louisville heat mgt report_public comment april 2016

8/18/2019 Louisville Heat Mgt Report_Public Comment April 2016

1/109Louisville Urban Heat Management Study 1

Louisville

Urban Heat Management Study

April 2016 Draft for Public Comment



Executive SummaryCommissioned by the Louisville Metro Ofce of Sustainability, this

study is the rst comprehensive heat management assessment

undertaken by a major US city and constitutes one component of a

broader effort to enhance livability, health, and sustainability in the

Louisville Metro region. Through this report, we assess the extentto which Louisville Metro is warming due to urban development

and deforestation, estimate the extent to which rising temperatures

are impacting public health, and present a series of neighbor -

hood-based recommendations for moderating this pace of warming.

The study is presented in ve sections, through which we rst

provide an overview of the science of the urban heat island

phenomenon, its implications for human health, and how urban

temperatures can be moderated through urban design and other

regional strategies. The study next presents our methodology for

estimating the potential benets of specic heat managementstrategies for lowering temperatures across Louisville and lowering

the risk of heat of illness during periods of extreme heat. The third

and fourth sections of the report present the results of our heat

management assessment and include neighborhood-specic

ndings on the potential for lessened heat risk through the adoption

of cool materials, vegetative, and energy efciency strategies. The

nal section of the report presents a set of metro-wide and

neighborhood-level recommendations for managing Louisville’s

rising heat risk, which include the following:

1. Cool materials strategies should be prioritized in industrial and

commercial zones exhibiting extensive impervious cover with

limited opportunities for cost-effective vegetation enhancement.

2. Tree planting and other vegetative strategies should be

prioritized in residential zones, where population exposures to heat

are greatest and lower-cost planting opportunities are found.

3. Energy efciency programs consistent with the Louisville Climate

Action Report and Sustain Louisville should be expanded and

integrated with urban heat management planning.

4. Some combination of heat management strategies should be

undertaken in every zone targeted for heat adaptation planning.

5. A combination of new regulatory and economic incentive

programs will be needed to bring about the land cover changes and

energy efciency outcomes modeled through this study.



AcknowledgementsWe are grateful to the Louisville Metro Ofce of Sustainability, the

Augusta Brown Holland Philanthropic Foundation, and the OwsleyBrown Charitable Foundation for sponsoring this study, the rstcomprehensive assessment of urban heat management in the

United States.

This study would not have been possible without the contribution ofdata and expertise from several regional agencies, including theLouisville Metro Ofce of Sustainability, the Louisville Metro AirPollution Control District, and the Louisville/Jefferson CountyInformation Consortium. A special thanks to Maria Koetter,Director of the Ofce of Sustainability, and Michelle King, Executive

Administrator of the Air Pollution Control District, for assisting in thedesign and management of this study. Thanks also to the LouisvilleTree Advisory Board for helping to educate the public on the critical

importance of tree canopy for the region’s environmental and publichealth.

This report is a result of a collaborative project between the

School of City and Regional Planning and the School of Civil and

Environmental Engineering at the Georgia Institute of Technology.

Professors Brian Stone and Armistead Russel co-directed the

study. Peng Liu and Kevin Lanza carried out key elements of the

project’s modeling, analysis, and mapping components. Special

thanks to Dr. Bumseok Chun and Dr. Jason Vargo for serving

as consultants on the land surface inventory and health impact

analysis components of the study. Thanks also to Jessica Brandonfor handling the graphic design and layout components of the

report.

A nal and hearty thanks to the many residents of Louisville who

have attended public meetings and presentations on this work

and who will be the key force for achieving a cooler and more

sustainable Louisville.


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Louisville Urban Heat Management Study 4

Contents

Section 1: Introduction 5

Section 2: Heat Management Scenarios 19

Section 3: Heat Scenario Results 29

Section 4: Population Vulnerability Assessment 51

Section 5: Heat Management Recommendations 59

Appendix A: District Findings & Recommendations 74

Appendix B: Cited References 105


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Heat in the River CityDowntown Louisville, where summer afternoon

temperatures are much higher than in the surrounding countryside.



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1 Introductiono drive east on River Road rom DowntownLouisville on a hot summer afernoon is totransition not only through a rapidly changing

built environment – rom skyscrapers toindustrial acilities to neighborhoods –but through a rapidly changing climaticenvironment as well. Cities have long beenknown to exhibit higher temperatures than thesurrounding countryside, at times in excesso 10°F, due to the intensity o heat-absorbingmaterials in their downtown districts and therelative sparseness o tree canopy and other vegetative cover, which provides evaporativecooling and shading.



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Known technically as the “urban heat islandeffect,” the heating o the urban landscapethrough development is urther acceleratingthe rate at which cities are warming due tothe global greenhouse effect, with increasingimplications or public health and criticalinrastructure ailure.

Trough this report, we assess the extentto which the Louisville Metro regionis warming due to urban developmentand deorestation, estimate the extent towhich rising temperatures are impactingpublic health, and present a series oneighborhood-based recommendationsor moderating this pace o warming.Commissioned by the Louisville MetroOffice o Sustainability, this study represents

the first comprehensive heat managementassessment undertaken by a major US cityand constitutes one component o a broadereffort to enhance livability, health, andsustainability in the Louisville Metro region.

Tis report is structured as five sections.In this first section, we provide anoverview o the science o the urban heatisland phenomenon, its implicationsor human health and quality o lie in

cities, and how urban temperatures canbe moderated through urban design andother regional strategies. Te reportnext presents our study methodology orestimating the potential benefits o specificheat management strategies or loweringtemperatures across Louisville and loweringthe risk o heat o illness during periodso extreme heat. Te third and ourthsections o the report present the resultso our heat management assessment andinclude neighborhood-specific findingson the potential or lessened heat riskthrough the adoption o cool materials, vegetative, and energy efficiency strategies.Te final section o the report presents aset o county-wide and neighborhood-levelrecommendations or managing Louisville’srising heat risk and outlines additional stepsneeded to support the development o heat

adaptation policies.

1.1 Climate Change in Cities

Climate change in cities is driven by twodistinct phenomena, one operating atthe scale o the planet as a whole and the

other operating at the scale o cities andregions. Te global greenhouse effect isa climate phenomenon through whichthe presence o “greenhouse gases” inthe Earth’s atmosphere traps outgoingradiant energy and thereby warms theatmosphere (Figure 1.1). A natural warmingmechanism, without the operation o aglobal greenhouse effect the temperatureo the Earth would approximate that o theMoon, rendering the planet inhospitable to

lie. Since the beginnings o the IndustrialRevolution, increasing emissions o carbondioxide and other greenhouse gases haveserved to enhance the natural greenhouseeffect, leading to an increase in globaltemperatures over time. Tis global scalewarming phenomenon has resulted in anaverage increase in temperatures acrossthe United States o about 1.5 to 2°F overthe last century, an extent o warmingexperienced in both urban and rural

environments [1].

In addition to changes in the compositiono the global atmosphere, changes in landuse at the scale o cities also contribute torising temperatures. Known as the urbanheat island (UHI) effect, the displacemento trees and other natural vegetationby the construction materials o urbandevelopment increases the amount o heatenergy that is absorbed rom the Sun and

stored in urban materials, such as concrete,asphalt, and roofing shingle. Four specificchanges in urban environments drivethe urban heat island effect, including:1) the loss o natural vegetation; 2) theintroduction o urban constructionmaterials that are more efficient atabsorbing and storing thermal energy thanthe natural landscape; 3) high density urbanmorphology that traps solar radiation; and


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4) the emission o waste heat rom buildingsand vehicles.

As illustrated in Figure 1.2, these ourwarming mechanisms in cities elevatethe quantity o thermal energy retainedand emitted into the urban environmentthrough distinct pathways. Te loss o treesand other natural land covers contributesto a warmer environment through areduction in shading and, most importantly,a reduction in evaporative cooling – theprocess through which plants use solarenergy to convert water to water vapor. Aswater is transmitted through plant cells andreleased to the atmosphere as water vapor,heat energy is also transported away romthe land surace in a latent orm that doesnot contribute to rising temperatures atthe surace. As trees and other vegetation

are displaced by urban development,less moisture is retained by the urbanenvironment, resulting in less evaporativecooling.

Compounding the loss o surace moistureis the resuracing o the urban environmentwith the bituminous and mineral-basedmaterials o asphalt, concrete, brick, andstone – materials that contribute to highertemperatures through three mechanisms.First, urban construction materials suchas asphalt are less effective in reflectingaway incoming solar radiation, a physicalproperty known as “albedo.” As thealbedo or reflectivity o cities is loweredthrough urban development, the quantityo incoming solar radiation absorbedand retained is greater. Second, mineral-based materials tend to be more effective

Figure 1.1 The

global greenhouse

effect



is absorbed by the vertical suraces o thecity, more heat is retained in the urbanenvironment.

Lastly, cities are zones o intense energyconsumption in the orm o vehicle usage,the cooling and heating o buildings,and industrial activities. As immensequantities o energy are consumed in urbanenvironments, waste heat is produced thatis ultimately vented to the atmosphere,

contributing to rising temperatures. Insome US cities, waste heat rom energyconsumption has been estimated to accounor about one-third o the UHI effect [2].

Research ocused on the extent to whichthe global greenhouse effect and urbanheat island effect contribute to warmingin large US cities, including Louisville,

in storing solar energy than the naturallandscape – a property that results in theretention and release o heat energy in thelate evening and into the night, keepingurbanized areas warmer than nearby ruralareas. Lastly, urban construction materialssuch as street paving and roofing shingleare generally impervious to water, and thusurther reduce the amount o moisturethat is absorbed and retained in cities orevaporative cooling.

A third physical driver o the UHI effectis the morphology or three-dimensionalcharacter o the urban landscape. Indensely developed downtown districts,tall buildings and street canyons limit theextent to which reflected solar energy romthe surace can pass unimpeded back tothe atmosphere. As this reflected energy

Figure 1.2 Driversof the urban heat

island effect


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adopted in 2014 a cool roofing ordinancedesigned to increase surace reflectivity,thus reducing the quantity o heat energyabsorbed and retained by roofing materials[5]. Seattle, Washington, and Washington,DC, have recently adopted new zoningpolicies establishing minimum greenarea goals or all new development [6,7].

Building on this trend, Louisville Metro hasundertaken comprehensive assessmentso the region’s tree canopy and urban heatisland to lay the groundwork or newpolicies and programs to manage regionalwarming trends, the first major US city todo so.

1.2 Consequences of Rising

Temperatures

With recent warming at both the globaland regional scales projected to continue,the public health threat o heat is anational concern. Te National WeatherService defines a heat wave as two ormore consecutive days o daytime hightemperatures ≥ 105°F and nighttimelow temperatures ≥ 80°F [8]. When airtemperatures rise above the temperatures atwhich people are accustomed, the body may

finds the urban heat island effect to playa more significant role in warming trendssince the 1960s. Figure 1.3 depicts averagetemperature trends in 50 o the largest UScities and in rural areas in close proximityto these cities. What these trends revealis that urban areas not only tend to behotter than rural areas – a maniestation

o the UHI effect – but that the rate owarming over time is higher in urbanareas. In addition, temperature trend datarom large US cities shows that the UHIeffect is a more significant driver o risingtemperatures in cities since the 1960s thanthe global greenhouse effect. For most largecities o the United States, urban zones arewarming at twice the rate o rural zones –and at about twice the rate o the planet as awhole [3].

Such rapid rates o warming have motivatedan increasing number o municipalgovernments to develop heat managementstrategies designed to mitigate the urbanheat island effect. Chicago, Illinois, orexample, has planted over 500,000 trees overthe last 15 years to offset rising temperaturesthrough increased green cover, as well as toincrease moisture retention and minimizeflooding [4]. Los Angeles, Caliornia,

Figure 1.3 Urban and

rural temperature trend

in proximity to 50 large

US cities (1961-2010)


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not be able to effectively shed heat, causinghealth problems. Summertime, when airtemperatures reach an annual high, is theseason o greatest heat-related illness anddeath. In particular, heat waves duringthe beginning o the summer are the mostdangerous because individuals have not yetacclimated to the warmer conditions [9].

Te most serious heat-related illnesses areheat exhaustion and heat stroke. Commoncharacteristics o heat exhaustion includenausea, muscle cramps, atigue, anddizziness. I lef untreated, heat exhaustioncan progress to heat stroke, a more seriouscondition characterized by a core bodytemperature over 103°F and intense nausea,headache, dizziness, and unconsciousness.

I fluids are not replaced and bodytemperature is not reduced in a timelymanner, death can occur [10].

Regarding heat-related mortality, heat caneither be the primary actor, i.e., heat stroke,or the underlying reason. Individuals withpreexisting medical conditions, particularlycardiovascular and respiratory disease, areat higher risk or mortality during periodso high and/or prolonged heat. In a study

o nine counties in Caliornia, each 10°Fincrease in temperature throughout theday corresponded to a 2.3% increase inmortality [11]. Te 1995 Chicago heat wave,which lasted five days in July, resulted inmore than 700 heat-related deaths [12].More troubling was an intense heat wavethat persisted or weeks across Europe andresulted in more than 70,000 heat-relateddeaths over the course o the ull summer[13]. Global and regional temperatureprojections find that intense heat waveswill be ar more common in the comingyears. By the end o the century, researchersproject 150,000 additional heat-relateddeaths among the 40 largest US cities,including Louisville [14].

One consequence o extreme heat relatedto public health is its effect on outdoor

activity. Heat waves can deter outdooractivity by lowering thermal comort levels.Individuals are less likely to participate inoutdoor activities when the weather is toowarm, and those that do may experiencesymptoms o heat illness during periods ohigh temperatures [15]. Tis may have anegative impact on physical activity levels

in the US, a country where one-third oadults and almost one-fifh o children areobese [16]. Extreme heat may also influencethe work schedules o those in outdooroccupations, such as construction, asoutside exertion during peak heat levels canbe unhealthy [17].

Not all members o a community areequally affected by extreme heat. Te ends

o the age spectrum, i.e., the young andthe old, are most vulnerable to heat wavesdue to lower physiological capabilities toregulate heat and a lack o mobility. Tesick are vulnerable to elevated temperaturesbecause o relatively weak immune systemscompared to healthy adults, while lowincome individuals may lack the resourcesto escape high temperatures. And someminority groups carry an unequal shareo the heat burden (those both older and

less affluent than the general population),raising environmental justice concerns[18]. Additionally, individuals living insocial isolation are more vulnerable to heatbecause o the absence o a social networkto contact during heat waves [19].

With the continued aging o the USpopulation combined with projectedincreases in urbanization and extreme heat,heat-related illness and death will becomemore prevalent over time. Since the publichealth effects o urban heat are largelypreventable, health officials are developingheat response plans to prepare or the healthconsequences o rising temperatures. Asthese plans tend to be limited to actionstaken during the onset o a heat wave, thereis a urther need or municipal and regionalgovernments to develop heat management


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strategies that may lessen the intensity oheat both during heat waves and the warmseason in general. Tis report provides theoundation or such a heat managementplan in the Louisville Metro region.

1.2.1 Risks for Infrastructure and Private

Property: While the health risks associatedwith extreme heat are o great importance,risks to property and critical urbaninrastructure can also be significant.

Urban transportation inrastructureis increasingly stressed with rising

temperatures. Most transportationinrastructure is designed to last severaldecades, but with continued warming andan increase in the requency, intensity,and duration o heat waves over time,significant stress will be placed on thesesystems [20]. For example, extreme heatincreases the maintenance and repair costsor roads and railroad tracks. Prolongedexposure to high temperatures causes darkly

hued surace paving to sofen and expand,leaving potholes and ruts. Te warpingo both transit and reight railroad trackshas become increasingly common withheat waves o greater intensity over the lasttwo decades [21]. Both roadway pavingand railroad tracks can be engineered orhigher heat tolerance, but each materialhas a maximum temperature threshold andlittle inrastructure currently in place isdesigned or the extremity o heat alreadyexperienced in recent heat waves [22].

Air transportation is impacted by extreme

heat, as the lower density o hot airimpedes aircraf lifoff climb perormance,potentially requiring longer runway lengthsas regional climates warm. Te impact oextreme heat on a transportation systemis ar reaching because the interdependentnature o these systems. For example, heat-related flight delays or cancellations maylead to increased roadway or rail systemcongestion [23].

The elderly are more

vulnerable to heat

illness than any other

group.



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Extreme heat can cause electricity and waterdelivery systems to ail during periods opeak demand. Extreme heat causes metal

power lines to expand and impedes theefficiency with which transducers shedheat, lowering the overall efficiency othe system. Te increased demand andinefficiency o the power system mayoverwhelm the power generation capacityo a region, leading to unplanned blackoutsor intentional power outages by electricutility companies reerred to as rollingblackouts. From 1985-2012, the number omajor blackouts, i.e., those affecting more

than 50,000 homes or businesses, increasedtenold [24].

Similar to electrical demand, residentialand industrial water demand tends to risewith increasing temperatures. In US cities,temperatures above 70°F have been oundto elevate water use above normal levels,while temperatures in excess o 86°F lead

to significant increases in water demand[25]. As climate change and regionaldevelopment lengthen periods in excess

o these temperature thresholds, waterdelivery systems may be increasinglystressed, resulting in potential water mainbreaks and increasing the cost o managingthese systems. Mitigation o the urban heatisland effect provides a set o managementstrategies that can extend the lie andefficient perormance o critical urbaninrastructure.

1.3 UHI ManagementStrategies

Tree classes o heat managementstrategies have been demonstrated tolower air temperatures through small-scaleexperiments and larger scale modelingexercises. Tese strategies include theengineering o roofing and surace paving

Prolonged exposure

to extreme heat can

produce kinking in the

steel tracks of freight

and urban transit railsystems.


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materials to reflect away incoming solarradiation; enhancement o the surace areao trees, grass, and other plant material;and a reduction in waste heat emissionsbrought about through energy efficiencyprograms. wo additional sets o heatmanagement strategies, increasing thearea o surace water and wind ventilation

achieved through a redesigning o the builtenvironment, are not explored throughthis study due to concerns over near-termeasibility and the current prevalenceo water in proximity to the city. In thissection, we explore the potential benefitso “cool materials,” greenspace, and energyefficiency strategies.

1.3.1 Cool Materials: Cool materials are

paving and roofing materials engineeredor high surace reflectance, a thermalproperty technically known as “albedo.”Albedo can be thought o as the whitenesso a surace material, as lightly hued colorsare more reflective than darkly huedcolors. In reflecting away incoming solarradiation, high albedo materials absorb lessheat energy rom the Sun and atmosphere,lowering surace temperature. In additionto albedo, a second thermal property known

as “emissivity” can be engineered in coolmaterials to enhance the rate at whichabsorbed solar energy is re-emitted to theatmosphere. High emissivity materialstend to store less heat energy, which alsocontributes to a lower surace temperature.While the first generation o cool roofingand paving materials were white or off-white in color, a ull palate o colors, rangingrom white to dark grey, are commerciallyavailable today.

Cool materials can significantly lower thesurace temperatures o roofing shingleand surace paving. While the differencebetween surace and near-surace airtemperatures above conventional roofingcan be greater than 100°F, cool roofingproducts can reduce this differential by 50%or more [26]. Research has shown that

large-scale implementation o cool materialscan reduce air temperatures by more than3°F at the urban scale [27]. Most suitable orflat or low sloping roos, very high albedomaterials may create undesirable glareissues i applied to surace paving.

Like green roos, cool materials have

higher initial costs per square oot thanconventional materials, but these uprontcosts are more than offset over the materialliespan by savings realized throughreduced rates o weathering and, or roofingproducts, energy savings realized throughlower air conditioning costs [28]. Te CoolHomes Project in Philadelphia, or example,documented a 2.4°F reduction in indoor airtemperatures afer the installation o a cool

roo [29]. Although cool roofing materialsgenerally cost 0 to 10 cents per square ootmore than conventional roofing materials,the average yearly net savings o 50 centsper square oot makes this a cost-effectiveroofing option [30].

In US cities, surace paving is a significantand, in some cases, dominant land covertype, elevating the potential or cool pavingmaterials to reduce surace temperatures

throughout a metropolitan region. Whilecool paving materials are engineered or alower albedo than cool roofing materials, tominimize glare, paving materials exhibitinga moderate reflectivity can significantlyreduce urban temperatures due to theirexpansive surace area.

One property o cool paving that isdistinct rom cool roos as an urban heatmanagement strategy is porosity. Byengineering paving materials or both amoderately high albedo (cool paving) andhigh porosity (pervious paving), newlysuraced streets, parking lots, sidewalks, anddriveways can moderate air temperaturesthrough two mechanisms. First, the higheralbedo o cool paving reflects away a higherproportion o incoming solar radiation thanconventional asphalt. Second, the ability o


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solar energy to convert water to water vapor

thus limiting the quantity o solar energyavailable to increase surace temperatures.A single oak tree transpires up to 40,000gallons o water a year, while an acre o corntranspires up to 3,000 to 4,000 gallons owater a day [31], returning large quantitieso water to the atmosphere and lowering airtemperatures in the process (Figure 1.4).

In addition to evapotranspiration, treescool the suraces o the surrounding

environment through shading. reebranches and leaves block incoming solarradiation rom reaching land suracesbeneath the canopy. Generally, trees areeffective at blocking 70 to 90% o solarradiation in the summer and 20 to 90%in the winter [32]. Te position o atree impacts its effectiveness in coolingbuildings, as trees located on the west or

pervious pavement to allow the infiltration

o rainwater through the material enablesevaporation rom water stored in thepavement and rom the underlying soil,urther reducing temperatures. Manycities are investing in cool and perviouspaving as a strategy to manage both risingtemperatures and flooding events withclimate change.

1.3.2 Greening Strategies: rees, grass,and other vegetation in cities provide a

wide range o environmental and publichealth benefits, one o which is a coolingo the ambient air. Green plants can lowerair temperatures through the processes oevaporation (the transer o water to water vapor on plant suraces) and transpiration(the transer o water to water vaporin plant cells), reerred to in concert as“evapotranspiration,” which makes use o

A cool roof is an urban

heat management

strategy that pays foritself through reduced

energy costs for air

conditioning.


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southwest sides o a building block the mostsolar radiation rom reaching the building[33].

rees are added to the urban orest throughopen space planting to shade suraceslike grass and curbside planting to shadeimpervious suraces, such as streets and

parking lots. Studies have ound significantincreases in tree canopy to be associatedwith measurable reductions in ambienttemperatures. Trough climate modelingstudies ocused on New York, Philadelphia,and Baltimore, or example, a 40% increasein urban tree cover was ound to decreaseair temperatures by an average o 1.8to 3.6°F, with some areas experiencingtemperature reductions in excess o 10°F

[34].

Similar to tree canopy cover, thedisplacement o impervious materials bygrass has also been ound to lower urbantemperatures. Conversion o commercialroo areas to green roos is an increasinglycommon heat management strategy inlarge cities, with over 20% o all roofopsin Stuttgart, Germany, or example, now

planted with various species o grass,sedum plants, or even shrubs and trees[35]. Research shows that the suracetemperatures o green roos can be up to90°F cooler than conventional roos duringthe summer [36]. While the benefits ogreen roos or citywide air temperatures aredifficult to measure directly, one modeling

study finds the conversion o 50% o allroofops to green roos in Ontario, Canada,to produce a cooling effect o 3.6°F [37].While green roos are more expensive thantraditional roofing to install, long term costsavings in the orm o reduced buildingenergy consumption and increased roomembrane lie ully offset these costs overtime [38]. In this study, we model theeffects o a relatively small number o new

green roos in the urban core o Louisville.

A final greenspace heat managementstrategy examined in this study is theconversion o barren land to grass.Characterized by eroded soils and sparse vegetative cover, barren land can exhibitsimilar thermal properties to imperviouscovers, such as concrete. As such, extensiveareas o barren land in cities may elevate air

Figure 1.4Evapotranspiration

in green plants uses

solar energy to

convert water to water

vapor and cools the

air (NASA)


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cannot be created or destroyed.A direct outcome o this law is that anytimeenergy is utilized to power a vehicle, abuilding’s mechanical air conditioningsystem, or an industrial process, orexample, waste heat energy is released tothe environment. Te US Departmento Energy estimates that 20 to 50% o the

energy input or industrial processes, onaverage, is lost as waste heat [41], with vehicles typically losing 50% or more o theenergy in uel to waste [42]. In dense urbanenvironments, the quantity o waste heatenergy emitted can account or a significantproportion o a city’s urban heat islandeffect. As a result, reductions in vehicleuse, increases in vehicle uel efficiency,and increases in building energy efficiency

temperatures. When comparing the suraceradiant temperatures o several vegetatedand non-vegetated land cover types, urbanland and barren land have been ound toexhibit the highest temperatures [39]. In a10-year study o temperature trends acrossthe United States, barren land was ound tobe warming over time more rapidly than

any other land cover type, including urbanland covers [40]. In light o these findings,we measure in this study the effects oconverting barren land to grass throughoutthe Louisville Metro region.

1.3.3 Energy Efficiency and WasteHeat: According to the first law othermodynamics, energy can betransormed rom one orm to another but

Many streets in Louisville’s west sideneighborhoods lack sufficient street treecover, contributing to elevated tempera-tures.


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provide viable strategies or both reducingthe intensity o a city’s heat island and thequantity o greenhouse gas emissions.

Trough this assessment o heatmanagement strategies in Louisville, weestimate the benefits o policies designed to

lessen waste heat emissions rom vehiclesand buildings. While previous work hassought to assess how greenspace and coolmaterials strategies can be combined tolower air temperatures in US cities, thisassessment is the first to estimate thebenefits o combining these approacheswith energy efficiency strategies. Given thatmost US cities, including Louisville, havedeveloped climate action plans designed tolessen regional greenhouse gas emissions

through energy efficiency strategies, thisstudy provides a basis to account oradditional benefits o these programs in theorm o urban heat management.

Green roof installed

atop the American

Life building in

Downtown Louisville.


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blished and well maintained tree

opy in Old Louisville. Louisville Urban Heat Management Study 19


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2 HeatManagementScenarios

How effective would the implementation o

heat management strategies be in coolingLouisville? Prior to developing a heatmanagement plan or the Louisville Metroregion, it is important to assess the potentialbenefits o such strategies or both reducingsummertime temperatures throughout the cityand or preventing heat-related illnesses, suchas heat exhaustion and heat stroke, which aremost pronounced during periods o very hotweather.



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Trough the use o a regional climatemodel, this study estimates the impacto the three classes o heat managementstrategies discussed above – cool materialsstrategies, greening strategies, energyefficiency strategies – and all three othese strategies combined, to assess howregional temperatures might change were

these strategies to be implemented widelythroughout the Louisville Metro area. Wethen make use o a health impact modelto assess how any estimated changesin temperatures could reduce heat-related illness at the scale o individualneighborhoods. Te results o thismodeling study provide a basis or targetingheat management strategies to the areaso the region most vulnerable to health

impacts resulting rom extreme heat.

Why does this study make use o acomputer model to estimate the benefitso heat management across the LouisvilleMetro region? Regional climate models

provide an essential tool or estimatingtemperatures in all areas o a metropolitanregion. At present, only two NationalWeather Service stations are routinelycollecting temperature data in Louisville.As a result, it is not possible to accuratelygauge heat exposure within areas o theregion that lack a weather station. Te use

o a climate model enables air temperaturesto be estimated or every ½ by ½ kilometerarea (equivalent to about six city blocksin downtown Louisville) across the entiremetropolitan area – effectively increasingthe number o temperature measurementsrom two to almost 5,000. Figure 2.1presents the climate model grid developedor this study. Te use o a climatemodel enables heat exposure in every

neighborhood to be estimated.

A second benefit o regional climate modelsis that they enable the potential impacts oheat management strategies to be estimatedEven were there a large number o weather

Figure 2.1 Climate

model grid. The

Weather Research

and Forecasting

regional climate modelgenerates unique

temperature, humidity,

and windspeed

estimates for each of

4,924 grid cells across

the Louisville Metro

region. Note: The

CBD is the downtown

or Central Business

District.


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Our approach to assessing the potentialbenefits o heat management in Louisvilleconsists o our steps, including aninventory o land surace materials, themodeling o regional temperatures undercurrent conditions, the modeling o regionaltemperatures in response to each o theheat management strategies, and, lastly,

the estimation o health benefits associatedwith heat management planning acrossLouisville. In this section o the report,we describe each o these steps in the heatmanagement study.

2.1 Inventory of Land Surface

Materials

Te regional climate model used inthis study – the Weather Research andForecasting Model (WRF) – is driven bythree basic sets o climatic inputs. Teseinclude: 1) the weather conditions movinginto the modeling area at the start o themodeling period; 2) the weather conditionso the modeling area itsel at the start o themodeling period; and 3) the land suracecharacteristics o the modeling area, whichare held constant during any single scenario

run. Based on these provided conditions,the WRF climate model estimates aseries o weather variables, including airtemperature, humidity, and wind speed,or every approximate ½ kilometer by ½kilometer (reerred to as ½ km2) grid cellacross Louisville. Tese weather variablesare estimated or every 1-hour interval overthe period o May 1 through September30 in the year 2012. We selected the 2012warm season as the modeling period or

this study as this was an unusually warmsummer. Each o the heat managementscenarios modeled in this study arebased on regional weather, land use, andpopulation characteristics consistent with2012.

Development conditions around theLouisville Metro area have a significantinfluence on air temperatures. As described

stations distributed across the LouisvilleMetro area, such a network would onlycapture how temperatures vary acrossthe region under current developmentconditions. o better understand howtemperatures might change in response tothe implementation o heat managementstrategies, a regional climate model was run

or current day conditions and then runagain to assess how an increase in the useo cool construction materials, an increasein vegetation, and an increase in buildingand vehicle energy efficiency might changetemperatures at the neighborhood level.Only a climate model enables such anassessment.

Do regional climate models estimate

temperature with a high degree oaccuracy? As our understanding o regionalclimatology has improved, along withcontinuing improvements in computerprocessing capacity, the accuracy withwhich regional climate models can simulatecurrent day temperatures has increasedsubstantially. I such models are to be usedto inorm public policy and investment, itis essential that these tools be demonstratedto model climate with a high degree o

precision. o do so in this study, we runthe regional climate model or a recent timeperiod or which continuous temperatureobservations are available rom regionalweather stations. We then compare howaccurately the computer model estimatesair temperatures in the limited number oareas where observations are available. Teresults o this comparison show the climatemodel to simulate average temperaturesover the period o May 1 to September 30,2012 (reerred to in this report as the “warmseason”), at Louisville’s two airport locationswithin 0.3o F o observations, representinga very close level o agreement betweenobserved and modeled temperatures.Based on this outcome, we assume theresults o our scenario modeling to providea sufficiently high degree o reliability toinorm regional policy development.


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land use, we make use o satellite-measuredland use inormation obtained rom the USGeological Survey (USGS). Classes o landcover obtained rom the USGS databaseinclude tree canopy, grass, shrubs, croplandpastureland, barren land, water, andwetland areas. Te availability o data onboth impervious and non-impervious land

use conditions across the Louisville Metroarea enables the estimation o the percentcoverage o each o 15 classes o land cover(able 2.1) within each grid cell, whichmay then be used to drive the WRF climatemodel.

Te scenario climate modeling undertakenor this study is driven either by changesin current (2012) land cover conditions or

by changes in total energy consumption –producing changes in waste heat emissions– or each grid cell across the modelingarea. Each o our heat managementscenarios entails either the conversion oimpervious areas (paving or roofing) to coomaterials or vegetation, or a reduction inthe total quantity o waste heat generatedby buildings and vehicles. Te resultingland cover or energy efficiency changesassociated with each heat management

scenario are presented in Section 3.

above, the presence o expansive areas osurace paving in the orm o roads andparking lots, in combination with buildingareas, tends to absorb large quantities osolar energy and to re-emit this energy asheat, raising air temperatures. Tus, zoneso the county that are intensely developed,such as the central business district, will

generate their own hotspots, in whichair temperatures are measurably higherthan in undeveloped or residential zoneswith ample amounts o tree canopy, lawnarea, and other vegetation. Te accuratemodeling o air temperatures across themetro area thus requires inormation on theland surace materials ound in each modelgrid cell.

wo sources o inormation are used to mapland surace materials across Louisville.First, we make use o parcel and roadwayinormation provided by the Louisville /Jefferson County Inormation Consortium(LOJIC). LOJIC maintains very detailedand high quality geographic inormationon all impervious suraces throughoutthe county, including roadway areas bytype (neighborhood streets vs. highways),building areas by type (residential buildings

vs. commercial buildings), and other typeso surace paving, including parking lots,sidewalks, and driveway areas. o classiythe non-impervious components o county

Table 2.1 Land cover

classes used as inputs

to WRF climate model


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this section, we present the policy-basedassumptions driving each o the five heatmanagement scenarios.

2.2.1 Current Conditions: Te CurrentConditions scenario models temperature

and humidity in response to currentday development patterns. As such, themix o surace paving, roofing materials,tree canopy, grass, and other land covercharacteristics ound in each grid cellmatch as closely as possible the currentday development patterns. Te CurrentConditions scenario is first used to validatethe climate model based on temperature

2.2 Heat Management

Scenarios

emperature and humidity were modeledacross the Louisville Metro region inresponse to five land developmentscenarios, including Current Conditions,Cool Materials, Greening, Energy Efficiency,and all strategies combined (CombinedStrategies) scenarios. Tis mix o modelingscenarios was selected to assess thepotential benefits o each heat managementtechnique as a stand-alone strategy and inconcert with other heat mitigation tools. In

emporary parking lots in the SouthLouisville neighborhood are a com-mon example o barren land in largecities like Louisville.


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higher values associated with a more rapidrelease o absorbed solar energy.

Trough the Cool Materials scenario,different values o albedo and emissivityare applied to different types o suracematerials. Because highly reflectivematerials, such as a bright white paving,

can create glare problems or drivers andpedestrians, more moderate levels o albedoare applied to streets, parking lots, and othertypes o surace paving. As non-residential(i.e., commercial and industrial) buildingroofops are ofen characterized by lowsloping or flat roos, high levels o albedoare applied to these suraces, as the potentialor street-level glare rom these roos islow. Lower levels o albedo and emissivity

are applied to the typically pitched roos oresidential structures.

2.2.3 Greening Scenario: Trough theGreening scenario, the area o tree canopyand grass is increased across Louisville tomoderate temperatures through increasedshading and evapotranspiration. Teaddition o new tree canopy and grass istargeted toward areas o high developmentdensity, where vegetation tends to be most

sparse. o direct where new tree canopyand grass areas should be targeted, thestudy assumes two new land use policiesto be in place in the region. Te first isa new zoning tool reerred to as a “greenarea ratio.” Recently adopted in several UScities, including Seattle, Washington, andWashington, DC, a green area ratio policysets minimum green cover targets or allresidential, commercial, and industrialparcels that may be met through a widerange o landscaping techniques, includingtree planting, traditional lawn areas, raingardens, and green roos, among otheroptions. Figure 2.2 presents landscapingtechniques permissible under the Seattle“Green Factor” ordinance.

Once in place, all new development andexisting properties undergoing renovation

observations rom regional weather stations.As discussed in the preceding section,model estimates o temperature generatedin response to current development patternsmatch very closely regional measurementsduring the summer o 2012. Te CurrentConditions scenario is also used in thisstudy as a baseline set o temperature and

humidity estimates against which the heatmanagement scenarios are measured. Itis expected that increased levels o coolmaterials, vegetative cover, and reductionsin waste heat emissions, as modeled throughthe various heat management scenarios,will be ound to lower temperature andhumidity levels, on average, across theLouisville Metro study area.

2.2.2 Cool Materials Scenario: Roads,parking lots, and building roos accountor a large percentage o the total suracearea in downtown Louisville. On average,grid cells in the city’s central businessdistrict neighborhood are more than 65%impervious, with the remainder typicallyoccupied by grass, trees, barren land, andwater. Trough the Cool Materials scenario,the reflectivity or “albedo” o roofing andsurace paving is increased to reduce the

quantity o sunlight absorbed by thesematerials and re-emitted as sensible heat.Surace albedos are measured on a scale o0 to 1.0, with values o 1.0 approaching thereflectivity o a mirror. Dark materials withhigh surace roughness, such as new blackasphalt roofing shingle, exhibit albedos aslow as 0.05.

A second thermal property o imperviousmaterials – the emissivity, or efficiencywith which absorbed solar energy is re-emitted as sensible heat – is also increasedthrough this scenario to reduce materialtemperatures. High emissivity materialsquickly release absorbed solar energy,reducing the quantity o solar energy thatis retained by these materials and thuslowering temperatures. Termal emissivityis also measured on a scale o 0 to 1.0, with


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vacant parcels. As barren land is mostlydenuded o vegetation, its exposed soil

can contribute to elevated solar absorptionand sensible heating much in the sameway a roadway or parking lot elevates localtemperatures. o limit the thermal impactso barren land, we assume 80% o the barrenland ound in any grid cell is converted tograss through the implementation o anurban barren land management policy.

Te Greening scenario model simulationis carried out by adding vegetation to eachgrid cell until the minimum green covertargets are met or exceeded. Te first step inthis simulation increases street tree coverageto meet minimum targets set by street type,as reported in able 2.3. Next, 80% o thearea o barren land ound in any grid cellis converted to grass, as outlined above.Following these two steps, 70% o the 4,924grid cells in the Louisville Metro study area

are brought into compliance with theminimum green cover standards. o tailor

a set o minimum green cover standards,we first estimated the average green coverby zoning class across Louisville and thenadopted green area targets that would havethe effect o increasing green cover in themost densely developed zones. able 2.2presents the minimum green cover targetsby zoning class. Based on these targets, treecanopy and grass area is added to any gridcell in which the minimum green coverstandard, based on the mix and area ozoning classes ound within the grid cell, isnot met.

A second new land use policy assumed tobe in place in the Louisville Metro regionis a limitation on the area o barren landper parcel. Examples o barren land includeconstruction sites, poorly maintainedresidential lawn areas, and non-vegetated

Figure 2.2 Greening

techniques

permissible under

Seattle’s Green

Factor ordinance


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well, lowering the release o heat energy tothe ambient air through vehicle tailpipesand air conditioning compressors. Asnoted above, waste heat emissions rom vehicles and buildings have been ound toaccount or a third or more o the urbanheat island effect in some US cities [43].Trough the Energy Efficiency scenario

the average quantity o waste heat emittedrom roadways and buildings is reduced bya fixed percentage responsive to ongoingand anticipated improvements in energyefficiency. In response to ederal and statepolicies, vehicle uel and building energyconsumption in Kentucky have allen overa recent five-year period by 5 and 4%,respectively. I these trends continue overthe next ew decades, a period in whichenergy improvements are projected to

accelerate, vehicle uel and building energyconsumption in Kentucky may all by 25and 20%, respectively [44].

For the Energy Efficiency climate modelscenario, we assume reductions in vehicleuel consumption o 35% and buildingenergy consumption o 30%, reflectingonly a modest increase over projected

were ound to meet or exceed the minimumgreen area ratio standards presented inable 2.2.

For the remaining 30% o grid cells ailingto meet the green area minimum, 50% o allsurace parking lot areas are converted totree canopy, which increases the percentage

o study area grid cells meeting or exceedingthe assigned green area minimum to about95%. As a final greening strategy, 25% othe roo area o all non-residential buildingsis converted to green roos in the smallnumber o grid cells still ailing to meet thedesignated green area minimum. With thecompletion o this step, more than 99% ostudy area grid cells meet the designatedgreen area minimum. No additionalgreen area is added to the small number

o grid cells ailing to meet the green areaminimum.

2.2.4 Energy Efficiency Scenario: As cars,trucks, and building heating and coolingsystems consume less energy over time withtechnological improvements, the quantityo waste heat emitted per mile driven orper unit o indoor climate control alls as

Table 2.3 Target

street tree cover

minimums by road

type

Table 2.2 Minimum

green cover targets

used for Greening

scenario


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trends or Kentucky over the next ewdecades. Te resulting reduction in wasteheat released in the Louisville Metro area isexpected to achieve a modest cooling effect,independent o changes in vegetation andsurace reflectivity.

2.2.5 Combined Strategies Scenario:

Te fifh and final heat managementscenario carried out or this study entailsthe combination o the Cool Materials,Greening, and Energy Efficiency scenarios.While each heat management strategy isexpected to yield temperature reductions,on average, when applied as a stand-alonestrategy, prior work suggests that thecombination o strategies will achieve themost significant reductions in regional

temperatures. Trough the CombinedStrategies scenario, all greening strategieswith the exception o green roos are appliedfirst, ollowed by the application o coolmaterials assumptions or all remainingimpervious suraces. Cool roos are usedin place o green roos in the CombinedStrategies scenario due to the greater costo green roo installation. Te resultingsurace materials changes, including newtree canopy, new grass, and higher levels

o albedo and emissivity or all imperviousmaterials by type, are then input into theclimate model in concert with the wasteheat emissions assumptions resulting romthe Energy Efficiency scenario. able 2.4reports the total area o modified suracematerials, including both new vegetationand cool materials, or the CombinedStrategies scenario.

2.3 Health ImpactAssessment

Frequent and prolonged exposure tohigh temperatures produces adversehealth effects directly tied to climate andexpected to worsen with climate change.o evaluate the health protection benefitso urban heat management strategies,

we assess the population sensitivity to varying temperatures under each heatmanagement scenario. An establishedrelationship between temperature andmortality is used to evaluate the numbero lives saved in Louisville ollowing urbanheat management actions, compared withcurrent summer conditions.

Several basic elements o data are combinedto perorm our health impact modeling.First, population estimates were obtainedrom the US Census and allocated toeach ½ km2 grid cell in the region. Censusinormation used in the health modelingincludes number o people by age, sex,ethnicity, and race.

Second, we obtained data on average dailymortality rom the US Centers or DiseaseControl and Prevention (CDC). Tis datawas acquired or the Louisville Metro arearom the CDC’s Wide-ranging ONlineDatabase or Epidemiologic Research(CDC-WONDER) and allocated to eachgrid cell in the metro region.

Tird, an exposure-response relationshipbetween temperature and mortality was

obtained rom a recent study on extremeheat and heat-related mortality publishedin Te Lancet [45]. Te study providesdata on the measured association betweentemperature and heat-related mortalityor more than 384 cities around the world,including Louisville. Using this inormationthe risk o heat mortality can be estimatedor each day in the 2012 warm season (Maythrough September) across each grid cell inthe Louisville Metro region.

Finally, the grid cell daily temperaturesrom the climate scenario modeling areused to estimate the number o heat-relateddeaths in response to current conditionsand each heat management scenario. As theheat management scenarios modiy dailytemperatures in different areas o Louisvillethe estimated number o heat-related


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deaths will change as well. Importantly, thenumber o heat-related deaths in any area othe region will be a product not only o thecorresponding neighborhood temperaturebut also o the population compositiono the neighborhood. Neighborhoodsconsisting o larger populations, or oa disproportionate number o sensitiveindividuals (such as the elderly), will beound to have a higher number o heat-related deaths than neighborhoods withlower populations, assuming the samedegree o temperature change in both areas.Te results o the heat-related mortalityassessment are reported in Section 4.

Table 2.4 Total

modied area for the

Cool Materials and

Greening scenarios


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3 HeatScenarioResults

How might the implementation o heat

management strategies moderate temperaturesacross the Louisville Metro region? In thisthird section o the report, we present theresults o the heat management scenariomodeling to assess how an enhancement incool materials and regional vegetation, inconcert with reduced waste heat emissionsrom building and vehicles, might reduce the

urban heat island effect in Louisville.



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districts, tree canopy cover is less than15%. Te most heavily orested zones othe county are ound in the northeastern,eastern, southwestern areas and alongthe Ohio River. In contrast to most otherland cover types, tree canopy is ound torange rom a low level o zero coverageto 100% coverage in heavily orested

areas o the county. ree canopy areas vary widely by residential neighborhood,with neighborhoods to the east and southtypically exhibiting higher coverages thanthose o the inner urban core and to thewest o downtown. As discussed in Section2.2.3, the Greening scenario is designed tostrategically enhance tree canopy cover inthe most sparsely canopied residential andcommercial zones through the planting

o trees along streets and within suraceparking lots.

3.1.2 Grass Cover: Similar to tree canopycover, areas o grass were mapped throughthe use o satellite imagery and aerialphotography. Te distribution o grass coverthroughout the Louisville Metro studyarea tends to be ound outside o heavilyorested zones (Figure 3.2). In contrast tothe heavily orested areas to the ar south

and eastern zones o the county, grass landcovers are most dense in the western andcentral zones, with even some o the heavilypopulated areas o the inner city core oundto have coverages in excess o 35%. Grasscovers range rom zero to 80%, are heaviestin residential zones, and are most sparsein commercial and industrial zones. Grasscover is enhanced through the Greeningscenario by decreasing the area o barrenland and through modest increments in thearea o green roofing.

3.1.3 Barren Land: A third class o non-developed land that is modified throughthe climate scenario modeling is barrenland. Consisting o active constructionsites, poorly maintained lawn areas, andzones subject to extensive erosion orother vegetation-denuding conditions, the

3.1 Land Surface Materials

Inventory

Trough the land surace materialsinventory, 15 distinct classes o landcover were estimated at the grid celllevel throughout the Louisville Metro

area. wo o the vegetative land coverclasses – tree canopy and grass – and ouro the impervious land cover classes –residential roo area, non-residential rooarea, roadway paving, and non-roadwaypaving – were changed through the climatesimulations to assess how increased areas o vegetative cover and cool materials wouldmodiy temperatures around the LouisvilleMetro area. In this section o the report,we present a series o maps detailing the

present day (2012) distribution o these landcover materials throughout the study areaand then illustrate how these land coverdistributions were modified through eachheat management scenario.

3.1.1 Forest Cover: Tree classes o treecanopy cover were estimated throughoutthe Louisville Metro study area, includingthe area o deciduous trees, conieroustrees, and areas o mixed deciduous andconierous trees. For large contiguous tractso orestland, satellite imagery was usedto map the spatial extent o tree cover. Inmore densely developed areas o the county,satellite imagery was combined with air-photo interpretation to quantiy areas ostreet trees, yard trees, and smaller patcheso tree canopy in public spaces. Figure 3.1presents the percent o total orest cover,including both deciduous and conierous

tree species, or each grid cell throughoutLouisville.

Te distribution o tree canopy presented inFigure 3.1 is consistent with the findings othe recent Urban ree Canopy Assessment,which ound the area o tree cover in themost intensely developed regions o thecounty to be very sparse. For most gridcells in the downtown and airport/industrial


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Figure 3.1 Tree

canopy cover across

Louisville Metro

region as percentage

of ½ km2 grid cell

Figure 3.2 Grass

cover across

Louisville Metro


of ½ km2 grid cell


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exposed soils o barren land can elevatelocal temperatures in a manner similarto impervious materials. As described inSection 2.2.3, one o the initial steps in theGreening scenario entails the conversion o80% o any barren land within a grid cell tograss. Figure 3.3 presents the distributiono barren land throughout Louisville under

current conditions. While ew grid cellshave extensive areas o exposed soil – ashigh as 70% o the grid cell area in somecases – barren land tends to account or lessthan 10% o all land covers throughout thestudy area. Similar to grass land covers, thedistribution o barren land tends to ollowthe pattern o single-amily residentialdevelopment, suggesting that exposed soilsare ofen associated with poorly maintained

lawn areas.

3.1.4 Surface Impervious Cover: Severalclasses o impervious land cover are mappedor the current conditions scenario and thenmodified in the scenario modeling throughincreased street tree planting, parking lottree planting, and green roos. Suraceimpervious cover consists o the imperviousareas o roadways – ranging rom localneighborhood streets to interstate highways

– parking lots, walkways, and driveways.Figure 3.4 presents the distribution oroadway impervious cover throughoutLouisville and clearly reveals the patterno interstate highways and other largeroadways around the county. Also asexpected, the downtown district and nearwestside neighborhoods are ound to havehigh levels o imperviousness.

Presented in Figure 3.5, the pattern oimperviousness associated with parkinglots, sidewalks, driveways, and airportrunways is more consistently clusteredaround commercial and industrial districtsthan is roadway paving. In addition tothe downtown and westside districts,the Louisville International Airport andother industrial zones are ound to becharacterized by extensive surace parking

and non-roadway imperviousness.

3.1.5 Building Impervious Cover: Building impervious covers consist o theroofing area o all buildings, includingboth residential and non-residentialstructures. Figure 3.6 maps the distributiono residential building areas under current

conditions. Te map reveals a set o well-defined, finger-like patterns o residentialdevelopment radiating rom the downtowndistrict, which is not characterized byhigh levels o residential development.Te green axis o Cherokee and Senecaparks, flowing into Bowman Field, providecleavage between the residential areas othe Highlands and Crescent Hill and St.Matthews to the east, while the industrial

zone around the Louisville InternationalAirport clearly partitions the Audubon Parkarea rom Shively.

Commercial and industrial building areadistributed around Louisville is a less welldefined pattern (Figure 3.7), but with theexpected concentrations o development inthe downtown district, airport/industrialzone, and around the commercial districto Jeffersontown. Due to the prevalence o

flat or low sloping roos in commercial/industrial zones, these areas are prioritizedor highly reflective cool roos and/orgreen roos through the Cool Materials andGreening scenarios.

3.2 Surface Temperature

Analysis

Prior to perorming the climate model

simulations, surace temperature acrossthe Louisville Metro area was mappedthrough the analysis o a thermal satelliteimage. Te Landsat EM satellite capturessurace temperature over the Louisvilleregion every 16 days at a spatial resolutiono 30 meters (i.e., temperature is measuredor every 30 meter by 30 meter area acrossthe region). Trough the processing o


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Figure 3.4 Roadway

paving area across

Louisville Metro


of ½ km2 grid cell

Figure 3.3 Barren

land across

Louisville Metro


of ½ km2 grid cell


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Figure 3.6

Residential building

roof area across

Louisville Metro


of ½ km2 grid cell

Figure 3.5 Non-

roadway surface

paving area across

Louisville Metro


of ½ km2 grid cell


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estimate the distribution o summer airtemperatures throughout the LouisvilleMetro Region and to simulate howtemperatures might change in response tothe implementation o heat managementstrategies. In this section o the report,we present the results o these climatemodel runs and assess the relative benefits

associated with heat management strategiesimplemented alone and in concert. We firstpresent a set o three maps illustrating thedistribution o summer air temperaturesacross the Louisville Metro region undercurrent conditions (2012), in which no heatmanagement policies are assumed to bein place. In the remainder o this section,we present a series o two-panel mapsillustrating how each heat management

strategy influences maximum andminimum temperatures in the study areaand the spatial extent o cooling or warmingoutcomes resulting rom the simulatedchanges. Complete results reporting thechange in temperature by neighborhood arepresented in ables A.1-A.3 o Appendix A.

3.3.1 Current Conditions: Figure 3.9illustrates the distribution o daily high airtemperatures averaged over the period o

May though September (2012) across theLouisville Metro region. Both high and lowtemperatures are averaged over the entirewarm season to account or the variableeffects o heat on human health during thecourse o the spring and summer. In thelate spring, when the first hot temperatureso the year may be experienced andresidents may not yet be ully acclimatedto warm weather, vulnerability to heatillness may be elevated due to enhancedsensitivity. Later in the summer, when thepopulation is better acclimated to heat, butextreme temperatures can persist or manydays, vulnerability may be elevated due tothe duration and intensity o heat. For thisreason, the heat effects model used in thisstudy accounts or temperatures throughoutthe ull warm season to capture potentialhealth impacts o early, middle, and late

thermal data captured on July 5th, 2010– a day in which regional cloud coverwas minimal – surace temperature wasestimated and aggregated to the ½ km2 griddeveloped or this study. While suracetemperature does not provide a reliableindicator o human health impacts, itprovides a readily available data source or

identiying zones where the emission osurace sensible heat energy is unusuallyhigh, typically due to sparse vegetativecover and extensive impervious materials.An additional application o suracetemperature measurements is in identiyingthose areas subject to the greatest materialheat stress. As temperatures continueto rise in Louisville, streets, bridges, raillines, and other inrastructure may require

replacement in zones continually subject toextreme temperatures.

Figure 3.8 presents surace temperaturethroughout the study area as measuredrom the Landsat EM satellite. Te suracetemperature map finds a central north tosouth axis o high surace temperatureto run rom the downtown district to theairport/industrial zone about six miles tothe south. By contrast, heavily vegetated

zones, such as Cherokee and Seneca Parks,as well as heavily canopied neighborhoodsto the northeast o downtown, are oundto exhibit surace temperatures as muchas 40 degrees cooler. As to be expected,surace temperatures o the Ohio River aremuch cooler than that o any land eatures.In general, the surace temperature mapreveals a pattern o high temperatures thatis consistent with the pattern o imperviousland covers depicted in Figures 3.4 through3.7.

3.3 Air Temperature Scenario

Modeling

As outlined above in Section 2.2., theWeather Research and Forecasting regionalclimate model was used in this study to


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Figure 3.8

Distribution of

surface temperatures

throughout Louisville

Metro region

Figure 3.7 Non-

residential building

roof area across

Louisville Metro


of ½ km2 grid cell


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Likewise, on many days throughout thesummer o 2012, daily high temperaturesexceeded 100°F. Areas ound to averagedaily high temperatures in excess o 88°Fover the period o May through Septemberexperienced a very hot summer.

Figure 3.10 presents warm season

average daily low temperatures across theLouisville Metro region in 2012. ypicallyexperienced in the early morning hours– between 3:00 and 6:00am – the dailylow or minimum temperature has beenound to be more closely associated withthe occurrence o heat-related illness thanthe daily maximum temperature. Highnighttime temperatures stress humanrespiratory and cardiovascular systems by

prohibiting the body rom ully recoveringrom high heat exposures during theday. Elevated nighttime temperatures,particularly during heat wave periods andor individuals lacking access to mechanicalair conditioning, provide an importantindicator o which areas o the LouisvilleMetro region are most at risk to heat-relatedillness.

In contrast to the daily high temperature

map, Figure 3.10 reveals a smoother or lessheterogeneous distribution o temperaturesand five distinct hot spots. While the dailyhigh temperature or one zone can occurat a different time than another, due todifferential shading or cloud cover, daily lowtemperatures are more likely to be recordedduring the same hour, and thus the spatialdistribution o temperatures is moreuniorm. Average low temperatures areound to range rom 59 to 72°F, depictingan unusually intense average nighttimeheat island o 13°F. Also in contrast to thedaily high temperature map, Ohio Rivertemperatures tend to all into the highesttemperature category. Because watertemperatures change much more slowlythan land surace temperatures, the watertemperatures tend to be relatively coolduring the daytime hours and relatively

summer heat exposure.

Te daily high temperature map presentsa classic urban heat island temperaturepattern, with the highest temperaturesound in the most intensely developed zonesound in the downtown district and with agradual reduction in temperatures observed

across less intensely developed and moreheavily vegetated areas moving away romthe downtown core. As consistent with thespatial pattern o warming, Louisville’s mostdensely developed areas tend to be oundin the downtown district, immediately tothe west, in relatively dense and poorly vegetated residential areas, and then to thesouth and west across heavily industrialzones situated along the Ohio River. Te

lowest late afernoon temperatures tend tobe ound in the agricultural zones to theeast and within grid cells located in theOhio River.

Te temperature maps presented in thissection partition temperatures into fiveranges, each with an approximately equalnumber o grid cells. Tus, the zone ohighest average daily high temperatures(88 to 90°F) illustrated in Figure 3.9 is

approximately equal in total area to the zoneo lowest average daily high temperatures(85.0 to 86.5°F). Te distribution odaily high temperatures during the warmseason reveals an average maximum urbanisland intensity o about 5°F, which isconsistent with a large number o studiesacross numerous cities reporting a rangeo seasonal heat island intensities betweenabout 2 and 6°F. It should be noted that thetemperatures mapped in Figure 3.9 presentan average o 153 daily high temperaturesover the period o May through September,and thus the high temperature (or the heatisland intensity) on any particular daycould be much lower or higher than thosepresented here. On many days during the2012 summer, or example, the differencebetween the hottest and coolest areas oLouisville was ound to be in excess o 12°F.


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Figure 3.10 Warm

season (May

through September)

average daily low

temperature (°F)

in Louisville Metro

region

Figure 3.9 Warm

season (May

through September)

average daily high

temperature (°F)

in Louisville Metro

region. The Central

Business District

(CBD), Louisville

International Airport(Airport), and

regional interstate

highways are

labeled.


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scenario throughout virtually all o theLouisville Metro region (Figure 3.12).Te magnitude o reductions in daily lowtemperatures, however, is not as great asthe reductions in daily high temperatures.Due to the act that cool material coatingsare engineered to reflect away incomingsunlight, and thus cool land suraces

through a reduction in the quantity osolar energy absorbed, this approach is lesseffective in reducing temperatures duringthe nighttime hours, although coolingbenefits achieved during the day carry overinto the evening. Panel B o Figure 3.12finds reductions in warm season nighttimetemperatures o 0.5 to 1°F in the downtowndistrict and across and extensive area owest side neighborhoods, with reductions

in low temperatures or single hot nights tobe 3°F in some areas. Te Cool Materialsscenario is also ound to be associatedwith a small magnitude o warming in thesoutheastern region o the Louisville Metroarea, where population densities are low.Tis outcome is likely attributable to thedeflecting o heat energy away rom themost densely developed areas o the region.

3.3.3 Greening Scenario: Trough the

Greening scenario, new tree canopy isadded along roadways and within parkinglots, in concert with the conversion obarren land and a limited number ocommercial roofops to grass. In total,approximately 450,000 overstory trees wereadded through the Greening climate modelsimulation, equivalent to about 30 squarekilometers in total. A total o 31 squarekilometers o new grass cover was addedthroughout the Louisville Metro region,with 98% o this new grass resulting rombarren land conversions, and the remainderrom the creation o new green roos (seeable 2.4).

As illustrated in Figure 3.13, the Greeningscenario was ound to have a less extensivecooling effect on regional temperatures thanthe Cool Materials scenario. While Panel

warm during the nighttime hours.

Te highest nighttime temperatures areound across a similar downtown-to-westside hotspot revealed in Figure 3.10, as wellas within additional distinct hotspots nearShively and arther south. While hotpotzones tend to be characterized by extensive

impervious cover, other actors, such astopography, may play a role in the elevationo daily low temperatures. Te dailylow temperature map reveals numerousresidential zones characterized by elevatednight temperatures and associated heat risk,with the coolest areas alling into sparselypopulated agricultural zones to the east.

3.3.2 Cool Materials Scenario: Conversion

o building roo and street paving materialsto highly reflective “cool” materials isound to have a significant impact ontemperatures across the Louisville Metroregion. As presented in Figure 3.11 (PanelA), average daily high temperaturesthroughout the study area, particularlyin the downtown district and across westside neighborhoods, are significantly lowerin these areas than under the CurrentConditions scenario. Panel B o Figure 3.11

quantifies the change in average daily hightemperature or each grid cell in the studyarea under the Cool Materials scenariorelative to Current Conditions. Tis mapshows that virtually every grid cell in theMetro region experiences a reduction indaily high temperatures in response tothe coating o roadways and roofops withsunlight-reflecting materials. Areas allinginto the darkest blue zones experienced acooling effect o at least 1°F and, in manycases, in excess o 3°F. Presented here as awarm season average, the reduction in hightemperatures on single hot days was oundto be as high as 6°F.

Similar to high temperatures, averagedaily low temperatures during the periodo May through September o 2012 wouldhave been lower under the Cool Materials


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Figure 3.11 Warm

season (May

through September)

average daily high

temperature under

the Cool Materials

scenario (Panel A)

and temperature

difference relative to

Current Conditions

(Panel B)


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Figure 3.12 Warm

season (May

through September)

average daily low

temperature under

the Cool Materials

scenario (Panel A)

and temperature


Current Conditions

(Panel B)


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greatest. Relative to the Current Conditionsscenario, Panel A finds a significantreduction in the hotspots downtown andin the central area o the region, whilePanel B reveals a cooling effect acrossmost o the Metro area. With continuedevapotranspiration into the evening hoursand diminished effects o low reflectivity,

green plants play a key role in loweringnighttime temperatures in the urban core.

Te results presented in Figures 3.11through 3.14 raise an important questionor heat management planning in Louisville:Are cool materials more effective inlowering regional temperatures than greencover? On average the Cool Materialsscenario is indeed more effective in

lowering both high and low temperaturesregion-wide than is the Greening strategy.Te principal reason or this outcome,however, is simply due to the much greaterland area impacted by the cool materialsconversions than the addition o new treeand grass cover, as driven by the study’sassumptions. Overall, the total areaconverted to cool materials is almost threetimes as great as the total area convertedto new tree canopy and grass cover: 168

square kilometers o new cool suraces vs.61 square kilometers o new green cover.Tis outcome results rom the assumptionthat all roadway and roofing areas can beconverted to cool materials at the timeo routine resuracing at only modestadditional expense. Converting all roofingand paving areas to green cover, by contrast,would be both ineasible and prohibitivelyexpensive, and so only about 15% o theregion’s impervious cover is overlaid withnew tree canopy or grass.

Are cool materials more effective inlowering temperatures than green coverwhen comparing equivalent conversionareas? Our results find each new squaremeter o tree or grass cover to be 1.2 timesas effective as each new square meter o coolmaterials added in lowering average daily

B o Figure 3.13 shows significant coolingin a limited number o grid cells – withtemperature reductions between 1 andgreater than 2 °F – increased tree plantingand grass cover was generally ound to leadto a slight reduction or a slight increase inhigh temperatures across Louisville. Telikely reasons or these mixed effects are

twoold.

First, because green plants tend to have alow albedo or reflectivity, due to the darkhue o lea and grass area, an increase ingreen cover can lead to an increase in solarabsorption during daylight hours. Greenplants are very effective in offsetting areduced albedo through the process oevapotranspiration, through which the

release o water vapor cools lea suracesand the surrounding air, but this processmay slow during the hottest period o theday, as green plants work to conserve water.As a result, green strategies are ofen oundto be less effective in reducing maximumdaily temperatures than cool materials.

A second reason the Greening scenario wasound to have mixed results in loweringhigh temperatures during the warm

season relates to the seasonality o benefitsassociated with green strategies. In thespring, when tree canopy leas out anew,a resulting decrease in surace reflectivitymay produce more o a warming thana cooling effect. By the hottest monthso the summer, however, increasedevapotranspiration rom green plants tendsto ully offset a lower albedo, producinga net cooling effect. When averagingthe impacts o green strategies on hightemperatures or the ull warm season, thegreater benefits during the hottest monthsare diminished.

Figure 3.14, presenting the results o theGreening scenario or warm season lowtemperatures, finds a clear benefit orincreased tree and grass cover on lowernighttime temperatures, when heat risk is


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Figure 3.13 Warm

season average daily

high temperature

under the Greening

scenario (Panel A)

and temperature


Current Conditions

(Panel B)


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Figure 3.14 Warm

season (May

through September)

average daily low

temperature under

the Greening

scenario (Panel A)

and temperature


Current Conditions

(Panel B)


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3.3.5 Combined Strategies Scenario: Tefinal scenario simulated or the 2012 warmseason entailed a combination o the CoolMaterials, Greening, and Energy Efficiencyscenarios. As each o these classes ostrategies can be largely implementedindependent o one another, the combinedeffects o each land cover and waste

heat emissions strategy can be modeledsimultaneously. In doing so, tree plantingand grass conversion strategies are assumedto be implemented first, with all remainingunshaded roadway and unvegetated roofopareas then converted to cool materials. Teresults o this final model simulation arepresented in Figures 3.17 and 3.18.

As expected, the Combined Strategies

scenario was ound to have a moresignificant effect on metro areatemperatures than any stand-alone heatmanagement strategy. Figure 3.17 finds allregional high temperature hotspots to beoffset entirely (Panel A), with some areasin the urban core experiencing a warmseason average high temperature reductiono 3°F or more. Panel B shows expansivezones across the urban core, westsideresidential and industrial zones, and near

eastside zones to experience a reduction indaily high temperatures o at least 1°F, withtemperature reductions observed on singledays o more than 5°F in some areas. Onlya handul o grid cells exhibit a warmingeffect rom the Combined Strategiesscenario.

Under the Combined Strategies scenario,significant reductions in daily lowtemperatures occur across a more spatiallyexpansive zone than in response to anyother scenario. Presented in Figure 3.18,an area equivalent to about 130 squarekilometers, centered on the urban core, andradiating to south, west, and near east zoneso the Metro region experiences an averagereduction in temperatures o 1°F and ashigh as 5°F. While less spatially expansivehotspots persist to the south o the urban

warm season temperatures. As such, eachnew green roo is likely to be more effectivein lowering temperatures overall than eachnew cool roo o equal area. Te challengeor green strategies is in increasing thetotal area subject to green conversions ata cost that is comparable to cool materialsconversions. Another important variable to

consider is the potential synergistic coolingeffect rom the combination o both coolmaterials and greening approaches. Tiskey finding is explored in Section 3.3.5.

3.3.4 Energy Efficiency Scenario: TeEnergy Efficiency scenario assumes thequantity o waste heat emitted rom vehiclesand buildings is reduced by 30 and 35%,respectively, in response to policies limiting

tailpipe emissions over time and reducingthe energy required to cool buildingsduring the summer months. While wasteheat emissions can be a significant drivero elevated temperatures in large, denselypopulated cities, in less dense urbanenvironments, such as Louisville, energyefficiency strategies are likely to achievelower cooling benefits than cool materialsor greening strategies.

Figures 3.15 and 3.16 find the influenceo the Energy Efficiency scenario to bemodest across the Louisville Metro region,with neither the warm season average dailyhigh or low te

louisville heat mgt report_public comment april 2016

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