DISSERTATION Sustainable Architecture 2024

Transformational adaptation of urban neighbourhoods to tackle extreme heat: A case of Delhi’s street markets

Meghana Roy Uragayala | 19272488

Submitted in partial fulfilment of the MSc degree in Sustainable Architecture: Evaluation and Design

Oxford Brookes University 2024

1.1

Statements

This thesis is being submitted to the Department of Architecture at Oxford Brookes University in partial fulfilment of the requirements for the degree of MSc.

This thesis is the result of my own independent work/investigation, except where otherwise stated. Other sources are acknowledged by explicit references.

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1.2 Abstract Urban neighbourhoods are increasingly vulnerable to extreme heat events, posing significant risks to human health, economy, and environment. Delhi, a rapidly urbanizing city, is no exception This dissertation explores the transformational adaptation strategies to alleviate extreme temperatures in dense urban street sections, especially in cities that are majorly occupied by informal sectors. The current gaps in Heat action plans, oversimplified mitigation strategies and lack of climate sensitive urban planning was identified through literature studies.

A street market in Karol Bagh neighbourhood on Ajmal Khan Road, Delhi, was critically studied to propose realistic strategies through a series of simulated strategies aimed at reducing streetlevel temperatures.

By utilizing ENVI-met simulation software model the impacts of urban vegetation, urban surfaces and urban albedo on heat mitigation were evaluated. The results were analyzed in terms of simulation data and their implications on the specific context.

The Recommended strategy, developed from simulation results and practical constraints, proposed a balanced approach including sandstone pavement, retractable sunshades for flexible shading, and strategically placed trees to provide cooling and improve street aesthetics. This combination achieved air temperature reductions of 3.59% and surface temperature reductions of up to 13.4%. While not as effective as the Best Case scenario, which proposed granite pavers, this strategy, offers a more feasible and contextually appropriate solution for the street market, balancing temperature mitigation with local economic and social considerations.

This research underscores the importance of context-specific urban planning strategies to address heat-related challenges in cities. By tailoring solutions to the unique characteristics of individual urban areas, we can create neighbourhoods that are truly resilient to the impacts of climate change.

3| Strategies to tackle extreme heat in Delhi street markets

1.3 Acknowledgements I would like to express my sincere thanks to my supervisor, Michael Spooner, for his invaluable guidance, support, and encouragement throughout this research endeavour. His expertise and mentorship have been instrumental in shaping this dissertation.

I am also deeply indebted to Professor. Rajat Gupta, whose insights and expertise have significantly contributed to the success of this project.

I would like to extend my special thanks to Shahab Resalati, Scott Sworts and other professors for their valuable guidance and teaching throughout this dissertation.

I am grateful to Marcelo Gunther for his generous assistance with the ENVI-met software. His expertise and technical support were crucial for the successful completion of simulations.

Finally, I would like to thank my family and friends for their unwavering support and encouragement throughout this journey. Their belief in me has been a constant source of motivation.

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1.4 Table of contents

2.

3.

1.1

Statements .................................................................................................................... 2

1.2

Abstract ......................................................................................................................... 3

1.3

Acknowledgements ....................................................................................................... 4

1.4

Table of contents ........................................................................................................... 5

1.5

List of Figures ................................................................................................................ 8

1.6

List of Tables ............................................................................................................... 10

Introduction .......................................................................................................................... 11 2.1

Urban Heat and Extreme heat events ......................................................................... 11

2.2

Most vulnerable cities and people ............................................................................... 12

2.3

Delhi’s historic markets at risk ..................................................................................... 13

2.4

Addressing heat in street markets ............................................................................... 14

2.5

Conclusion ................................................................................................................... 15

Literature review .................................................................................................................. 16 3.1 Mitigation strategies .......................................................................................................... 16 3.2

Background and context. ............................................................................................. 19

3.2.1

Extreme Heat in Indian Cities .............................................................................. 19

3.2.2

Heat action plans ................................................................................................. 19

3.2.3 3.2.4 3.3

Case Study: Ahmedabad Heat Action Plan ............................................................ 20 Limitations and gaps in Heat action plans: .......................................................... 21 Delhi: the epicenter of Heat ......................................................................................... 22

3.3.1

Delhi’s weekly street markets .............................................................................. 23

3.3.2

Risks and Vulnerabilities Faced by Street Vendors ............................................ 24

3.3.3

Policy gaps and overlooking urban Interventions ................................................ 25

3.4

Site of Study: Ajmal Khan Road, Karol Bagh .............................................................. 26

3.4.1

Government Intervention in 2019 ........................................................................ 27

3.4.2

Impact of the Pedestrianization ........................................................................... 28

3.4.3

Limitations and issues ......................................................................................... 29

3.5

Conclusion ................................................................................................................... 30

4.1

Research gap .............................................................................................................. 31

4.2

Research questions ..................................................................................................... 31

4.3

Research Aim .............................................................................................................. 32

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4.4 5.

Objectives .................................................................................................................... 32

Methodology ........................................................................................................................ 33 5.1

6.

Research Method ........................................................................................................ 33

5.1.1

Approach: ............................................................................................................ 33

5.1.2

Specific quantitative methods used include ........................................................ 33

5.2

Simulation Parameters ................................................................................................ 34

5.3

ENVI-met ..................................................................................................................... 35

5.3.1

ENVI-met Specifications ...................................................................................... 36

5.3.2

Meteorological Parameters ................................................................................. 37

5.3.3

Levels of data analysis ........................................................................................ 37

5.3.4

Guide to understanding ENVI-met visualization charts ....................................... 38

5.3.5

Data analysis ....................................................................................................... 39

Simulations, results and Analysis ........................................................................................ 40 6.1

Delhi climate ................................................................................................................ 40

6.1.1

Weather ............................................................................................................... 40

6.1.2

Meteorology ......................................................................................................... 41

6.2

Base case and Existing case ...................................................................................... 43

6.2.1

Base case ............................................................................................................ 43

6.2.2

Existing Case ....................................................................................................... 44

6.2.3

Analysis ............................................................................................................... 45

6.3

Strategy testing............................................................................................................ 47

6.3.1

Urban Vegetation ................................................................................................. 47

6.3.1.1 Trees 5m to 10m in height planted 4m apart. ................................................... 48 6.3.1.2 6.3.2

Urban Shading ..................................................................................................... 49

6.3.2.1

Sunshade Sails at 2m...................................................................................... 51

6.3.2.2

Sunshade Sails at 4m...................................................................................... 52

6.3.3

Urban Albedo ....................................................................................................... 53

6.3.3.1

Sandstone Pavement ...................................................................................... 54

6.3.3.2

Granite pavement ............................................................................................ 55

6.3.4 6.4 6.4.1 6.5

Trees 10m to 20m in height planted 8m apart ................................................ 49

Strategies Analysis .............................................................................................. 56 Best case scenario ...................................................................................................... 58 Best case Analysis .............................................................................................. 60 Combination strategies ................................................................................................ 61

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7.

6.5.1

Urban Vegetation + Urban Shading (Without Pavement) ................................... 61

6.5.2

Urban Shading + Urban Albedo (without Trees) ................................................. 62

6.5.3

Urban Vegetation + Urban Albedo (Without Sunshade sails) ............................. 62

6.5.4

Analysis of Combined strategies ......................................................................... 63

Discussion ........................................................................................................................... 65 7.1

Simulation results and Analysis ................................................................................... 65

7.1.2

Temperature Comparison ................................................................................... 66

7.1.3

Simulation Parameters ........................................................................................ 67

7.1.3.1

Wind................................................................................................................. 67

7.1.3.2

Relative Humidity............................................................................................. 69

7.1.4

Percentage reduction in Temperature and Surface Temperature ...................... 71

7.1.5

Night-time Temperatures ..................................................................................... 72

7.1.6

Seasonal behavior of strategies .......................................................................... 73

7.2

Speculations and Implications ..................................................................................... 75

7.2.1

Social and cultural context .................................................................................. 75

7.2.2

Economic Constraints.......................................................................................... 76

7.2.3

Realistic Implementation: .................................................................................... 77

7.2.1

Role of the Government and Policymakers ......................................................... 78

8. Recommendations .................................................................................................................. 79 8.1 9.

Cost- Benefit ................................................................................................................ 82

Conclusion ........................................................................................................................... 83 9.1

Limitations ................................................................................................................... 85

9.2

Opportunities ............................................................................................................... 85

9.3

Next Steps ................................................................................................................... 86

10.

References ...................................................................................................................... 87

11.

Appendix ............................................................................ Error! Bookmark not defined.

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1.5 List of Figures Figure 1-Tropical zones of the world.(source-meteoblue.com); Figure 2- Maximum feels like temperatue (source- theeconomist.com) ....................................................................................................................... 11 Figure 3- Extreme heat vulnerability analysis framework (Wilhelmi and Hayden 2010) .............................. 12 Figure 4a and 4b- Typical old city markets of Delhi .................................................................................... 13 Figure 5- Košir, Mitja. “Bioclimatic Potential — A Way to Determine Climate Adaptability.” In Climate Adaptability of Buildings: Bioclimatic Design in the Light of Climate Change, 2019 .................................... 14 Figure 6- Adapted from NRDC on Ahmedabad heat action plan ................................................................ 20 Figure 7- The percentile the four metropolitan cities (Kolkata, Chennai, Delhi and Mumbai)by P.Kumar, 2022. ........................................................................................................................................................... 22 Figure 8- Land surface temperatures by world resources institute.............................................................. 22 Figure 9- Thermography images captured by Greenspace, 2024 ............................................................... 23 Figure 10- Delhi's weekly markets by WEIGO ............................................................................................ 24 Figure 11- Design for street vendors from urban India street design guide ................................................ 25 Figure 12- MCD plan locating Karol Bagh in Delhi map; Figure 13- MCD intervention area highlighting Ajmal Khan road ......................................................................................................................................... 26 Figure 14a and 14b: Ajmal khan street character mages before 2019; Figure 15- Section of original street (source- MCD submitted to UTTIPEC) ........................................................................................................ 26 Figure 16a and 16b- nilaA collage illustration for proposal; Figure 17- Section of proposed street (sourceMCD submitted to UTTIPEC) ...................................................................................................................... 27 Figure 18- nilaA Ajmal khan street design intervention plan ....................................................................... 28 Figure 19- Images of Ajmal khan post 2019 intervention (MCD)................................................................. 28 Figure 20- Neighbourhood proposal by MCD for Karol Bagh ...................................................................... 29 Figure 21- Methodology flowchart ............................................................................................................... 34 Figure 22- Average Hawker with vending cart (SOurce- Archade AI) ......................................................... 37 Figure 23- Guide to visualize ENVI-met Leonardo visualization chart ........................................................ 38 Figure 24- Typical ENVI-met visualization chart in section ......................................................................... 38 Figure 25- Average mean temperatures with precipitation of Delhi (Sources- meteoblue.com) ................. 41 Figure 26- A closer summer months daily temperatures (Source- weathespark.com) ................................ 41 Figure 27- monthly number of sunny, partly cloudy, overcast and precipitation days (Sourcemeteoblue.com) .......................................................................................................................................... 42 Figure 28- Delhi wind rose diagram (source- envitrans.com) ...................................................................... 42 Figure 29- illustrate the seasonal wind charts to analyze the role of wind on microclimate in depth. ......... 42 Figure 30- Base case spaces model; Figure 31- Base case temperature visualization chart ..................... 43 Figure 32- Existing case spaces model; Figure 33- Existing case temperature visualization chart ............ 44 Figure 34- comparative analysis at ground level; Figure 35- comparative analysis at human height level . 45 Figure 36- Temperature Distribution at Different Heights (3:00 PM) ........................................................... 45 Figure 37a and 37b- Surface temperatures of basecase and existing case ............................................... 46 Figure 38- Spaces model with trees at 5m to 10m height ........................................................................... 48 Figure 39a and 39b- Temperature visualization charts at 0.1m and 1.5m heights ...................................... 48 Figure 40- Spaces model with trees at 10m to 20m height ......................................................................... 49 Figure 41- Temperature visualization chart at 0.1m; Figure 42- Surface temperature chart. ...................... 49 Figure 43a,43b and 43c- Spaces model with sun sails at 2m height .......................................................... 51 Figure 44- Temperature visualization chart at 0.1m .................................................................................... 51 Figure 45a, 45b and 45c- Spaces model with sun sails at 4m height ......................................................... 52 Figure 46- Temperature visualization chart at ground level ........................................................................ 52 Figure 47- Spaces model with Sandstone pavers ....................................................................................... 54 Figure 48- Temperature visualization chart at 0.1m; Figure 49- Surfave temperature chart ....................... 54 Figure 50- Spaces model with Granite pavers ............................................................................................ 55

8| Strategies to tackle extreme heat in Delhi street markets

Figure 51- Temperature visualization chart at 0.1m; Figure 52- Surface temperature chart ....................... 55 Figure 53- Vegetation strategy temperature cases compared at 3 pm ....................................................... 56 Figure 54- Sunshade sails temperature cases compared at 3 pm .............................................................. 56 Figure 55- Urban pavers temperature cases compared at 3 pm ................................................................. 56 Figure 56- Mitigation strategies temperature comparison graph at 3pm ..................................................... 57 Figure 57a, 57b and 57c- Spaces model with combination of vegetation and sunshade sails and pavers . 58 Figure 58a and 58b- Temperature visualization charts at 0.1m and 1.5m heights ...................................... 59 Figure 59- Reflected SW radiation chart; Figure 60- Surface temperature visualization chart .................... 59 Figure 61- Best case and existing case temperature comparison graph at 3 pm ....................................... 60 Figure 62a, 62b and 62c- Spaces model with combination of vegetation and sunshade sails .................... 61 Figure 63- Air temperature visualization chart at ground level .................................................................... 61 Figure 64a, 64b and 64c- Spaces model with combination of sunshade sails and granite pavers ............. 62 Figure 65- Air temperature visualization chart at ground level .................................................................... 62 Figure 66a, 66b and 66c- - Spaces model with combination of granite pavers and vegetation .................. 63 Figure 67- Air temperature visualization chart at ground level .................................................................... 63 Figure 68- combined strategies temperature comparative analysis graph at 3 pm ..................................... 63 Figure 69a, 69b and 69c- Reflected southwest radiation temperatures for all 3 combined strategies respectively ................................................................................................................................................. 64 Figure 70a and 70b- Air temperature visualization in section of Existing case and Best case at 3 pm ....... 65 Figure 71- All simulations temperature result comparison graph at 3pm .................................................... 66 Figure 72a and 72b- Wind speed visualization chart in section for existing case and best case at 3pm .... 67 Figure 73a and 73b- Wind speed and wind direction visualization chart in plan for existing case and best case ............................................................................................................................................................ 68 Figure 74a and 74b- Relative humidity visualization chart in section for existing case and best case at 3pm .................................................................................................................................................................... 69 Figure 75a and 75b-Reflected southwest solar radiation visualization chart in plan for existing case and best case .................................................................................................................................................... 70 Figure 76- All cases temperature comparison at 3 am ................................................................................ 72 Figure 77- All cases day and night temperature comparison graph. ........................................................... 72 Figure 78a, 78b and 78c- Ajmal Khan road street sketches trying to capture its socio-cultural character. . 75 Figure 79a and 79b- Images from 2019 intervention and adaptation of stakeholders................................. 76 Figure 80- Recommending parijat plant (Nyctanthes arbor-tristis) as 5m to10m tall vegetation ................. 80 Figure 81- Recommending Neem (Azadirachta indica)tree as 10m to 20m tall tree plantation .................. 80 Figure 82a and 82b- Recommending white color sails and sandstone pavers (Generated using Adobe AI) .................................................................................................................................................................... 80 Figure 83- Spaces model with vegetation, sunsails and Sandstone pavers ............................................... 81 Figure 84- Graph comparing exisitng case, best case and recommended case temperatures at 3 pm ...... 81

9| Strategies to tackle extreme heat in Delhi street markets

1.6 List of Tables

Table 1- Mitigation Strategies adopted across the world to tackle extreme heat ....................... 17 Table 2- Failed mitigation strategies across the globe ................................................................ 19 Table 3- Base case, Existing case and proposal testing ............................................................ 35 Table 4- ENVI-met specifications ................................................................................................ 36 Table 5- ENVI-met meteorological parameters ........................................................................... 37 Table 6- Base case and Existing case descriptive stratistics ...................................................... 45 Table 7- List of proposed plantation trees ................................................................................... 48 Table 8- List of existing Tarpaulin sheet types with properties ................................................... 50 Table 9- List of proposed Sunshade sails with properties .......................................................... 50 Table 10- List of pavement materials with properties.................................................................. 53 Table 11- Descriptive statistics of strategies tested .................................................................... 57 Table 12- Surface temperature and reflected solar radiation for combined strategies. .............. 64 Table 13- Effect of relative humidity on proposed strategies. ..................................................... 69 Table 14- Framework of strategies with percentage reductions ................................................. 72 Table 15- Speculative strategy response in different seasons. .................................................. 74 Table 16- recommended strategy for site with specfications ...................................................... 79 Table 17- Cost-benefit analysis for proposed strategies ............................................................. 82

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2. Introduction Today, 55% of the world’s population lives in urban areas, a proportion that is expected to increase to 68% by 2050. (UN, 2018). The majority of this population resides in regions near the equator, primarily within tropical climates, which are characterized by high temperatures. Tropical Cities are becoming hotter because heat is trapped near the earth's surface due to a decrease in green cover, rapid urbanization, energy-intensity activities, and concrete structures.

Figure 1-Tropical zones of the world.(source-meteoblue.com); Figure 2- Maximum feels like temperatue (sourcetheeconomist.com)

2.1 Urban Heat and Extreme heat events The added heat stress in cities will be even higher than the sum of the background urban heat island effect and the heat wave effect (Li D, Bou-Zeid E, 2013). The Urban Heat Island effect, a phenomenon where urban areas experience significantly warmer temperatures than their rural surroundings, aggravates the already rising global temperatures. In these areas, extreme heat becomes more than just an environmental issue—it is a matter of public health and equity.

Warmer baseline temperatures in tropic cities are further elevated by extreme heat events (EHEs) or heat waves, which are projected to strike with increasing frequency and intensity in the 21st century (Meehl GA, Tibaldi C, 2004). The distinction between heat waves and extreme heat waves (EHWs) typically lies in the intensity and severity of the temperature anomaly. Both refer to prolonged periods of higher-than-normal temperatures, but extreme heat waves are more intense.

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2.2 Most vulnerable cities and people In 2015, four of the ten deadliest natural disasters occurred by heat waves; in terms of mortality, South Asian heat waves ranked third and fourth (UNISDR,2016). South Asian cities, which are among the most densely populated in the world, are highly vulnerable to heatwaves. In India, for example, the 2015 heatwave claimed over 2,500 lives, making it one of the deadliest heat-related disasters in recent memory (krishnan, 2022).

According to UN DESA, 2018, Delhi is projected to become the most populous city in the world around 2028, crossing Tokyo. Despite its rapid growth, Delhi faces significant challenges including urban sprawl, extreme weather conditions, environmental degradation, and socioeconomic inequalities (Verma & Sharma, 2019).

Recent studies over the past decade have highlighted the urgent need for public health interventions to protect vulnerable populations from heat-related illnesses (Sandink D, 2013).

These studies have identified individuals with direct exposure to high temperatures, including children, the elderly, pregnant women, and those of low socioeconomic status, as being at a substantially higher risk of experiencing heat-related health problems.

Figure 3- Extreme heat vulnerability analysis framework (Wilhelmi and Hayden 2010)

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2.3 Delhi’s historic markets at risk UN’s World cities report, 2022, states that Informality is a reality of urbanization especially in developing countries like India. Markets have long been central to community life and culture, serving as hubs for social and economic exchange for the countries low income groups. Historic markets, such as Delhi's Chandni Chowk, which have thrived for centuries, are now experiencing a downturn in business on hot days as people avoid outdoor spaces to escape the oppressive heat (Ghani, 2020).

Street vendors, hawkers and market workers, who rely on outdoor markets for their livelihood, are particularly vulnerable to extreme heat, when temperatures often soar above 40°C during summer. The informal nature of these markets, combined with inadequate access to cooling infrastructure leaves them exposed to heat stress making them prime vulnerable groups of the city.

Figure 4a and 4b- Typical old city markets of Delhi

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Figure 5- Košir, Mitja. “Bioclimatic Potential — A Way to Determine Climate Adaptability.” In Climate Adaptability of Buildings: Bioclimatic Design in the Light of Climate Change, 2019

Many recent studies compare the vulnerability of neighborhoods within cities, correlating fine scale measurements of microclimate temperatures with neighborhood biophysical and social variables, such as amount of vegetation, open space, and socioeconomic composition of the population (Ruddell DM, 2010).

2.4 Addressing heat in street markets Indian cities have increasingly adopted Heat Action Plans (HAPs) in response to the rising frequency and intensity of heatwaves. These plans, aimed at mitigating the impact of extreme heat, typically include early warning systems, public awareness campaigns, and measures to protect vulnerable populations (Ghosh et al., 2022).

Simultaneously, urban design and development efforts have focused on organizing the chaos of India's bustling street markets, such as through decongestion strategies and infrastructure improvements to facilitate smoother movement and better access to essential services (Ramanathan & Goel, 2020)

.

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2.5 Conclusion In conclusion, the rise of extreme heat in tropical cities presents a significant challenge that demands urgent action. This issue is particularly pressing in cities like Delhi, where extreme heat events affect vulnerable populations, especially those reliant on outdoor markets, such as street vendors and hawkers, who are facing disproportionate risks that is hampers both their health and livelihood opportunities.

While Indian cities have made significant strides by implementing Heat Action Plans (HAPs) and enhancing urban infrastructure, a gap persists between these efforts and the specific needs of street markets. Urban design initiatives often prioritize accessibility and decongestion, but they fail to fully address the heat-related challenges of open-air market environments. The disjointed approach to urban heat mitigation and market design calls for a more comprehensive framework that integrates heat mitigation with the specific socio-cultural and economic context of market spaces.

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3. Literature review This section comprehensively examines existing global mitigation strategies for extreme heat and critically analyzes Indian heat action plans to identify their limitations and pitfalls.

Delhi, identified as the most heat-affected city in India, an attempt to break down its vulnerable street markets is explored. While studying the role of government in the city’s urban interventions, a site is identified as a representative street market to understand the context of this research.

The street analysis along with its recent interventions, its limitations and opportunities are examined as part of the literature, to reveal a significant research gap, which will be the basis of this dissertation, explored in subsequent sections.

3.1 Mitigation strategies From the Introduction, it has been established that the frequency, intensity, and duration of heat waves have been escalating, prompting a need for comprehensive understanding and effective response strategies. Many cities have developed risk management action plans that include mitigation and adaptation strategies to reduce vulnerabilities to climate change (Funfgeld , 2010).

In this section, a few existing mitigation strategies that cities have adopted to tackle urban heat islands and extreme heat events are explored. The idea is to understand the most effective strategies in terms of urban design and heat action plans in a neighborhood context. 

Urban Shading: By employing canopies, sunshade sails, or pergolas, streets and open spaces can be shielded from direct sunlight. These structures reduce surface temperatures by blocking solar radiation, leading to a decrease in air temperatures. Studies by Santamouris, (2011) have shown that sunshades can lower surface temperatures by up to 30-50% and air temperatures by 2-4°C.



Urban Vegetation, particularly tree planting, offers another effective cooling solution. Trees provide shade, reducing direct solar radiation, and also enhance cooling through evapotranspiration. Research by Akbari et al. (2001) has demonstrated that dense canopy cover can reduce surface temperatures by up to 20°C.



Urban Cool Pavements: These pavements utilize materials with higher reflectivity (albedo) to reduce the absorption of solar radiation and lower surface temperatures. Materials such as sandstone, granite, and light-colored concrete can reduce surface temperatures by 10-15°C, resulting in a decrease in air temperature by 1-2°C (Synnefa et al., 2007).

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Strategy

Location of the

Implementation specifics

Reduction

project Urban

New

Vegetation

USA

in

temperatures

York

City,

Planting of street trees and

1.9°C

(Million

creation of urban parks for

temperature

Trees Initiative)

shading and cooling

Melbourne,

Dense

Australia

walkways and public spaces

tree

planting

along

cooler

ambient

Lowered

daytime

temperatures by 2-4°C, reduced

surface

temperature by 20°C Permeable

Chicago, USA

Pavements

Water-permeable allow

heat

pavers

dissipation

to and

2°C reduction in surface temperatures

rainwater absorption Tokyo, Japan

Use of porous materials for

1.5-3°C

cooling

of

paving streets to allow water

surface temperature

infiltration and cooling Shading

Barcelona, Spain

Installation

Structures

(Poblenou

shading structures

(Urban

Superblock)

Canopies)

Dubai, UAE

Cool

Los

Pavements

California

Angeles,

of

large-scale

3-4°C

reduction

pedestrian

in

thermal

comfort Use of canopies, sunshade

2-3°C

sails, pergolas to block direct

temperature

sunlight.

canopies

High

albedo

materials

like

lower

air under

Reduced

surface

sandstone, granite, and light-

temperatures

by

coloured concrete.

15°C, air temperatures

10-

by 2°C Athens, Greece

High-albedo granite used in

2-3°C

reduction

pedestrian zones to reflect

surface temperatures

in

solar radiation Water

Seville, Spain

Features

Installation

of

fountains

or

2-3°C reduction in local

water bodies in public squares

air temperature

Marrakech,

Fountains and water bodies to

1.5-2°C reduction

air

Morocco

cool

temperature

in

through

processes.

evaporative

immediate

surrounding

areas Table 1- Mitigation Strategies adopted across the world to tackle extreme heat

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When implemented in conjunction, urban heat mitigation strategies such as reflective paving, green infrastructure, and shading devices can have a synergistic effect, significantly amplifying the cooling impact by combining the benefits of heat reflection, shading, and evaporative cooling, leading to more substantial temperature reductions and improved thermal comfort in public spaces (Akbari, 2009; Oke., 2017).

To ensure long-term success, strategies must undergo robust evaluation in terms of their climatic performance and adaptability over time. There are a few instances where these strategies have failed over time. A few of them are listed in table 2.

Strategy

Location of the

Overlooked Parameters

Reasons for Failure

Poor species selection led

Chosen plants required high

to higher water demand,

water consumption, creating

making

maintenance challenges in a

project Urban

Cairo, Egypt

Vegetation

Sydney, Australia

maintenance

unsustainable in the long

low-water-availability

run.

environment

Trees were planted without

Poor tree placement trapped

considering wind patterns,

heat and disrupted airflow,

leading to unintended heat

making some shaded areas

accumulation.

hotter rather than cooler

Cool

Ahmedabad,

Dust accumulation on high-

Cool

pavements

became

Pavements

India

albedo surfaces reduced

ineffective due to dust build-

reflectivity, making them

up, reducing their reflectivity

less effective.

and cooling potential

Johannesburg,

High upfront costs and

Limited budget allowed for

South Africa

inadequate funding led to

only partial implementation of

incomplete

reflective

implementation.

diminishing

materials, their

overall

effectiveness Shading Structures

Accra, Ghana

Shading

structures

Fixed

shading

structures

disrupted informal markets

obstructed

and social gatherings.

street vendors and informal activities,

pathways

reducing

for

their

usability and acceptance

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Water

Dubai, UAE

features

Water

features

installed considering

were

Inadequate maintenance and

without

water shortages during the

maintenance

and water scarcity.

dry

season

made

water

features ineffective and costly to maintain

Table 2- Failed mitigation strategies across the globe

These failures highlight the importance of considering local environmental, social, and economic factors when implementing heat mitigation strategies. Without thorough evaluation of site-specific conditions and ongoing maintenance, even well-established strategies may underperform or fail altogether.

3.2 Background and context.

3.2.1

Extreme Heat in Indian Cities

India's rapid urbanization presents an additional layer of complexity to the heat crisis. The urban population is expected to reach 600 million by 2031, accounting for about 40% of the country’s total population (Kundu, 2011). This rapid growth has led to a surge in the number of dense urban streets, characterized by high population density, congested road networks, and mixed land-use patterns. While these streets are vibrant centers of economic activity, they are also major contributors to challenges that worsens the UHI effect.

3.2.2

Heat action plans

To combat the rising threat of heatwaves, Heat Action Plans (HAPs) have been developed as a critical urban adaptation strategy. HAPs are frameworks designed to minimize the health impacts of extreme heat and generally include the following components: 

Early Warning Systems: These systems provide timely alerts about impending heatwaves, allowing government agencies and the public to prepare.



Public Awareness and Outreach: Information campaigns to educate citizens about the risks of heat exposure and measures they can take to protect themselves.



Inter-Agency Coordination: Ensures collaboration between municipal authorities, disaster management agencies, and healthcare providers.



Healthcare System Strengthening: Training for healthcare professionals to recognize and treat heat-related illnesses.

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

Targeted Interventions: Special provisions for vulnerable populations, such as the elderly, children, and outdoor workers.

3.2.3

Case Study: Ahmedabad Heat Action Plan

The Ahmedabad Heat Action Plan (AHAP), introduced in 2013, was South Asia’s first comprehensive heat adaptation framework, designed to mitigate the effects of extreme heat. It was developed in response to the deadly heatwave of 2010, during which the city experienced temperatures as high as 47°C, resulting in over 1,300 excess deaths (Azhar et al., 2014).

Figure 6- Adapted from NRDC on Ahmedabad heat action plan

The plan is a collaboration between the Ahmedabad Municipal Corporation (AMC), Indian Institute of Public Health, and Natural Resources Defense Council (NRDC), and has since become a model for other cities across the country.

The AHAP operates in four distinct phases: 1. Pre-Heat Season: Focuses on training healthcare professionals, launching awareness campaigns,

and

improving

coordination

between

agencies.

Public

service

announcements.

2. Early Warning and Heat Season: This phase includes monitoring temperatures and issuing heat alerts to the public through media and SMS alerts. Special advisories are also issued to vulnerable populations, including street vendors, outdoor laborers, and slum dwellers.

3. Intervention During Heat Events: During heatwave days, cooling centers are established, and temporary shelters with water and shade are provided. The health system is on high

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alert, with additional staffing and emergency services ready to respond to heat-stress cases.

4. Post-Heat Season: Involves data collection and evaluation of the effectiveness of interventions, allowing for improvements in subsequent years.

The AHAP has been credited with reducing heat-related deaths in the city.

The National Disaster Management Authority (NDMA), recognizing the growing threat of heatwaves, issued national guidelines in 2019 to help cities prepare their heat action plans. These guidelines emphasize building capacity within local governments, developing early warning systems, and ensuring public engagement and outreach during heatwave events (NDMA, 2019).

3.2.4

Limitations and gaps in Heat action plans:



Lack of Comprehensive Coverage and Limited Geographic Implementation



Inadequate Funding and Resources



Weak Monitoring, Evaluation and data collection



Overlooked Vulnerable Populations.



Lack of implementation of passive mitigation strategies



Urban Design Oversights



Lack of public awareness

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3.3 Delhi: the epicenter of Heat Among Indian cities, Delhi stands out as one of the most affected by extreme heat, from a study

by P.kumar (2022), where four most populous Indian cities, Chennai, Kolkata, Mumbai and Delhi, are studied to analyze heat stress on the city.(figure 7).

Figure 7- The percentile the four metropolitan cities (Kolkata, Chennai, Delhi and Mumbai)by P.Kumar, 2022.

The city’s geographic location combined with high levels of vehicular emissions and dense urban fabric, has consistently recorded some of the highest temperatures in India, often exceeding 48°C during peak summer months. The land surface temperature maps of Delhi (figure 8), as highlighted in recent studies, reveal widespread heat hotspots, with temperatures in some areas crossing 50°C (World Resources Institute, 2022). This combination of extreme heat and poor air quality has severe implications for the city’s residents, particularly for vulnerable populations and low-income communities.

Figure 8- Land surface temperatures by world resources institute

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Growing thermal discomfort in Delhi streets is mapped by Greenpeace India and National Hawkers Federation by capturing real-time condition of street vendors using thermal camera for the summer of 2024. The thermal images (figure 9) show that street vendors are working at 50 °C. to earn their livelihood. .

Figure 9- Thermography images captured by Greenspace, 2024

According to the World cities report, Informality is a reality of urbanization especially in developing countries. Cities will not be able to offer a bright urban future if their informal sector workers are perpetually excluded from urban development processes. (UN, 2022).

3.3.1

Delhi’s weekly street markets

Delhi, is renowned for its vibrant street markets that cater to millions of residents and tourists alike. Markets such as Chandni Chowk, Sarojini Nagar, and Karol Bagh have historically been essential to the city’s economy and social fabric, offering a diverse range of products, from textiles to street food. Street markets, especially in densely populated cities like Delhi, serve as economic lifelines for various groups, including informal vendors, small traders, and low- to middle-income shoppers.

Moving markets that are set up in different locations on different days of the week provide a source of employment for a large number of vendors in the city as mapped by WEIGO in figure 10.

More than 112,500 vendors in Delhi are associated with weekly markets. These markets operate along footpaths or open grounds of residential neighborhoods and are an important source for everyday essentials for middle and low-income communities.

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Figure 10- Delhi's weekly markets by WEIGO

3.3.2

Risks and Vulnerabilities Faced by Street Vendors

As the thermographic images demonstrate (figure 9), vendors work in open environments with little to no shade, leaving them exposed to direct sunlight and extreme surface temperatures. This not only affects their health but also impacts their productivity and overall well-being.

These health risks are exacerbated by the socio-economic vulnerabilities of the vendors. Many come from low-income backgrounds and cannot afford to take time off during heat waves, as their daily earnings are essential for their survival. Additionally, the informal nature of their work means that they often lack access to basic amenities such as drinking water, healthcare, and resting spaces, further increasing their vulnerability to extreme heat.

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3.3.3

Policy gaps and overlooking urban Interventions

In recent years, the Indian government has implemented various initiatives aimed at improving the working conditions of street vendors. The Street Vendors (Protection of Livelihood and Regulation of Street Vending) Act, 2014 was introduced to provide vendors with legal protections.

More recently, the Prime Minister’s Vendors Atma Nirbar Nidhi and initiatives by the National Hawker Federation have sought to formalize the vendor economy by offering financial support and urban design guidelines (figure 11).

Figure 11- Design for street vendors from urban India street design guide

These design proposals figure, offer little to no consideration for shading or heat mitigation strategies. The design blueprints emphasize the construction of elevated platforms and organized vending spaces but fail to incorporate basic heat mitigation measures such as shaded structures, cooling materials, or vegetation.

This reflects a broader policy gap where urban planning efforts prioritize economic and spatial efficiency over environmental resilience. As Jain and Singh (2022) argue, urban design in India has often neglected the impacts of climate change, with limited attention given to cooling strategies in public spaces.

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3.4 Site of Study: Ajmal Khan Road, Karol Bagh Ajmal Khan Road in Karol Bagh, one of Delhi’s most bustling shopping districts, presents an ideal case for studying the intersection of urban planning, pedestrianization, and economic resilience.

Figure 12- MCD plan locating Karol Bagh in Delhi map; Figure 13- MCD intervention area highlighting Ajmal Khan road

Before 2019, this road was a chaotic commercial artery marked by heavy vehicular traffic, overcrowded sidewalks, and an informal economy heavily reliant on street vendors. With limited space for pedestrians, the road saw frequent traffic jams and low air quality, further exacerbated by the dense urban heat island effect in summer months (NDMC, 2019).

Figure 14a and 14b: Ajmal khan street character mages before 2019; Figure 15- Section of original street (source- MCD submitted to UTTIPEC)

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3.4.1

Government Intervention in 2019

The North Delhi Municipal Corporation (NDMC) launched a pedestrianization project in 2019 to decongest the area. This intervention included transforming 600 meters of the street into a pedestrian-only zone, installing benches, adding flower pots. Bollards were placed at entry points to restrict vehicular access, and dedicated spaces were marked for vendors (NDMC, 2019; Business Standard, 2019).

Figure 16a and 16b- nilaA collage illustration for proposal; Figure 17- Section of proposed street (sourceMCD submitted to UTTIPEC)

The primary goals of this project were to encourage walking, improve the shopping experience, and reduce the overwhelming vehicular congestion. The foot path was widened with sandstone pavers (figure19) The roads were clearly demarcated using paint indicating pedestrian vendor, vehicular, seating and plant lanes. Off-street parking spaces were also created nearby to accommodate vehicles. The intervention was seen as a move towards creating more organized and pedestrian-friendly commercial spaces, similar to efforts seen in other parts of the city (Business Standard, 2019).

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Figure 18- nilaA Ajmal khan street design intervention plan

Figure 19a and 19b- Images of Ajmal khan post 2019 intervention (MCD)

3.4.2

Impact of the Pedestrianization

The pedestrianization of Ajmal Khan Road has led to several improvements, including: •

Average reduction of PM 2.5 particles by 35%.

•

Increase in pedestrian traffic by 2.7 times.

•

Increase in sales by 25% to 30%.

•

Basic amenities installed for vendors and shoppers.

•

Safer and reduction in crime.

•

Demarcation of road removed clutter and chaos.

•

Reclaiming spaces lost due to vehicles and parking.

•

Overall character of street improved.

This shift is particularly significant given the city's ambitious goals for sustainable urban mobility (NDMC, 2019).

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Figure 20- Neighbourhood proposal by MCD for Karol Bagh

3.4.3

Limitations and issues

Despite the improvements, the intervention did not adequately address the rising issue of heatwaves in Delhi. The use of traditional asphalt continues to contribute to the urban heat island effect. The intervention completely neglected introducing vegetation on the street due to capital costs and the urgency of the project. The urban planners should know better than just allowing the placement of potted plants.

Although it was a right direction towards managing urban markets, these measures were insufficient to combat` the extreme heat waves that regularly affect Delhi. Informal street vendors, who spend long hours on the road, still face significant challenges related to heat stress and exhaustion during peak summer months (Mishra et al., 2015).

The MDC had proposed extending this model of urban interventions in a few other culturally significant markets such as Krishna Nagar market, Lajpat Nagar market and Kamla nagar market.

It is of utmost importance that they realise the pitfalls of this model in addressing the issues of heat vulnerable groups and must incorporate climate adaptation strategies for their future projects.

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3.5 Conclusion As global climate change intensifies, extreme heat events in Delhi are projected to increase in both frequency and intensity (Murari K.K, 2015; Rohat, 2020). Delhi’s Informal settlements and low-income groups are particularly at risk, as they often lack access to adequate housing, air conditioning, and reliable water supplies. These socio-economic factors, combined with the city's climate, make Delhi one of the most heat-vulnerable megacities in South Asia (Mora C., 2017).

The pedestrianization of Ajmal Khan Road in Karol Bagh represents a significant step toward improving urban liveability in one of Delhi’s busiest commercial districts. However, the current design falls short of addressing the rising threat of heatwaves, which continue to affect the health and livelihood of street vendors and shoppers alike.

As a result, there is an urgent need for comprehensive heat action plans and climate-adaptation strategies to mitigate the impacts of extreme heat on Delhi's population (Singh R.P, 2021).

However, the Delhi Heat Action plan like every other HAP in India does not identify these informal sectors of the city who are equally vulnerable. Future urban planning efforts must incorporate climate resilience strategies to fully address the complex needs of all stakeholders involved in the city’s bustling street markets.

It is crucial to understand implications of the mitigations strategies proposed to look beyond design. .As temperatures continue to rise and urban populations grow, adaptive design approaches that can be tailored to specific site conditions will be crucial for mitigating extreme heat in cities across the world (Santamouris, 2011).

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4.1 Research gap

1. Over simplified strategies that are not Context specific.

Heat mitigation strategies have often been oversimplified as a universal solution, neglecting the importance of contextual specifics like climate, design, socio-cultural factors and other critical variables.

2. Lack of Integration Between Urban Design and climate Adaptation Existing urban design strategies for mitigating heatwaves often focus on aesthetics and spatial organization but lack a robust integration of heat resilience, particularly for vulnerable groups like street vendors.

3. Ineffectiveness of Heat Adaptation Studies Current Heat Action Plans in many cities, especially in developing countries, do not adequately account for informal sectors and overlook vulnerable populations.

The dynamic nature of street markets necessitates tailored solutions that go beyond traditional urban heat mitigation measures.

4.2 Research questions 1. What are the most effective heat mitigation strategies tailored for Delhi’s street markets?

2.

How can urban heat mitigation strategies be effectively contextualized to address the unique characteristics and challenges of Delhi street markets?

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4.3 Research Aim To investigate and evaluate context-specific strategies for mitigating extreme heat in heat vulnerable cities, with a focus on street markets of Delhi, and to develop actionable recommendations for enhancing urban resilience among urban informal sectors.

4.4 Objectives 1. Understanding existing literature on heat mitigation strategies and the its impact on dense urban street markets: •

Conduct a comprehensive review of literature and case studies to identify the limitations of current heat mitigation strategies, heat action plans and government design interventions in urban contexts.

•

Identify focus group of study, site of study, their key vulnerabilities and limitations in extant literature to disclose research gap.

2.

Develop and Test existing street conditions to identify context-specific strategies •

Analyze meteorological data and street-level data to evaluate the effectiveness of recent interventions.

•

Through ENVI-met software, identify required testing parameters and specifications necessary for proposing strategies.

3. Propose mitigation strategies, compare and analyse most effective strategy to present a framework of temperature reductions.

•

Propose and evaluate a range of strategies discussed in literature to quantify their performance in given specific street and for Delhi climate.

•

Utilize ENVI-met simulation results to conclude the effectiveness of these strategies for the given parameters in conjunction with each other and summarise percentage temperature reductions.

4.

Reviewing and discussing simulation results in concurrence with context specific speculations and Implications to recommend the best strategy for the street.

•

Re-examining if the effective simulation strategies are appropriate for the tested street when environmental, economic, and social challenges are addressed.

•

Proposing an evidence-based recommended strategy by assessing scalability and costbenefit for policymakers and urban planners to aid them reciprocate the model in similar settings.

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5. Methodology This section outlines the research approach, underlying principles, and practical methods employed. It also details the specific methods and tools used to conduct the research.

Furthermore, it explains how the collected information was analyzed and synthesized to draw conclusions that align with the previously outlined aims and objectives.

5.1 Research Method the research primarily employs a quantitative approach, utilizing literature review, computer modeling and data analysis to investigate the impact of heat mitigation strategies.

5.1.1

Approach:

The methodology for this research follows a systematic approach, starting with an extensive literature review and subsequently data collection. Due to the distant location of the study site, on-site field study was omitted and all data was acquired from verified online sources. Following this, the ENVI-met software model was utilized to execute simulations, from which results were analyzed and compared to draw conclusions and propose a framework.

5.1.2 •

Specific quantitative methods used include:

Literature Review: A systematic review of existing literature on heat mitigation strategies, urban heat islands, and the impact of extreme heat on street markets.

•

Data Collection: Collection of meteorological data (e.g., temperature, humidity, wind speed, solar radiation) from delhi weather station data sources and street-level data (e.g., building characteristics, vegetation, road infrastructure) using publicly available datasets and existing field surveys.

•

Computer Modeling: The use of ENVI-met software to create digital models of the study area, simulate microclimatic conditions under different scenarios and extract data on relevant parameters.

•

Statistical and comparitive Analysis: Graphs were drawn from statistical analysis of the simulation results to identify trends, patterns, and significant differences. This involved calculating mean, minimum, maximum and range for different variables.

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Figure 21- Methodology flowchart

5.2 Simulation Parameters From Site of study section in Literature review, the testing can be performed as: 1. Base case: The street character before 2019 2. Existing case: The current street post government intervention in 2019 3. Proposal: Exploring mitigation strategies by testing.

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Table 3- Base case, Existing case and proposal testing

The 600m long street with building facades, building roofs, building heights, existing shading vegetation and roads are modelled to the best of knowledge referring from google earth, government websites, cad mapper, GIS and Photographs.

For consistency across all the simulation cases, the width of the street, Buildings and their façade materials are kept constant since the aim is to understand how vegetation, shading and albedo make a difference without making any changes to building fabric. The ultimate goal is to recommend strategies that will improve the environmental conditions for street vendors and pedestrians.

5.3 ENVI-met ENVI-met is a three-dimensional software designed to simulate and analyse the urban environment's microclimate. It calculates the dynamics of microclimatic conditions over a diurnal cycle by modelling the interactions between the built environment, vegetation, and atmosphere.

This software allows for the evaluation of key environmental variables such as air temperature, humidity, wind speed, wind direction and flow, surface temperatures, solar radiation, and pollutant dispersion (Perini & Magliocco, 2014; Yang, 2021). ENVI-met will be used to assess the current impact of urban development on the microclimate of Ajmal Khan road through comparative analysis with the original street prior 2019.

ENVI-met will be used to understand and assess the best strategies in order to effectively mitigate the impact on the street’s microclimate by adding vegetation, altering pavement surfaces and introducing better shading; for instance, these strategies include optimizing vegetation placement

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to lower surface temperatures (Darmanto et al., 2019), as well as the use of cool materials to minimize heat absorption and radiation in urban areas (Santamouris et al., 2020). By simulating these interventions, ENVI-met provides insights into the most effective measures to mitigate urban heat islands and enhance thermal comfort in both neighbourhoods.

5.3.1

ENVI-met Specifications

The modelling specifications listed in table 4, are used in ENVI-met simulations are crucial for accurately obtaining the microclimate results for various parameters (table 5). These input specifications include, weather data, modelling of the street with accuracy in terms of street width, orientation, building heights, materials, vegetation etc.

1. Modelling Software version

5.5.1 winter23

Computation domain

150 X 250 X 50 m

Basic cell size

2m(dx) X 2m(dy) X 2m(dz)

2. Weather data Weather file

epw

file

sourced

from

Meteorological dept. of Delhi Weather station

Central Safdargunj, New Delhi, India

Simulated weather

18th May 2024 (Hottest heat wave day)

3. Simulation work space Modelling of the street

ENVI-met spaces

Simulation input

ENVI-guide

Simulations

ENVI-Core

Data Visualization

Leonardo

Material properties

DB Manager

Table 4- ENVI-met specifications

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5.3.2

Meteorological Parameters

Table 5- ENVI-met meteorological parameters

5.3.3

Levels of data analysis

Hawker head level Ground level (0.1m) Human Height level (1.5m) At 5m At 7m

Hawker feet level

At 10m Figure 22- Average Hawker with vending cart (SOurce- Archade AI)

The data from ENVI-met can be analyzed at different heights. For this report’s simulations, since the aim is to test how people on the streets are affected, the parameters in table 5, are analyzed specifically at Hawker feet and head level as illustrated in figure 22.

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5.3.4

Guide to understanding ENVI-met visualization charts

Throughout this report, to analyze and compare the variable parameters such as temperature, ENVI-met Leonardo is used. Figure 23 illustrates a typical 2D plan and briefs out how to read the chart.

Figure 23- Guide to visualize ENVI-met Leonardo visualization chart

Figure 24- Typical ENVI-met visualization chart in section

For instance, the provided ENVI-met chart in figure 24, represents a cross-section of a simulated urban environment, showing the distribution of air temperature across the area. The color gradients and patterns within the chart provide clues about the temperature variations. The legend adjacent to the chart helps correlate colors with numbers, thus helping the reader identify potential hot spot areas.

Similarly, charts can be compared at different times and levels with different specifications and variables to analyze how microclimate behaves at different points.

It is crucial to remember that for this particular report, as mentioned in the table 4, each grid cell is measures 2m(dx) X 2m(dy) X 2m(dz). This is the common scale that shall be followed throughout.

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5.3.5

Data analysis

To effectively analyze ENVI-met Leonardo visualization data, The results are exported as CSV files or shape files and imported into appropriate data analysis software (Microsoft Xcel). By performing descriptive statistics, correlation analysis, spatial analysis, and time series analysis, valuable insights from the data can be identified.

These analyses can help understand the distribution of variables, identify relationships between different factors, and evaluate the impact of heat mitigation strategies within the simulated urban environment.

Average Temperature Reduction Calculation For the main framework, Air temperatures and surface temperatures are compared to identify the most effective strategy. The percentage reduction is calculated by the following formula: Temperatures of each grid cell (2m X 2m) are averaged to obtain the Parameters (Air Temperature, Radiation, Surface temperature) of the whole street for each simulation scenario. 𝑇 𝑏𝑎𝑠𝑒𝑐𝑎𝑠𝑒 − 𝑇 𝑚𝑖𝑡𝑖𝑔𝑎𝑡𝑖𝑜𝑛 𝑠𝑐𝑒𝑛𝑎𝑟𝑖𝑜 𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑟𝑒𝑑𝑢𝑐𝑡𝑖𝑜𝑛 = ( ) 𝑋 100 𝑇 𝑏𝑎𝑠𝑒𝑐𝑎𝑠𝑒

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6. Simulations, results and Analysis 6.1 Delhi climate Delhi's climate is classified as a Tropical, semi-arid (Köppen climate classification: BSh) with distinct seasonal variations marked by extreme temperatures. Situated in northern India, the city experiences three main seasons: summer, monsoon, and winter.

6.1.1

Weather

Delhi’s geographical position subjects it to distinct seasonal extremes, with cold winters influenced by chilling winds blowing down from the Himalayas and extremely hot summers amplified by dry winds from the Thar Desert to the south. These seasonal winds contribute to Delhi’s exposure to severe heat waves, particularly during the peak summer months from late April to early July, until the onset of the monsoon season provides some respite (Kumar R., 2017; Singh, 2021).

Summers, which extend from April to June, are characterized by scorching heat, with temperatures often exceeding 40°C placing significant stress on the city's population and infrastructure (Pai et al., 2013).

Monsoon season, from late June to September, brings relief from the heat with heavy rainfall.

Delhi receives an average of 700-800 mm of rainfall annually, primarily during the monsoon, but recent trends suggest variability in precipitation patterns due to climate change (Ramanathan et al., 2015).

Winters, from November to February, are relatively mild but can witness sharp drops in temperature, with night time lows often reaching around 4°C.

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6.1.2

Meteorology

Figure 25- Average mean temperatures with precipitation of Delhi (Sources- meteoblue.com)

The average mean temperatures in Delhi ranges between 14C and 33C. The "mean daily maximum" shows the maximum temperature of an average day for every month for Delhi.

Likewise, "mean daily minimum" shows the average minimum temperature. Hot days and cold nights (dashed red and blue lines) show the average of the hottest day and coldest night of each month in figure 25.

Figure 26- A closer summer months daily temperatures (Source- weathespark.com)

The figure 27 illustrates the number of sunny days with temperature ranges on x-axis. More than 15 days of temperatures above 40C is observed in May.

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Figure 27- monthly number of sunny, partly cloudy, overcast and precipitation days (Source- meteoblue.com)

Figure 28- Delhi wind rose diagram (source- envitrans.com)

The wind rose for Delhi indicates that the most frequent wind direction is from the west-northwest (WNW) and northwest (NW). The prevailing wind speeds are generally between 0.5-1 m/s, with lower frequencies of higher wind speeds. There are also notable occurrences of winds from the southwest (SW) and east-northeast (ENE) directions. Overall, the wind rose suggests a predominantly westerly wind pattern in Delhi, with moderate wind speeds being most common.

Figure 29- illustrate the seasonal wind charts to analyze the role of wind on microclimate in depth.

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6.2 Base case and Existing case From Methodology, simulations were run for each case and are analyzed based on the data generated by ENVI-met for 18th May 2024. The analysis focuses on Potential Air Temperature as primary parameter while additional metrics such as Surface temperature and Reflective solar radiation are studied to understand how the grid cells are reacting to strategies. Other parameters such as Relative Humidity, Wind speed are studied in conjunction.

6.2.1

Base case

The base case simulation reflects the street conditions before the 2019 intervention. The 600meter stretch of Ajmal Khan Road is modelled in asphalt, a material with a low albedo ranging between 0.12 to 0.15. existing neighbourhood vegetation with no greenery on the street itself, and the primary shading technique used by the shops and hawkers at ground floor being Tarpaulin sheets of varying low quality are modelled for the base case as shown in figure 30.

Figure 30- Base case spaces model; Figure 31- Base case temperature visualization chart

The temperature data for this case reveal the significant influence of solar orientation and street alignment, with temperatures peaking in the mid-afternoon. Across the day, there is a noticeable peak around 2:00 to 4:00 PM, with direct solar radiation from South-West. This gives us a picture of the building shadow path falling on street.

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6.2.2

Existing Case

For the existing case simulation, the whole 600m of Ajmal Khan road post 2019’s intervention is modelled as a part of the MCD intervention, the whole street was partially pedestrianized with sandstone and lime stone pavers along with Asphalt road. Although the proposal plans proposed tree plantation, only potted plants were placed at 10m apart as seen in figure 19a. The same is modelled for this case with no change in shading as seen in figure 32.

Figure 32- Existing case spaces model; Figure 33- Existing case temperature visualization chart

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6.2.3

Analysis

Figure 34- comparative analysis at ground level; Figure 35- comparative analysis at human height level

The figure 34 compares the base case and existing case temperatures at ground level and figure 35, shows temperatures at human height, throughout the day, from 10:00 AM to 8:00 PM.

At Ground level

At Human Height

Temperature

Base Case

Existing Case

Mean

42.8C

42.4 C

Minimum

39.25 C

38.94 C

Maximum

44.52 C at 3 p.m.

45.66C at 3 p.m.

Range

5.27 C

5.33 C

Mean

41.98

41.96

Minimum

38.50 C

38.59 C

Maximum

44.32 C at 3 p.m.

44.23 C at 3 p.m.

Range

5.82

5.64

Table 6- Base case and Existing case descriptive statistics

From the descriptive statistics Table 6, a slight reduction of 0.4°C due to the pedestrianization efforts by the government is observed. The Temperatures are slightly better at vendor height level.

Figure 36- Temperature Distribution at Different Heights (3:00 PM)

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The graph presents temperatures at different heights at 3:00 PM, showing the vertical heat profile of the street. Both cases exhibit a cooling trend as height increases. For Base Case, at ground level (0.1m), the temperature is 44.60°C, which decreases to 43.65°C at 9m and for Existing Case, the temperature starts at 44.20°C at 0.1m and declines to 43.60°C at 9m.

Figure 37a and 37b- Surface temperatures of base case and existing case

The surface temperature charts from figures 37a, b, depict no noticeable change with similar minimum temperature of 30C, while there is a 1.47C reduction in maximum temperatures. This confirms that the interventions made by Delhi Municipal corporation’s urban design projects are heading towards the right direction unintendedly.

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6.3 Strategy testing For the strategy testing, a section of the street junction is considered. This part of the street has buildings ranging from 4m to 16m in height. The width of the street varies from 18m to 20m. For the modelling of strategies, the existing road with partial pavement and asphalt road is chosen.

All the improvements in terms of vegetation, shading and Albedo are implemented to the existing case. The analysis and comparison of their performance is calculated in comparison to this case.

6.3.1

Urban Vegetation

Based on insights from literature reviews and case studies, introducing vegetation along Ajmal Khan Road has the potential to substantially improve the street environment by offering shade, enhancing air quality, and elevating the overall ambiance. To assess the temperature reductions achieved by different types of vegetation, two scenarios are simulated. At ground level, a 4m x 4m patch with 1m tall hedges/grass is modeled, with the following variations: a) Trees 5m to 10m in height are planted 4m apart. b) Trees 10m to 20m in height are planted 8m apart.

From Delhi Development Authority (DDA) Urban Greening Guidelines (2021), and Tiwari, P., & Thakur, B. R. (2020), a variety of tree species suitable for urban environments have been identified in the table 7, specific to the site Climate based on their height, leaf type, and recommended plantation distance. These native trees are well-suited for street plantation in Delhi due to their ability to tolerate high temperatures, limited water availability, and urban pollution (Trane, M, 2024). Deciduous species help in reducing heat during summer by shading streets and shedding leaves during winter to allow sunlight. Evergreen species provide year-round greenery, adding to both the aesthetic and cooling effects.

Tree Name

Height

Leaf Type

Ideal Climate

Plantation

Range Indian

Laburnum

6-10

(Cassia fistula) White

Frangipani

5-8

(Plumeria alba) Indian Tulip Tree

5-10

Distance semi-

tropical

evergreen

subtropical

semi-

tropical

evergreen

subtropical

Evergreen

tropical

(Thespesia populnea) Amaltas (Cassia fistula)

to

4 – 5m apart

to

4 – 5m apart

to

5m apart

subtropical 5-10

Deciduous

Tropical,

semi-

3 – 4m apart

arid

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Neem

10-15

Evergreen

(Azadirachta indica) Jamun

10-15

Evergreen

5 – 6m apart

Sub-tropical,

4 – 5m apart

humid 10-15

Evergreen

(Ficus religiosa) Arjun

to

tropical

(Syzygium cumini) Peepal

Semi-arid

Tropical to sub-

4 – 6m apart

tropical 10-15

Evergreen

Sub-tropical

5 – m apart

15-25

Evergreen

Tropical,

4

(Terminalia arjuna) Alstonia (Alstonia scholaris)

humid

– 6m apart

to semi-humid

Table 7- List of proposed plantation trees

6.3.1.1 Trees 5m to 10m in height planted 4m apart.

To the existing case, 5m to 10m tall round and dense foliage trees are modelled 4m to 6m apart with 4m X 4m hedges at the foot of the trees that are 1m in height on ENVI-met as illustrated in figure 38.

Figure 38- Spaces model with trees at 5m to 10m height Figure 39a and 39b- Temperature visualization charts at 0.1m and 1.5m heights

From figure 39, Temperatures at ground level and human height can be observed. The minimum and maximum temperatures averaged from the grid cells is 42.74C and 45.85C at 0.1m level and 42.64C and 45.10C at 1.5m level. As expected, the Temperatures decrease as we measure it higher from ground level.

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6.3.1.2 Trees 10m to 20m in height planted 8m apart

Figure 40- Spaces model with trees at 10m to 20m height Figure 41- Temperature visualization chart at 0.1m; Figure 42- Surface temperature chart.

15m tall round and dense foliage trees are modelled 10m to 12m apart with 4m X 4m hedges 4m apart that are 1m in height on the ground level as seen the figure 40.

From the visualization charts, Maximum and minimum Temperatures at ground level are 42.70C and 45.49C. The overall average surface temperature of the modelled street decreased by 2.89C compared to existing case with maximum temperature of 60.97C.

6.3.2

Urban Shading

As the Sustainable Cities and society, 2020, suggests, the potential of sun sails as heat mitigation strategy at a street scale is significant. Testing it for Karol Bagh context could be one of the three mitigation strategies explored.

Existing shading modelled for base case and existing case is self-sourced Tarpaulin sheets usually made of Polypropylene or Polyethylene that have high absorption and low reflection values. Table 8 summarizes different tarpaulin sheet materials from low-grade to high-grade, detailing their properties for heat management gathered from varied sources (Wang, J, 2019,). It is important to note that the properties of these materials vary with thickness and if additional coatings are done (Peng, Y, 2016).

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Table 8- List of existing Tarpaulin sheet types with properties

For the testing, sunshade sails are proposed along the high pedestrian activity street, to help reduce direct solar radiation exposure and quantify the heat reduction.

Table 9- List of proposed Sunshade sails with properties

From the table 9, although the PVC coated sails are of best quality, due to their high cost and maintenance, HDPE sunshade sails are chosen for testing as they are cost-effective and are better than existing PP and PE Tarpaulin sheets. Two simulations are modelled at different heights from ground, to understand which level is best suited: a) Sunshade Sails at 2m b) Sunshade Sails at 4m

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6.3.2.1 Sunshade Sails at 2m Sunshade sails of 2m X 2m are modelled for 16m2 to 24m2 along the street 4m apart at 2m height. The existing Tarpaulin sheets are replaced with HDPE sails. The sails are proposed on either side of the road above the footpath. Since these sails are low in height, they can be extended from building facades, store fronts or erected as part of hawker stalls. The placement of the sunshade sails can be observed in green color on the ENVI-met model in figure43.

Figure 43a,43b and 43c- Spaces model with sun sails at 2m height Figure 44- Temperature visualization chart at 0.1m

From figure 44, Temperatures at ground level and human height can be observed. The minimum and maximum temperatures averaged from the grid cells is 42.73C and 46.07C at 0.1m level and 42.67C and 45.27C at 1.5m level. The results at 2m are similar to 5m to 10m tall trees.

At 2m height, sails are closer to the people and objects beneath them, providing better direct shading and reducing the immediate temperature in the shaded area. But the airflow under the sail is restricted, meaning it could trap some heat even when breathable materials like HDPE are used.

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6.3.2.2 Sunshade Sails at 4m Sails of 2m X 2m are modelled for 16m2 to 24m2 along the street 4m apart at 4m height for this case. Since these sails are now at the height of Electric and light poles, they can be tied or extended from building facades. Some localized issues might arise due to existing wires, poles and other visibility reasons for the sails to be erected at this height and hence the distances and areas covered might be compromised. However, they are neglected and an ideal situation is considered to understand the effect of these shading devices in the given scenario as modelled in figure 45.

Figure 45a, 45b and 45c- Spaces model with sun sails at 4m height Figure 46- Temperature visualization chart at ground level

Figure 46 depicts minimum and maximum temperatures at ground level and human height averaged from the grid cells are 41.95C and 44.25C at 0.1m level and 41.92C and 43.83C at 1.5m level. A difference of almost 2C can be noticed in average from sun sails erected at 2m and 4m height. And from Surface Temperature chart, 0.2C reduction is noticed for the overall street.

It is observed that Installing shade sails at 4m height allows for greater air circulation underneath, which can cool the area more effectively through natural ventilation. While higher sails may not block all direct sun exposure, this height allows for a balance between shade and ventilation that can help reduced heat buildup in the open street market.

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6.3.3

Urban Albedo

Improving pavement is an effective strategy to mitigate the impacts of extreme heat in urban settings (Synnefa, A.,2008) as pavements cover a significant portion of the surface in cities.

Albedo is the fraction of light that is reflected by a surface. By incorporating pavers with higher Albedo and those capable of reducing surface temperatures, the temperatures at ground level can be controlled to alleviate heat stress for the targeted vulnerable groups during peak summers.

Table 10- List of pavement materials with properties

To assess the impact of different pavement materials on the microclimate, sandstone and lightcolored granite were selected for simulation, representing the existing and potentially most effective options.

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6.3.3.1 Sandstone Pavement Ajmal Khan Road's existing 4-meter-wide sidewalks on both sides are paved with red and yellow sandstone pavers. To assess the potential impact of replacing the entire street with sandstone pavers, figure 47 is modelled This scenario would create a fully pedestrianized street, potentially enhancing its social value.

Figure 47- Spaces model with Sandstone pavers Figure 48- Temperature visualization chart at 0.1m; Figure 49- Surface temperature chart

From figure 48, Temperatures at ground level averaged from the grid cells is 41.93C and 43.79C. Simulations indicate that replacing the entire street with sandstone pavers could potentially reduce temperatures by nearly 2C. Sandstone pavers are widely used in Delhi for its availability and aesthetic appeal While it is porous and absorbs heat, it also has the advantage of slowly releasing that heat, which can mitigate the immediate surface temperature rise during peak afternoon hours. However, because sandstone has a relatively low heat reflectivity, it might not be the best.

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6.3.3.2 Granite pavement Granite is highly durable and is extensively used as a building material in India. While Dark coloured granite stone is unsuitable for mitigating heat due to its low albedo and high absorption, light-coloured granite, with an albedo range of 0.4 to 0.6, is one of the best option after concrete pavers for urban footpaths.

Figure 50- Spaces model with Granite pavers Figure 51- Temperature visualization chart at 0.1m; Figure 52- Surface temperature chart

The minimum and maximum temperatures at ground level averaged from the grid cells are 41.78C and 43.74C from figure 52. It is the most effective strategy from all the ones discussed in previous sections Also, from Surface Temperature chart in figure 52, maximum average reduced to 58.160C.

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6.3.4

Strategies Analysis

For the strategies testing, Urban Vegetation, Urban Shading and urban Albedo was simulated and the results have been discussed above.

The adjacent graphs compare simulation results of each strategy.

From

figure

53,

By

introducing

vegetation, 0.76C decrease with 5m to 10m tall trees and 0.54C decrease with 10m to 20m tall trees at ground level is noted,

compared

to

existing

case.

However, when measured higher from the ground level, taller trees were more effective in alleviating the temperatures.

From figure 54, there is 0.2C difference between sunshade sails erected at 2m and 4m. Sails at 4m help decrease the temperatures by 0.9C at ground level.

Clearly, introducing sun sails is one of the economical options.

From figure 55, both sandstone and granite pavers reduce temperatures by 0.97C

and

1.33C

respectively

compared to existing case. Granite paving alone could reduce the ground temperatures by 3.1%.

Figure 53- Vegetation strategy temperature cases compared at 3 pm Figure 54- Sunshade sails temperature cases compared at 3 pm Figure 55- Urban pavers temperature cases compared at 3 pm

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Table 11- Descriptive statistics of strategies tested

Table 11 analyzes the Descriptive statistics for all the six strategies at ground level. A gradual improvement in mean temperatures from vegetation to albedo is evident.

Figure

56-

strategies

Mitigation temperature

comparison graph at 3pm

Figure 56, compares all the strategies discussed in this section. Clearly, sun sails at 2m is the least performing strategy followed by sunshade sails at 4m and trees at 7m height. From the trees at 10m to 20m height trajectory in the graph, it is observed that although the temperature at ground is higher, planting larger trees can improve the overall microclimate by controlling temperatures at foliage level. Sandstone and granite pavements are the most effective strategies. The complexities of implementing these strategies shall be discussed in later sections.

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6.4

Best case scenario (combining all 3 strategies)

Urban heat mitigation strategies, when used in combination, can have a synergistic effect, amplifying their individual benefits (Zinzi, M, 2012). By understanding how each approach influences temperature in the previous section, we can now identify synergy between methods that can maximize cooling effects and test them. Urban vegetation, urban albedo, and urban shading is modelled as the best case scenario for the current street (figure 57).

Figure 57a, 57b and 57c- Spaces model with combination of vegetation and sunshade sails and pavers

For this simulation, the following parameters are modelled: a. Combined Vegetation: Alternate plantation method with both 5m to 10m tall trees and 10m to 20m tall trees with 4m X 4m green surface around them, planted at 4m distance from each other. This way, we can ensure continuous foliage at different heights. All the vegetation is planted on the right side of the street as a part of the original NMDC intervention proposal b. Combined sunshade sails: From the strategy results, clearly 4m high sunshade sails are the most effective. Since a continuous vegetation strategy is being modelled on one side of the street, these sails are restricted to the other side of the road as shown in Green color in figure 57. However, 2m sun sails can still be used between the plantation distances. c.

Pavement: To quantify the highest possible temperature reductions, the best performing pavers, that is, Light granite stone pavers are modelled.

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Figure 58a and 58b- Temperature visualization charts at 0.1m and 1.5m heights

From the potential air temperature visualization charts in figure 58, minimum and maximum temperatures at ground level and human height averaged from the grid cells are 40.46C and 42.45C at 0.1m level and 40.50C and 42.23C at 1.5m level, respectively. From the reflected SW radiation chart (figure 59), amount of radiation reflected by each material used is quantified.

Granite pavement reflects the most radiation ranging from 300W/m2 to 450W/m2. Similarly, from Surface temperature figure 60, the effect of vegetation and sun sails are noticeable.

Figure 59- Reflected SW radiation chart; Figure 60- Surface temperature visualization chart

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6.4.1

Best case Analysis

Figure 61- Best case and existing case temperature comparison graph at 3 pm

For the best case scenario, from the figure 61, we can notice exponential decrease in temperatures compared to existing case. By introducing the most effective vegetation strategy, sun shade sails and granite pavement, the temperatures can be alleviated by 2.18C at ground level and 2.10C at human height which is almost equal. As we move higher, the temperature difference at 9m height is 1.78C, which indicates that the larger temperature difference at ground level is due to reduction of surface temperatures.

Maximized synergy: The reflectivity of albedo surfaces, combined with multi-level shading (from both trees and sails), resulted in the highest reduction in temperatures. Shading from both sails and trees helps limit heat absorption into the reflective surfaces, which already minimize retained heat due to their albedo properties. This combination could be one of the most effective strategy for reducing Urban heat especially in areas with pedestrian traffic and congested urban commercial zones.

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6.5 Combination strategies In this section, a set of two strategies is simulated to quantify and compare the best combination that could maximise temperature reductions. The idea is to provide policymakers and Delhi authorities several options to determine which case will suite the street best. It is important to note that due to computational limitations of the ENVI-met software, all proposed strategies except the base case and existing case were tested only for a 100-meter segment of the road.

6.5.1

Urban Vegetation + Urban Shading (Without Pavement)

Trees and sun sails both provide shading in different ways. Trees offer natural cooling through evapotranspiration, while sails block direct sunlight with less contribution to cooling through transpiration. Together, they can cover a broader range of the urban environment, offering shade at various heights.

Figure 62a, 62b and 62c- Spaces model with combination of vegetation and sunshade sails Figure 63- Air temperature visualization chart at ground level

For this simulation, combination of 5m to 10m and 10 to 20m tall trees with ground level hedges of 1m tall are simulated (same as best case scenario) and Sunshade sails of 16m2 to 24m2 at 4m height on the left part of the street can be observed in different shades of green in figure 62.

The pavement with partial sandstone pavers and asphalt road, from the existing street case is retained in the model.

From figure 63, the minimum and maximum temperatures at ground level averaged from the grid cells are 42.68C and 46.08C. While this combination can lower temperatures by providing extensive shade coverage, the cooling effect at ground level is not effective.

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6.5.2

Urban Shading + Urban Albedo (without Trees)

Sunshade sails block direct sunlight, while albedo surfaces (granite or sandstone) reflect solar radiation. Together, they reduce the amount of heat absorbed by the ground and surfaces below.

For the simulation, Lowest Albedo Granite pavement (0.55) is chosen and shade sails are placed at 4m height on the left part of the street and 2m high sails on right side of the street 4m to 8m apart as shown in white and green in the model figure 64. No trees are introduced except the existing ones on site.

Figure 64a, 64b and 64c- Spaces model with combination of sunshade sails and granite pavers Figure 65- Air temperature visualization chart at ground level

The minimum and maximum temperatures averaged from the grid cells are 42.45C and 45.26C at ground level and 42.42C and 44.78C at human height. from figure 65.

6.5.3

Urban Vegetation + Urban Albedo (Without Sunshade sails)

Vegetation provides shade for pedestrians and vendors and helps control direct solar radiation, while high albedo pavers reflects solar energy, preventing heat absorption into the ground during peak midday temperatures.

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Figure 66a, 66b and 66c- - Spaces model with combination of granite pavers and vegetation Figure 67- Air temperature visualization chart at ground level

For the simulation, granite pavers and trees of varying heights with ground level vegetation same as best case are modelled as depicted in figure 66. For this case, vegetation is only proposed on one side of the street as a continuation of MDC proposal. For best results, Trees can be planted on both side of the street which will further alleviate the overall Ajmal Khan street character.

From figure 67 The minimum and maximum temperatures at ground level averaged from the grid cells are 41.54C and 43.77C. The average temperatures for this case are close to best case scenario.

6.5.4

Analysis of Combined strategies

Figure 68- combined strategies temperature comparative analysis graph at 3 pm

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While introducing better pavers and sun sails show a steady decrease in temperatures with increasing height, the scenarios involving tree plantations show a more pronounced deviation.

Clearly, lowest temperatures at ground level were achieved when cool pavement materials are modelled with 1.85C difference from existing case. The use of sunshade sails adds to the overall reduction of temperatures when combined with Vegetation and pavers. Through combined strategies a maximum of 1.85C, 1.9C, 1.9C, 1.95C can be alleviated at 0.1m, 1.5m, 5m and 9m respectively, from figure 68.

Figure 69a, 69b and 69c- Reflected southwest radiation temperatures for all 3 combined strategies respectively

Table 12- Surface temperature and reflected solar radiation for combined strategies.

Table 12 depicts the reflected SW radiation of the street with combined strategies. A maximum of 761 W/m2 can be reflected by trees and pavers.

Overall, the best performing strategy to control temperatures at ground level and upper levels is by introducing a combination of light colored granite pavers and strategic Vegetation at different heights.

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7. Discussion This section is divided into two parts. In the first part, the simulation results and analysis are critically reviewed and findings are drawn by making a percentage reduction table for temperature, that highlights the most effective strategy in theory according to simulations.

The second section of discussion addresses the context of the site to understand factors that influence the implementation of mitigation strategies. Based on certain parameters like material availability, speculations are listed and a conjecture of findings is produced.

The objective is to correlate findings drawn from simulations and context specific constraints to propose a revised case scenario that would be the best possible option to achieve maximum reductions in temperatures for the Ajmal Khan road.

7.1 Simulation results and Analysis In the previous section twelve simulations were run and analysed: Base case and existing case Analysis Strategies analysis Best case analysis Combined strategy Analysis.

In this section, all the simulations analysis are discussed in concurrence with each other.

Figure 70a and 70b- Air temperature visualization in section of Existing case and Best case at 3 pm

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7.1.2

Temperature Comparison

The graph in figure 71 illustrates all the simulation results at 3 pm at different heights of the street on x-axis and Temperatures on Y-axis. The base case to the best case strategies fall in the range of 3 degrees from 44.5C to 41.50C.

Figure 71- All simulations temperature result comparison graph at 3pm

The following findings are drawn from the graph: 

The temperature reduction generally decreases with increasing distance from ground level.

This suggests that the impact of urban interventions, such as pavers and sunshades, is more impactful at the height at which they are introduced.



Trees, particularly when planted at 15 meters, have a significant effect on temperature reduction and unlike other strategies, they improve the overall microclimate, especially at higher levels where the foliage is well spread out. This slope can be observed in combined strategies where vegetation is introduced.



The type of pavement material used plays a key role in urban settings. The most effective strategy was when pavers were proposed to replace the existing Asphalt road. Granite pavement is the most effective in reducing temperatures compared to sandstone pavement.

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

Sunshades, especially when placed at 4 meters, also contribute to significant temperature reduction, particularly at shorter distances. However, their impact is less pronounced than trees and pavers.



The Best Case scenario, which includes trees, sunshades, and granite pavement, demonstrates the most significant temperature reduction. This suggests that a combination of interventions can achieve optimal results.

7.1.3

Simulation Parameters

Along with the temperature results, to understand why and how the strategies can be implemented in the context and to recommend the best strategies, exploring the rest of the parameters tested by ENVI-met (as mentioned in the table in Methodology) in conjunction to temperature is vital.

In this section, these simulated parameters with respect to most important scenarios such as Existing case, Best case etc., are discussed to draw further findings.

7.1.3.1 Wind From the Delhi climate analysis section, the prevailing wind direction in summer months is between 290 to 340 North-West (Figure 29), at speeds ranging between 1m/s to 5m/s.

Figure 72a and 72b- Wind speed visualization chart in section for existing case and best case at 3pm

From the weather file used for ENVI-met simulations, the average temperature considered for 18th May is 2 m/s. From the wind speed illustrations (figure 72) for existing case and best case,

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at ground level until 2m to 4m height in the street, less than 1 m/s winds are experienced.

Considering a heat wave day, these winds bring little to no relief for pedestrians.

From figure 73, the wind speeds with direction are shown in plan at 1m height. From the flow v legend, it is clear that very little wind enters the streets and when vegetation is introduced, this reduces further.

Figure 73a and 73b- Wind speed and wind direction visualization chart in plan for existing case and best case

When all the wind charts of simulations are analyzed at different heights, it was found that: 

Vegetation at different levels slow down the wind speeds at foliage heights. Wind moving through trees and shaded areas enhances cooling by carrying away hot air, providing relief in urban heat islands. However, with limited wind flow on hot and dry summer days, even the most effective shading or vegetation strategies can only offer localized cooling.



Sunshade sails trap heat due to lack of wind circulation at lower levels especially when installed at 2m height. At 4m height, there is better wind movement which improves air circulation. When heavy winds hit, wind tunnels might form due to the installation of Sun shade sails. It becomes clear that a strategic design is required for planning the spacing, height, angle and location of these sails to maximize thermal comfort that the wind brings.

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7.1.3.2 Relative Humidity Relative humidity (RH) plays a significant role in influencing how heat is perceived in urban settings. High humidity can make heat waves worse and low humidity can possibly help people tolerate heat better. This is due to the heat index effect which affects the thermal comfort of people. The relative humidity levels were under 50% for the simulated heat wave day.

Figure 74a and 74b- Relative humidity visualization chart in section for existing case and best case at 3pm

It is crucial to understand how the amount of humidity in air effects the materials and strategies proposed. Table 13 are the findings from literature review and by analyzing RH charts from different simulations.

Table 13- Effect of relative humidity on proposed strategies.

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For this case, sunshade sails and sandstone pavement are better performing strategy choices.

From figure74b, we can observe increased relative humidity around the vegetation in best case scenario. Surprisingly, granite pavement under performs sandstone when humidity is high due to its non-porous nature.

So clearly, understanding humidity in conjunction with temperatures and material properties is crucial for recommending the best strategy/ combination of strategies.

Figure 75a and 75b-Reflected southwest solar radiation visualization chart in plan for existing case and best case

The results of reflective solar radiation and surface temperatures are already discussed in the previous sections along with the visualization charts. It is clear how each material absorbs and reflects radiation from simulation charts. For reference, the figure 75, depict the base case and best case reflective SW radiation charts. We can visually understand the amount of radiation reflected by sun sails, vegetation and types of surfaces through color coding.

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7.1.4

Percentage reduction in Temperature and Surface Temperature

Based on the simulation results and analysis of Air Temperature, Surface Temperature, and secondary simulation parameters like wind, relative humidity, and solar radiation, the final results with percentage reductions (calculated using the formula outlined in the methodology) are presented in Table 14. The table outlines the design specifications for each scenario, the air and surface temperatures measured at ground level at 3 PM, and the corresponding percentage reductions in temperatures.

Scenario

Existing Case

Model

Ground level

Percentage

Maximum

Percentage

specifications

Temperature

reduction

T Surface

Reduction

at 3 p.m.(̊C)

(%)

.( ̊C)

(%)

Partial

sandstone

pavers

44.27

-

63.86

-

43.51

1.7

61.36

3.9

43.74

1.1

60.97

4.5

Sunshade sails at 2m

43.57

1.5

61.50

3.6

Sunshade sails at 4m

43.41

1.9

60.63

5.0

Sandstone pavement

43.30

2.1

59.82

6.3

Granite pavement

42.94

3.0

58.16

7.9

42.09

4.9

52.20

18.2

42.42

4.1

55.25

13.4

Potted planters Tarpaulin sheets Urban

4m

X

Vegetation

patches

4m

green

5m tall trees 4m

X

4m

green

patches 15m tall trees Urban shading

Urban Pavers

Best

case

Green patches, 7m

Vegetation,

and 15m tall trees

shading

2m and 4m sunshade

pavement

and

sails Granite pavers Without Vegetation

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strategy

Without

combinations

sails Without

Sunshade

42.63

3.7

56.87

10.9

granite

42.95

2.9

57.66

9.7

pavers Table 14- Framework of strategies with percentage reductions

7.1.5

Night-time Temperatures

Throughout the simulation results, only the hottest hour of the day, 3 pm was analyzed and discussed. This is due to the selected niche of the study about proposing strategies to tackle and mitigate extreme temperatures. However, to comprehensively evaluate their effectiveness, examining nighttime performance as well is pivotal. This will help understand if the strategy is worth implementing. The figure 76 presents the temperature data changes 12 hours apart from hottest temperatures (3 AM) and figure 77 illustrates the temperature profile for day and night for 20hours at ground level.

Figure 76- All cases temperature comparison at 3 am Figure 77- All cases day and night temperature comparison graph.

The graphs indicate that the temperatures for most strategies are relatively similar, with variations of less than one degree Celsius, except for the base case. This suggests that the proposed strategies are effective but do not exhibit significant differences during the night. Consequently, it may be reasonable to assume that night-time temperatures have a minimal impact on determining the optimal strategy, as the differences are negligible.

However, if greater precision is desired, specific strategies or materials can be further tested and simulated.

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7.1.6

Seasonal behavior of strategies

Similar to evaluating the effectiveness of proposed strategies for night time, to completely understand their effectiveness, performance throughout the year needs to be studied. Especially for a city like Delhi, being a complex weather region, the city experiences cold winters and unexpected flooding during monsoons apart from scorching summers. While extending the simulation hours to obtain night-time data was feasible, conducting simulations for different seasons was computationally demanding. However, the following table presents a speculative analysis based on existing literature and the simulations conducted so far.

Summer

High Temperatures, Low to Moderate Humidity

(April to June)

Vegetation

Trees will provide crucial shade and evaporative cooling. In low humidity, evapotranspiration will be effective, further cooling the environment and improving thermal comfort for market vendors and shoppers.

Sun Sails

Installing sun sails at higher heights (4 meters) allows better air circulation, which is essential for cooling in this hot, dry period. Shade sails can reduce direct heat exposure, especially in open areas like street markets.

Pavement

Light-colored granite performs best in this season, reflecting significant amounts of solar radiation and keeping surface temperatures lower. Dark granite and asphalt, on the other hand, would exacerbate heat build-up due to high heat absorption and retention.

Monsoon

Hot, Humid and heavy rainfall

(July to Sept)

Vegetation

Vegetation becomes less effective in mitigating heat as evapotranspiration adds moisture to the already humid air, potentially increasing discomfort.

However, the shade from trees remains beneficial in shielding people from direct sunlight.

Sun Sails

Although shade will reduce direct solar radiation, the high RH will limit the perceived cooling benefit. Lowering sun sails to 2m may help keep vendors in more consistent shade.

Pavement

Even highly reflective materials like light granite may not feel as cool due to high RH, which reduces sweat evaporation and increases discomfort. Porous materials like sandstone can provide some cooling via moisture retention, but their heat retention capabilities make them less ideal.

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Winter

Cool to cold, mild sun, Low Humidity

(Nov to Feb)

Vegetation

Trees continue to provide aesthetic and environmental benefits but have a less critical role in heat mitigation during this season.

Sun Sails

hade sails might not be as critical during winter since the solar heat is less intense. However, they can be removed or adjusted to allow more sunlight for warming.

Pavement

Heat mitigation strategies are less crucial during the winter months as temperatures drop. Reflective materials like granite or sandstone are still useful in maintaining a comfortable street surface without generating too much heat.

Table 15- Speculative strategy response in different seasons.

From the above table, notable findings are: 

Granite pavement experiences a significant reduction in albedo properties during the monsoon season due to high relative humidity, while sandstone does not. In contrast, cool pavements are not necessary during winters, making average-performing sandstone a potentially better option.



The changing sun height and path throughout the year render fixed sun sails ineffective.

Retractable sun sails are a more efficient alternative.



Vegetation plays a multifaceted role, and the design proposal to introduce various forms of vegetation, such as grass, hedges, plants, and tall trees, at different levels is beneficial.

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7.2 Speculations and Implications So far, based on simulations and testing, through analysis of data, findings were discussed in the previous section. This section delves into the practical challenges and considerations that must be addressed when implementing heat mitigation strategies in a densely populated, commercialized market like Ajmal Khan Road. It explores the social, cultural, economic, and practical implications of various solutions and cross verify if the design strategies are context specific.

7.2.1

Social and cultural context

Karol Bagh, one of Delhi's most vibrant and culturally significant market areas, is home to a diverse group of street vendors, small businesses, and shoppers from various socio-economic backgrounds. Any urban intervention must respect and support these social dynamics. The proposed interventions need to consider their local customs, daily routines, and traditional uses of space.

Figure 78a, 78b and 78c- Ajmal Khan road street sketches trying to capture its socio-cultural character.

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For example, while sunshade sails can provide significant cooling, their placement, design, and visibility should not obstruct vendors’ stalls or the cultural essence of open-air markets, which rely heavily on visibility and accessibility.

Another critical factor is the perception of materials. Granite, though effective in reflecting heat, may be seen as an upscale material not aligned with the aesthetic of a bustling local market.

Historically, markets in India have utilized materials like sandstone, which is more familiar and culturally ingrained. Thus, sandstone, although absorbing more heat than granite, may be more acceptable to vendors and pedestrians because of its association with traditional urban streetscapes.

Figure 79a and 79b- Images from 2019 intervention and adaptation of stakeholders

7.2.2

Economic Constraints

Economic feasibility is a key consideration, particularly for a market like Ajmal Khan Road, where most stakeholders operate on small budgets.

Granite paving, although theoretically effective, is expensive, while sandstone is more costeffective. The economic difference is significant when paving large areas of a market street, especially given the limited funding available for public infrastructure projects in non-central commercial areas (Planning Commission, 2011).

The Delhi government, through the Smart Cities Mission and National Urban Renewal Mission, has shown interest in upgrading infrastructure in areas like Karol Bagh. Therefore, funding may be available for durable, sustainable upgrades like paving and shading.

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7.2.3

Realistic Implementation: Time Frame, Value, and Maintenance

Implementing heat mitigation strategies in a bustling market like Ajmal Khan street requires careful planning. 

Paving Work: A phased approach over months, could allow for continuous operation of the market, minimizing disruption to the daily flow of business and pedestrian movement while improvements are made.



Sun Sails Installation: The flexibility of sun sails is an advantage. They can be installed relatively quickly and require less disruption. They are also adaptable to be moved or removed if necessary. However, coordination with overhead electric cables, streetlights, and signage would need to be considered to avoid any conflicts with the infrastructure.



Vegetation: Planting trees or integrating greenery requires long-term planning due to the time it takes for trees to mature and provide substantial shading.

Additionally, maintenance is a critical concern. Markets are high-traffic areas, with frequent wear and tear on infrastructure. Granite is more durable but costly to repair when damage occurs, whereas sandstone can be easily replaced or repaired at lower costs. Furthermore, sandstone weathers better in Delhi’s variable climate, particularly during the monsoon when humidity levels rise (Banerjee & Sen, 2013).

Also, due to dust accumulation, high albedo materials might not perform to full potential. So constant maintenance might be required in dry seasons when there is lack of wind and rainfall for self-cleaning.

Sunshade sails, while useful for blocking direct sunlight, require regular upkeep, especially during the monsoon season when heavy rains and winds can damage the sails. The practicalities of cleaning, replacing, and securing the sails would demand a permanent team for maintenance, which might not be economically viable in a busy market with limited government oversight.

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7.2.1

Role of the Government and Policymakers

The Delhi government and local urban planners are increasingly focused on sustainable urban development due to the rising impact of climate change. However, the prioritization of extreme heat mitigation strategies in non-central market streets remains a challenge, as policy often favours central business districts or high-profile areas (Delhi Master Plan, 2021).

For Ajmal Khan Road, government intervention is crucial in providing both policy support and funding for long-term heat mitigation strategies. Collaborative projects between the government and market associations could be instrumental in implementing shading solutions and sustainable pavements. However, given budget constraints and competing priorities, it is likely that lowercost, easily implementable solutions like sandstone paving will receive more support.

Conjecture from the speculations are: 

Prioritize sandstone paving for its cultural relevance, lower cost, and easier installation.

Consider a mix of sandstone and granite in high-traffic areas to balance economic and performance considerations. Implement paving in phases to minimize disruption to market activities.



Install adjustable sun sails in key areas to provide shade without obstructing visibility.

Consider a combination of sun sails and trees for broader coverage and improved aesthetics.

Prioritize areas with high pedestrian traffic for sun sail installations.



Introduce trees in strategic locations to provide shade and improve microclimate. Focus on low-maintenance species that can thrive in urban environments.



Involve local vendors and residents in the design and implementation process.

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8. Recommendations From discussion, most temperature effective strategies from simulations and from speculations, most practical and realistic strategies were identified and the most suitable strategy for the Ajmal Khan road intervention is summarized in table 16.

Table 16- recommended strategy for site with specifications

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To understand the temperature reductions of this recommendation, a simulation with the proposed design specifications is modelled and tested for temperature reductions as depicted in figure 83. Although from discussion it is clear that there shall be restriction for uniform placement of shade sails or vegetation, for consistency with previous results, the same specifications are followed.

Figures 80 and 81, gives an idea of vegetation species chosen for the proposal. More viable options have been discussed in table 7.

Figure 80- Recommending parijat plant (Nyctanthes arbor-tristis) as 5m to10m tall vegetation Figure 81- Recommending Neem (Azadirachta indica)tree as 10m to 20m tall tree plantation

Figure 82a and 82b- Recommending white color sails and sandstone pavers (Generated using Adobe AI)

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.

Figure 83- Spaces model with vegetation, sunsails and Sandstone pavers Figure 84- Graph comparing exisitng case, best case and recommended case temperatures at 3 pm

The graph illustrates the temperature at 3 pm at different heights comparing the existing case, recommended case, and the best case. The x-axis represents the height in meters, and the yaxis represents the temperature in degrees Celsius. An average of .1.41C at ground level and 1.52C at human height level is observed. Even though there is almost 1C difference between best case scenario with granite pavement and Sandstone pavement in recommended case, as the height increases, this difference diminishes.

The percentage reduction of Air temperature at ground level for recommended case is 3.59% .

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8.1 Cost- Benefit

Scenario

Model specifications

Cost - Benefit

Urban

4m X 4m green patches

High capital cost

Vegetation

7m tall trees

Neutral operational costs

4m X 4m green patches

Shading/Biodiversity benefit

15m tall trees

Socio-cultural benefit

Sunshade sails at 2m

Neutral capital costs

Urban shading

Sunshade sails at 4m Urban Pavers

Sandstone pavement Granite pavement

Best

case

High operational costs High capital costs No operational costs

Green patches, 7m and 15m tall trees

High capital costs

Vegetation,

2m and 4m sunshade sails

Neutral operational costs

shading

Granite pavers

Shading and Biodiversity

Recommend

Green patches, 7m and 15m tall trees

Neutral capital costs

case

2m and 4m sunshade sails

Neutral operational costs

Sandstone pavers

Cultural identity

and

pavement

Biodiversity Year-around strategy Table 17- Cost-benefit analysis for proposed strategies

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9. Conclusion In conclusion, this study aimed to explore and evaluate various heat mitigation strategies for Ajmal Khan Road, a bustling commercial street in Karol Bagh, Delhi, by using ENVI-met simulations.

Several lessons have emerged through the process, highlighting both the potential and limitations of different urban interventions in this specific context. A combination of theoretical findings and practical constraints has led to a nuanced understanding of which strategies are most effective and realistic for this environment. 

The simulations showed that heat mitigation strategies must be read in conjunction with each other. Temperature reductions alone do not provide a complete picture. Parameters like relative humidity, wind speed, and surface temperatures also have a significant role in shaping the effectiveness of a strategy. For example, in scenarios where relative humidity was high, granite pavers underperformed despite their superior heat-reflecting properties.

Sunshade sails, too, demonstrated that while they reduce direct solar radiation, their effectiveness was limited in areas where wind circulation was poor, especially at lower heights. Therefore, a more holistic approach to urban heat management is crucial.



The best-case simulation, which combined urban vegetation, sunshades, and granite pavement, theoretically showed the most significant temperature reduction, with ground-level temperatures decreasing by up to 4.9%. However, when considering the specific context of Ajmal Khan Road, this strategy became less viable. Granite pavement, while effective reducing surface temperatures by up to 7.9%, faced practical challenges. Its high cost, coupled with cultural and aesthetic disconnects with the local street market, made it less suitable for implementation. Instead, sandstone pavement, despite being less effective in temperature reduction, was more aligned with local market aesthetics, cost constraints, and ease of maintenance. This highlights the importance of tailoring urban interventions to fit the specific socio-cultural and economic context, rather than relying solely on theoretical efficacy.



One of the key findings was the varying degrees of reflection and absorption among different materials. Light-colored materials like granite performed better in terms of reflecting solar radiation and reducing surface heat build-up, whereas darker materials like asphalt exacerbated heat retention. In the monsoon season, however, the efficacy of granite diminished due to its poor performance in high-humidity environments, while sandstone, being more porous, offered a more balanced approach by retaining less heat and providing

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slight cooling through moisture retention. This finding underscores the need for dynamic, seasonally adaptable strategies, as material performance can vary significantly across different climatic conditions. 

Urban vegetation is one of the most consistently effective strategies. Trees, particularly when planted at heights of 7 to 15 meters, significantly improved thermal comfort by reducing air temperatures by 1.7% and surface temperatures by 4.5%. Moreover, the cooling effect of trees extended beyond just the ground level, affecting the overall microclimate at higher altitudes, unlike sunshades and pavement materials, which had more localized impacts. This reinforces the critical role that vegetation plays in urban heat mitigation and highlights the need for long-term investments in green infrastructure.



Sunshade sails, while effective in theory, presented practical complications. At heights of 4 meters, sunshades performed relatively well, reducing surface temperatures by up to 4.9%.

However, at lower heights, such as 2 meters, their effectiveness was hindered by poor air circulation, trapping heat and preventing proper cooling. Furthermore, the placement and height of sunshades need to be carefully considered to avoid interference with wind flow and other urban elements like streetlights and overhead wires. Despite their advantages in reducing direct solar exposure, the operational costs of maintaining and replacing sunshades, particularly during heavy rains and winds in the monsoon season, present significant challenges. Sunshades, therefore, are a viable strategy but require strategic planning in terms of placement, height, and ongoing maintenance.



The lessons learned from this study suggest that the most effective heat mitigation strategy for Ajmal Khan Road is a balanced, context-sensitive approach. Urban vegetation offers the highest long-term benefits, both in terms of reducing temperatures and improving overall street aesthetics and air quality. However, the combination of sunshades and appropriate paving materials also plays a vital role in enhancing thermal comfort during the hottest hours of the day. The recommended scenario, which involves a mix of sandstone paving, retractable sunshades at 4-meter heights, and strategically placed trees, strikes a balance between theoretical temperature reduction by 1.4C.

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This study has shown that urban heat mitigation strategies cannot be one-size-fits-all solutions; they must be adapted to fit the specific challenges and opportunities presented by each urban environment, hence answering the research question.

By adapting the framework and lessons learned in this study, city planners in similar climates could devise context-specific solutions that align with local socio-economic conditions, cultural preferences, and environmental needs. Furthermore, at a global level, this model could contribute to larger-scale strategies for controlling urban temperatures, potentially helping to mitigate the overall effects of global warming by reducing heat build-up in urban areas, thus making cities more resilient in the face of rising temperatures worldwide.

This approach highlights the potential for scalable, targeted urban interventions to help reduce global urban temperatures and alleviate the impacts of climate change.

9.1 Limitations Climate data availability: For more accurate simulations, weather data of the neighbourhood or even street would have been helpful. The limited weather station locations and lack of technological advancements restricts data collection and precision in analysis for many developing cities.

ENVI-met Software: Running simulations in ENVI-met software was a computationally intensive and time-consuming process, often requiring several hours or even days to complete.

9.2 Opportunities Scalability: Successful implementation in Karol Bagh could set a precedent for other market streets in Delhi and other tropical cities. The principles of reflective paving, adaptive shading, and green infrastructure can be applied in various urban contexts.

Integration with Urban Policy: Findings from this study can inform urban heat mitigation policies at the municipal level, contributing to sustainable urban planning in Delhi.

Sustainability Goals: The use of natural cooling mechanisms like vegetation aligns with broader sustainability goals such as reducing urban heat islands and promoting environmentally friendly urban spaces.

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9.3 Next Steps 1. Field Testing: The proposed strategies need to be tested in real-world conditions at Karol Bagh market to assess their efficacy in reducing heat exposure for street vendors. A pilot project involving a section of the market can serve as a testbed for the proposed solutions.

2. Further Analysis Using ENVI-Met: Detailed simulations using ENVI-Met software should be conducted to analyse the thermal comfort of vendors and pedestrians under different configurations of pavement materials, shading, and vegetation throughout the year. This would provide precise data on temperature reduction and humidity effects.

3. Community Involvement: Engage with the local community, including vendors and shop owners, to understand their needs and gain feedback on the proposed solutions. This would ensure that any changes made to the market infrastructure align with the daily practices of those who work and shop there.

4. Other parameters: This study is limited to strategies that are independent of buildings. By implementing strategies such as green walls and roofs, reflective building fabric and surfaces, the temperature reduction can be multiplied. These strategies all add to reduction in energy usage as well.

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10.

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