (Klinenberg 1999). Exposure may also increase if occupants are deprived of access to cool places nearby: a shady yard, a public pool, or a well ventilated common area. Finally, fear of crime and social marginalization may increase exposure if residents are afraid to leave their apartment or even open their windows for increased ventilation (Klinenberg 1999; McGeehin and Mirabelli 2001; Watkins et al. 2007).
Not everyone exposed to extreme heat will be similarly affected. Human vulnerability to UHIs is exacerbated by air pollution and poor health. Accordingly, groups particularly exposed and vulnerable to UHIs include low income earners who may lack access to the best health care, the sick, the very young, the elderly, and people living in areas with high air pollution (Buechley et al. 1972; Lindley et al. 2006; Patz et al. 2000; Vandentorren et al. 2006). Moreover, residents of cities in temperate climates may be more vulnerable to extreme heat conditions. Lack of regular exposure to heat is believed to limit the adaptive capacity of residents, leading to higher vulnerability (McGeehin and Mirabelli 2001).
UHI Adaptation Measures
Planners from cities across North America and Europe have documented numerous strategies for reducing the occurrence of UHIs and the extent of human suffering from heat waves. Possible UHI adaptation strategies include planting trees, creating more green spaces, installing green roofs, and erecting living walls (Gill et al. 2007; Oke et al. 1989). To increase albedo, cities have encouraged the use of light paving materials and special white paints for roofs (white roofs) (Taha 1997). Climate sensitive design and materials can help reduce the thermal mass of buildings (Ghiaus et al. 2006; Watkins et al. 2007). Urban design studies have focused on the size of lots in new subdivisions, and the size, location and arrangement of buildings within lots (Stone 2005). In addition, waste heat reduction may be accomplished through more efficient appliances, building energy retrofits and anti-idling bylaws among other measures. Table 1 provides a summary of measures for reducing UHIs at the local level.
The island of Montreal, which for our purposes is typical of large North American cities with a temperate climate, was chosen as the subject of this study. The island, with a population of approximately 1.9 million people (Statistics Canada 2001), experiences an average daily high temperature of 26.2[degrees]C and an average daily low of 15.6[degrees]C in the month of July, the warmest month of the year (Environment Canada 2009). It is projected that due to climate change Montreal will experience more frequent intense heat days and a stronger UHI effect (Bourque and Simonet 2008). Unlike cities with warmer climates, Montreal's population is not regularly exposed to heat, and thus may have lower adaptive capacity to extreme heat events (McGeehin and Mirabelli 2001). Bourque and Simonet (2007, 202) for example, state "in Quebec, the anticipated rise in mean temperatures [from climate change] may lead to an increase in annual mortality rates." The predicted increase in extreme heat days and the potential consequences for the health of Montreal residents, make the island a good choice for this study.
Figure 1 shows the relationship between UHI and land use: high temperatures can be seen in zones occupied predominantly by large scale commercial and industrial uses. This confirms the finding that urban areas which are characterized by large buildings and dark surfaces produce strong UHI effects (Taha 1997). However, since few people live in large scale commercial and industrial zones, the risk of exposure by vulnerable populations may be reduced. Still, a major concern may be those vulnerable groups often residing in close proximity to the industrial and commercial areas. The severe UHIs may affect them as they travel through, work, or shop in these areas. Also, homeless individuals who stay in these areas may face severe risk.
[FIGURE 1 OMITTED]
As shown in the areas marked A and B, large scale commercial and industrial zones appear to have the highest temperatures.
By comparison, the UHIs in the central, residential areas of the island of Montreal are not as extreme as in the industrial sectors. However, because the central areas of Montreal are densely populated and have high proportions of vulnerable populations, as well as high temperatures, we find that many vulnerable groups are still exposed to significant UHIs. These observations underscore the need to incorporate social data in analyzing UHI risk.
In order to select appropriate adaptation measures for Montreal, we applied a two-step approach. First, with the use of a geographic information system (GIS)based tool, we created a UHI risk map for the island of Montreal by combining air temperature data and selected demographic data. This map helped us to locate those areas that are prone to more severe UHIs and that are also inhabited by populations particularly vulnerable to excessive heat. Second, Saint Michel, a neighbourhood with a high UHI risk rating, was studied in greater detail to determine the causes of local UHIs and identify ways to reduce occurrence, exposures and vulnerabilities. This micro-scale case study provides an example of how to conduct a neighbourhood specific UHI adaptation strategy.
Mapping UHI Risk to Human Health on the Island of Montreal
A UHI risk map for the island of Montreal was prepared with a GIS tool, and a methodology adapted from Lindley et al. (2006) (Figure 2). An air temperature data layer (2) was overlaid with three human vulnerability data layers (3): the density of people living in poverty, children under the age of five and adults over 65, and people over 65 living alone. The values for each data layer were combined to produce UHI risk ratings for each geographic unit (4). Figure 3 shows a map of these UHI risk ratings for the centre of the island of Montreal, where the risk is more pronounced. The map can be used to easily identify areas of highest risk to UHI and allocate resources accordingly.
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
Detailed Analysis of the Saint Michel Neighbourhood
An examination of the UHI risk map (Figure 3) showed several sites that were good candidates for detailed study. These areas constituted significant heat islands and had relatively high concentrations of vulnerable populations. Among these areas, we selected Saint Michel (Figure 4). Saint Michel's built form resembles the typical Montreal urban fabric with long and narrow blocks of row housing of between two and four storeys, and a mix of land uses. Thus, the adaptation measures developed for this site can serve as a demonstration for other similar morphologies in Montreal. Figure 4 shows the boundaries of the study area and the levels of risk to UHI.
Saint Michel is a densely populated area with a total population of 19,350 residents (Statistics Canada 2001). It has a large proportion of low income families and an average annual income of $34,927, which is 71% of the Montreal average. A large proportion of residents live in poverty: 41% of the population lives under Statistics Canada's low income cut-off, compared to 29% for Montreal (Statistics Canada 2001). In addition, several of the hottest UHIs on the island dot the neighbourhood (Figure 4). As noted earlier, the very young and the very old are particularly vulnerable to UHIs. In Saint Michel 20% of the population is below the age of five or over 65 (Statistics Canada 2001).
[FIGURE 4 OMITTED]
UHI Intensity by Block Type
After selecting the Saint Michel site, a detailed block analysis was conducted in order to find the causes of UHI at the micro-scale. For this analysis the study area's urban form was divided into seven typical block types. Each block type was defined by its most prevalent built form and use. Block types included the following:
* Industrial and light manufacturing;
* large scale commercial and institutional;
* multi-unit attached residential (narrow block and wide block);
* mixed residential and commercial;
* single-unit detached residential; and
* green space.
Various physical characteristics of each block were examined, including the number of stories of a typical building, the nature of front and back yard uses (e.g., gardens, paved driveways), the building footprints, and the prevalence of trees. Finally, the temperature map was studied to identify differences in UHI intensity from block to block. For each of these types, we identified the physical characteristics of the built form and produced a figure showing the different surface types. An example of this type of analysis showing the area covered by vegetation and various surface types can be seen in Figure 5.
[FIGURE 5 OMITTED]
Several key findings from this block type analysis are notable. The built form on this site has a significant effect on UHI intensity. Block types with one or more of the following attributes--mineralized surfaces (low albedo), less vegetation (biomass) and larger buildings (thermal mass)--generally experience more intense UHIs. This finding is clearly demonstrated in Figure 6, where three of the block types are overlaid onto a temperature map of Saint Michel. Figure 6 suggests that a lack of biomass contributes to UHIs in several residential blocks. For example, in zone A, where there are more trees than in zones B or C, lower temperatures are found. Areas with higher percentages of impermeable, low-albedo surfaces (e.g., dark coloured pavement and roofs)--demarcated in Figure 6 by zones B (high density residential) and C (industrial)--experience higher temperatures.
Reducing UHI Occurrence, Exposure and Vulnerability in Saint Michel
As noted above, the findings from the block type analysis showed that the built format the microscale has an important impact on UHI intensity. Therefore, any strategy should be based on targeting vulnerable populations at the neighbourhood scale. In this section we recommend a strategy for reducing UHI risk in Saint Michel. These recommendations are grounded on four guiding principles, which were developed by the authors based on best practices from the literature (Gill et al. 2007; Lindley et al. 2007; Watkins et al. 2007).
1. Give priority to residential areas facing the greatest risk;
2. Engage all stakeholders in a long-term 'Cool Saint Michel' campaign;
3. Create a new cool site with every new construction; and
4. Implement cooling measures for street corridors.
[FIGURE 6 OMITTED]
As the causes and effects of UHIs are highly localized, the recommendations for UHI risk reduction in Saint Michel were tailored for each one of the seven representative block types found there. Consideration was given to relevant physical and socioeconomic characteristics of each block type (Chan et al. 2007). A summary of these measures is included in Table 2.
For example, one key recommendation was the planting, preservation and maintenance of trees throughout Saint Michel, on both public and private property. One difficulty in implementing this strategy is the very limited space available along certain streets. In these areas, we recommend narrowing the paved roads to create wider front yards or wider sidewalks to accommodate trees. On the other hand, wide streets may be necessary in Saint Michel's industrial sector to accommodate the movement of trucks. In addition, industrial buildings occupy a large percentage of a block's surface area. Consequently, there is little or no available space for planting trees and we mainly focused industrial zone interventions on the choice of roofing material.
Several blocks contain paved back alleys which are public rights of way. "Ihese alleys, which have no garages or driveways adjoining them and are not cleared of snow in winter, appeared to have little practical use apart from summer play space. These alleys offer excellent opportunities for significant greening of the neighbourhood, through a mix of private and public planting and maintenance efforts.
In addition, we urge a careful evaluation of UHI impacts as part of the environmental assessment of any significant new development. Finally, dark roofing material on residential and industrial buildings contributes significantly to the local UHI effect. We therefore recommend that when existing roofs are replaced, landlords install a white roof. White roofs are more appropriate than green roofs for lower-income residential areas such as Saint Michel because they are cheaper to install and do not require the addition of structural reinforcements to existing buildings.
Case Study Discussion
A number of lessons can be learned from this case study. While the work presented is specifically focused on Montreal, the following points may also be applicable to cities developing UHI and other climate change adaptation strategies.
First, it is important to recognize that UHIs are a local phenomenon (Oke 1981; Watkins et al. 2007). Accordingly, UHI adaptation strategies should be neighbourhood specific, responding to local physical, demographic, and socioeconomic characteristics. For example, as noted earlier, the cooling effect of a large park is limited (Rosenzweig et al. 2006). Therefore, UHIs cannot be alleviated by a series of neighbourhood parks; rather, interventions at the level of streets and buildings are necessary.
Second, there is a clear need for more and better data in order to assess UHIs and measure the relative temperature reduction potential of different strategies. The temperature data used in this study is only a rough approximation of the air temperature as it is perceived by people on the ground. A better measure of air temperature that accounts for humidity, wind speed, shading, and the effects of built form would paint a more precise picture of the location of UHIs. In addition, more information about the factors that make people vulnerable to UHIs and their relative importance, are needed.
To help policy makers discern between competing alternatives, the costs and benefits of various alternatives need to be considered, including their impacts ancillary to the UHI phenomenon. Perhaps the most obvious example is tree planting. Trees require a decades long and potentially costly commitment to maintenance and care (McPherson 1992). They can also interfere with utility distribution lines and other infrastructure such as sidewalks and building foundations (McPherson 2000). Conversely, trees reduce the occurrence of UHIs by providing shade and evaporative cooling. Furthermore, they perform a great number of other ecological services such as improving air quality, retaining storm water runoff, preventing erosion, and reducing noise. Finally, they add aesthetic, recreational and economic value to neighbourhoods. All these varied costs and benefits should be considered when selecting UHI adaptation measures (City of Montreal 2005).
In addition, when deciding among UHI reduction strategies it is important to include future climate change and urban development scenarios, as well as socio-demographic projections. Examples of this type of modelling exist (Coutts et al. 2008; Gill et al. 2007). In a study modelling green cover and its impact on UHI in Manchester, UK, Gill et al. (2007) found that a ten percent addition in green space in downtown and high density residential areas would keep temperatures at or below 1961 to 1991 baseline levels, thus masking the predicted warming effect due to climate change until 2080. A similar study, including the cost of various green space options, should be conducted for Montreal.
Third, while this report focuses on physical interventions, addressing human vulnerabilities directly presents another major avenue for UHI adaptation. We note that the definition of risk adopted here includes indicators of social vulnerability, q-he needs of places like Saint Michel are acute in many respects other than UHI risk. UHI adaptation measures that address numerous issues should be considered in order to achieve the greatest risk reduction given limited resources. Interventions, for example, could include improved health and social services and education campaigns about climate change.
Fourth, in carrying out this study, we collaborated with geographers, health specialists, planners, and experts in other fields. It is clear that further progress toward tackling UHI risk requires ongoing collaboration between many different disciplines (Corburn 2009). For cities, it is important that various departments coordinate their work to avoid diverging goals, unnecessary conflict and the waste of scarce resources. For planners, effective adaptation will require a good understanding of complex scientific concepts. This is especially important as planners will need to explain these concepts to a public facing serious threats and possibly conflicting objectives. Ultimately, an engaged public and close interdisciplinary collaboration will be key for a successful adaptation strategy.
Lastly, while in this report we have focused on climate change adaptation, this by no means suggests policy makers should ignore climate change mitigation. Broadening the agenda on climate change to include adaptation not only helps to reduce human suffering but also builds awareness of the consequences of climate change, thus building support for mitigation. Further, integrating mitigation and adaptation efforts can lead to more effective, more efficient policies. It also would help avoid counterproductive or mal-adaptive responses which may reduce human suffering in the short term, but in so doing increase green house gas emissions. It is for this reason, for example, that in Saint Michel we did hOt recommended the installation of air conditioners, which are energy intensive. Rather, many of the recommendations--such as tree planting, the greening of alleyways, and the installation of white roofs in fact also can mitigate climate change. Both mitigation and adaptation strategies should be integrated and pursued in tandem.
Conclusions and Recommendations
The severity of the UHI threat to human health is considerable and is likely to intensify as the climate changes. Some adaptation measures may be beyond the jurisdiction of local officials. However, many aspects of the physical urban environment contribute to UHI risk and are subject to local control. These include the paving of surfaces, vegetation coverage, the size and placement of buildings, and the materials used to build them.
A GIS based tool, as employed in this study, can be valuable for mapping UHI risk. GIS software is able to display complex data clearly, easily combines multiple data sets, and allows ongoing refinement as data layers (air temperature, demographic and health factors) are updated. Also, this GIS based methodology provides a means for planners to collaborate with professionals from other disciplines in the development of such data.
Based on our experience with this study we recommend a multi-step policy making approach to developing an adaptation strategy, as follows:
1. Focus UHI Adaptation Efforts on Neighbourhoods Most at Risk UHI adaptation efforts and resources should be targeted primarily to those areas in a city or region where the most exposed and most vulnerable populations reside. This can be achieved by using a GIS risk-based allocation methodology similar to the one used in this study. Since UHI events and impacts are highly localized as demonstrated in the Saint Michel case study, most of the resources and efforts should be devoted to developing and implementing site-specific policies and programs.
2. Assess Conditions at the Micro-Scale to Determine the Causes of Local UHIs
It is important to study the interplay of existing land uses, vegetation and open areas, built form and other physical characteristics at the local scale to identify the principal contributing factors to the UHI. An examination of planned land use changes correlated with future climate change scenarios can illustrate the impact of such land use changes. This analysis is useful because it provides clues to what may be the most practical and effective solutions to a particular UHI scenario.
3. Identify Potential Adaptation Measures to Reduie Local UHI Risk Not all UHI adaptation measures are equally suitable for all areas. For instance, in a low-income area such as Saint Michel, the relatively high costs of green roofs will likely make them too expensive for most home owners (even if subsidized). Thus, a first and critical step for considering UHI adaptation strategies is determining which measures make sense in the given area. A short list of potential strategies should be developed, including only those that are deemed most feasible considering the area's physical and socioeconomic conditions and trends.
4. Select Adaptation Measures Most Effective and Appropriate for the Area Once a shortlist of possible UHI adaptation strategies has been identified, evaluate the temperature reduction potential of each alternative and determine those that will have the greatest impact. The potential cooling impacts maybe modelled using GIS (Gill et al. 2007). When evaluating and selecting from the various alternatives, it is important to consider all costs and benefits, including those that are ancillary to the UHI phenomenon. For example, with tree planting, policy makers should consider not only the costs of planting and maintaining trees, but also the various ecological, aesthetic, recreational and economic benefits.
For policy makers, the overarching objective should be to implement those measures that deliver the greatest cooling benefit at the lowest cost, while considering local values and existing social, physical and economic conditions. While the approach proposed here focuses specifically on UHIs, the overall direction and many points are believed to be valid and suitable for other climate change adaptation issues.
We would like to thank Professor Yves Baudouin of the Department of Geography of the Universite du Quebec a Montreal for permission to use the temperature data used in developing out UHI risk map. Thank you to Professors Jeanne Wolfe, Main Trudeau and David Brown, our academic advisors at the McGill School of Urban Planning, for guiding us through the research process and providing discerning questions and observations. Finally, we would like to recognize Herve Loge at the City of Montreal for his valuable input, the Canadian Institute of Planners for providing us with partial funding for this project, and the editorial team and anonymous reviewers at the Canadian Planning and Policy--Amenagement et politique au Canada for their constructive comments.
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Gregory R.A. Richardson
and Chee F. Chan
School of Urban Planning
(1) This study was carried out as part of a studio class by four McGill University graduate urban planning students in the fall of 2007. Each of the authors participated equally in the project.
(2) This data was produced and interpreted by a team led by Professor Yves Baudouin of the Department of Geography at the Universite du Quebec a Montreal. This temperature map has a resolution of 30m x 30m, and was taken at 10:30 am on June 27, 2005, a day when cloud cover and wind speed were not significant. The data is limited to 10:30 am because this is when the satellite passes over Montreal. The temperatures shown on the map are the interpretation of the absorbance, storage, and reflectance of solar radiation of the surface materials. These temperatures represent air temperatures just above the ground. However, we use this air temperature as a good first approximation of the actual air temperature as perceived by people. Then, a numerical rating from one to four, representing low to high heat hazard, was assigned to all the areas with temperatures above the average.
(3) Re human vulnerability layer is composed of three characteristics that make people more vulnerable to extreme heat: being less than five or over 65 years of age, living on a low income, and being over 65 and living alone. Data for this layer comes from the 2001 Canadian Census at the dissemination area (Da) level of analysis. The density of each vulnerable group is calculated for each Da, and then given a score of one to four, representing low to severe vulnerability. Then, the three scores for each Da are averaged to yield a composite vulnerability index. This weighting system was chosen for its simplicity.
(4) In the final step of this methodology, the hazard and vulnerability layers are averaged to give a final risk index from one to four. Equal weighting was given to the two data layers.
Heat stress events adversely affect both human health and human behaviour ... Heat events can directly affect morbidity through heat cramps, heat exhaustion, and non-fatal heatstroke; and, mortality through heatstroke. Physiological stresses include dehydration, fatigue and a reduced ability to perspire or cool the body...Indirect heat effects include increased risk of death from cardiovascular disease, cerebrovascular accidents and vascular lesions, respiratory diseases, and increased susceptibility to infectious diseases... Heat stress exacerbates many underlying health conditions.
Table 1: A Summary of UHI Adaptation Measures That Can be Implemented at the Local Level Strategies Actions Increase biomass Preserving existing trees and planting more trees in the city * Inventory of all trees in public streets and spaces * Tree planting programs (municipal, NGO and private sector) * Landscape ordinances that require certain percentage of tree coverage in new developments/parking lots * Bylaws preventing the felling of existing trees Preserving existing green spaces and creating new ones * Open space impact fee ordinances requiring developers of new residential properties to pay a fee or contribute a proportionate share of open space * Zoning regulations to restrict expansions of residential buildings into rear courtyards * City-financed green roof subsidies * Green roof demonstration projects on municipal buildings Increase surface Installing cool or white roofs albedo * Education and outreach program for developers and general public * Technical research of local building standards and monitoring * Grant programs to help homeowners/businesses install roof retrofits Increasing ground albedo * Paving guidelines to assist municipalities and developers with appropriate use of materials and design * Strategy for de-paving alleys Increase thermal * Modify existing cool-weather building performance of retrofit assistance programs for all season built form performance * Regulate improved building design and materials through the building code (i.e. porous paving stones, higher albedo surfaces) * Climate sensitive urban design and planning (i.e. master plan, sustainable development plan) Reduce exposure * Installation of air conditioning and/or and vulnerability passive cooling techniques * Access to cool places (schools, libraries and pools) * Preventative health care programs promoting healthy active lifestyles Respond to heat Comprehensive plan designed to save lives wave emergencies during heat waves * Heat health alert system to predict days where extreme heat is dangerous * Response strategy to coordinate the actions of public agencies and non-governmental partners * Universal access to medical facilities Reduce waste heat * Vehicle anti-idling bylaws * Building energy retrofits and energy efficient appliances * Regulation of large emitters Sources: Gill et al. (2007); Kosatsky et al. (2005); Lindley et al. (2007); Rosenfeld et al. (1998). Table 2: Key UHI Adaptation Measures * Increase biomass through tree planting, green space creation and preservation, green roofs, and living walls * Reduce paved surfaces by narrowing paved roads and greening alleyways * Increase albedo of roof and ground surfaces, including driveways and sidewalks * Improve thermal performance of buildings and urban form through climate sensitive design and materials * Reduce waste heat with anti-idling bylaws, building energy retrofits and energy efficient appliances
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