Towards Liveable Streets Urban Canyon Microclimate: An Empirical Study of Colombo LIBRARY UNIVERSITY OF MORATUWA, SRI LANKA MORATUWA

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1 Towards Liveable Streets Urban Canyon Microclimate: An Empirical Study of Colombo LIBRARY UNIVERSITY OF MORATUWA, SRI LANKA MORATUWA A Dissertation Submitted to the Department of Architecture of the University of Moratuwa in partial fulfilment of the Requirements for the degree of Master of Science In Architecture 85445,, «... V, University of Moratuwa Silva G.R.H January J ^ \,v. :><m _ II

2 DECLARATION I declare that this dissertation represents my own work, expect where due acknowledgement is made, and that it has not been previously included in a thesis, dissertation or report submitted to this University or to any other institution for a degree, diploma or other qualification. Signed: (G.R.h"Sifva) ii

3 > ACKNOWLEDGEMENTS This study with many complexities and difficulties completed due to the assistance, guidance and encouragement given by all of the following persons, to whom I wish to extend my heart full gratitude. Archt. Vidura Sri Nammuni Head, Department of Architecture University Moratuwa, for his assistance in this study. of My Coordinator Archt. Prasanna Kulathilake, Senior lecturer, Coordinator M.Sc. Dissertations, Department of Architecture for comments and criticism which encouraged me to do this study. I am deeply indebted to my tutor Archt Dr. Indrika Rajapaksa Lecturer Department of Architecture for her guidance, valuable comments and unreserved help given to me for the completion of this task. Archt. Dr. Rohinton Emmanuel, Senior lecturer, Department of Architecture, for his guidance, valuable comments and unreserved help given to me. The staff of Department of Architecture. ^ Mr. Chathura, Technical officer, for the given help on arranging the instruments. Librarian and Staff, University of Moratuwa Library and University of Peradeniya Library, for the given help. Mr.Padmasiri and his staff for their kind guidance and help on obtaining Data from the Metrological Department, Colombo. O.I.C. 's Administration in Dehiwala, Wellawatte, Bambalapitiya, Kollupitiya and Pettah Police Stations for their assistance for possible arrangements in having the Defense clearance to carryout the Field study survey and photograph the high security zones within Colombo. I'm also grateful to my seniors, Miss. Sathya Sajeewa and Miss. Nirosha Loyed and 4 Mr Narain Perera for the assistance provided. I offer my heartfelt thanks to my dearest friends Panawala.Bashwara, Champika, and my batch mates for their valuable support rendered in completion of this task. Last but not least I express my deepest gratitude to my dearest parents, and my Sister for their support and for always being there to take my troubles in a most loving way. iii

4 Towards Liveable Streets Urban Canyon Microclimate: An Empirical Study of Colombo CONTENTS Page No. Declaration Acknowledgements Table of Contents List of Figures Abstract i ii iv vii xii INTRODUCTION A. Significance 1 B. Objectives 4 C. Hypothesis 5 D. Method of Study 6 E. Scope and Limitations 7 CHAPTER ONE: URBAN DESIGN AND ITS EFFECTS ON URBAN CLIMATE (LITERATURE REVIEW) Introduction to the Chapter Urban Climatology Urban Temperature: The Heat Island Phenomenon Urban Wind Field Radiation and Sunshine Urban Design Effects on Thermal Behaviour of Urban City The location of a town within a Region Size of cities Density of the built- up area Land coverage Overall spatial pattern of the urban heat islands in equatorial regions Characteristics of urban heat islands in equatorial regions 21 Concluding Remarks 23 iv

5 CHAPTER TWO: LIVEABLE STREET: ESSENTIAL SPACE OF URBAN DESIGN IN EQUATORIAL CLIMATES (UTERA TURE REVIEW) Introduction to the Chapter Public Realm as "the" Essential Space Street as an Architectural Entity Sense of enclosure Sense of direction Street as the Key Public Domain Outdoor Activities Life between Buildings Thermal Comfort: The Key Facilitator of Physical Comfort Thermal Comfort-Theoretical Basis Architecture and Thermal Comfort Thermal Comfort in equatorial urban outdoors Location considerations within equatorial regions Layout of the streets networks , Urban density and building heights in equatorial regions 40 Concluding Remarks 42 CHAPTER THREE: URBAN CANYON GEOMETRY (Literature Review) Introduction to the Chapter Urban Design Effects on Thermal Behaviour of Urban Canyon Aspect Ratio Sky View Factor (SVF) Radiation Urban density and the characteristics of urban wind field Perpendicular wind Parallel wind Oblique wind Canyon geometry impacts on thermal comfort in equatorial regions 56 Concluding Remarks 61

6 CHAPTER FOUR: URBANIZATION TRENDS OF COLOMBO AND ITS EFFECTS ON URBAN CLIMATE Introduction to the Chapter Equatorial Climates Climatic Characteristics of Sri Lanka Climate Change Predictions in Sri Lanka Colombo: Urbanization and Heat Island Urbanization the city Of Colombo Historical Trends in urban climate in the Colombo 71 Metropolitan region Colombo city as an Urban Heat Island Problems related to Colombo City Microclimate 75 Concluding Remarks 77 CHAPTER FIVE: CASE STUDIES Introduction to the Chapter Approach to the Research Site Selection Development of a typology On-site measurement and its variations in relation to an independent source Site traverse Analysis techniques Canyons Shading Patterns North- South Oriented Urban Canyon 86 CHAPTER SIX: ANALYSIS AND URBAN DESIGN IMPLICATIONS 6.1 Analysis Urban Design Implications The East-West Street The North-South Street

7 6.3 Development of a "Human Zone" North - South Oriented Urban Canyon East- West Oriented Urban Canyon 116 CONCLUSION 119 BIBLIOGRAPHY 124 Appendices vii

8 LIST OF FIGURES Fig: No Page 1.1 Sketch of a Urban Heat Island Profile Urban Canopy and Boundary Layer over cities Schematic illustration of the effect of topography on local wind 14 exposures 1.4 Measured air temperatures at UCLA during 57 days spread over a 15 year in sites with different ground cover 1.5 Measured surface temperatures of the sites Crystal down town centers in San Francisco many smaller cities especially in the developing world mill retain 20 their spontaneous layout in human scale 1.8 Metilli in the Algerian Sahara home of the Chamba Sense of enclose - Galle Road, Bambalapiatya Sense of Direction Streets - The Public Realm Necessary activities - under all conditions Optional activities - only under favorable exterior conditions Social Activities on Streets Graphic representation of the relationship between the quality of 30 outdoor spaces and the rate of occurrence of outdoor activities 2.8 Mind Map - Relationship between Vitruvian Tri-parlrte of climate balance Interlocking fields of environment Bio climatic chart Seven point Numerical Scale Boundaries of outdoor temperature and humidity Climatic boundaries in terms of the outdoor maximum daily 37 temperature 3.1 schematic distribution of the impinging solar radiation a) an open flat county 44 b) a built-up area with H / W ratio of about 1 44 c) a high-density urban area with H / W ratio of about In urban areas -the fraction of sky visible SVF=1 in an open site or on a rooftop 47 viii

9 3.4 Height, Width and Length of a canyon Wind direction perpendicular to the Long Axis The flow pattern associated with air flow over building arrays of 51 increasing 3.7 Threshold lines dividing flow into three regimes as functions of the 52 building (L/H) and canyon (H/W) geometry 3.8 Single vortex pattern Two vortices regime in deep canyons Wind flow direction parallel to the Long Axis wind speed near ground level in front of a high-rise building is 58 increased helping in diluting street-level air pollutants 3.12 Graphical Illustration of the changes in the vertical wind velocity 60 profile over urban, suburban and open rural areas 3.13 air temperature measurement, owing two days in three streets of 60 very different width ranging from a wide Avenue to a very narrow alley in Seville, Spain 4.1 climatic regions of the World Important sun positions on Sri Lanka Future expecting rain fall values- Sri Lanka City of Colombo Population Densities -Colombo public outdoor relation space proposals Location map of weather stations in the Colombo metro region Thirty-year diurnal variations in temperature during the hottest 72 month in CMR 4.9 a) Historical trends in Heat Index - Colombo Weather station 73 b) Historical trends in Heat Index - Rathmalana Weather station 73 c) Historical trends in Heat Index - Katunayake Weather station Givoni's Bioclimatic recommendations based on Colombo's typical 75 climate Colombo City - urban structure Colombo Map - The research area Classification of basic canyons in relation to canyon height No of floors and approximate height of basic Canyons survey of Canyons - Colombo Hobo-HT 83 ix

10 5.6 a) SVF- Symmetrical Canyons 85 b) SVF- Asymmetrical Canyons The Eastern Pedestrian Walkway shallow canyon Typical Canyon - Galle Road Sunshine Hours above Eastern Pedestrian Walkway of the 87 Canyon - Galle Road 5.11 Sunshine Hours above Western Pedestrian Walkway of the 88 Canyon 5.12 Shadow Pattern comparison of Shallow, Intermediate and Deep 90 Urban Canyons on Galle Road, Colombo 5.13 Categorization of canyons and availability Percentage width of shadow in relation to the Canyon width, on 92 Shallow Canyon of Galle am during the Year 5.15 Percentage width of shadow in relation to the Canyon width, on 93 Shallow Canyon of Galle pm during the year 6.1 Correcting the measured data according to the trend pattern of 95 that particular period 6.2 Research Area 95 THI variation on the North-South Oriented Street- Galle Road Overall THI variation - Galle Road THI variation on the East-West Oriented Street; Lotus Road and 97 Olcott Mawatha 6.6 Overall THI variation -Lotus Road Overall THI variation - Olcott Mawatha Analysis of Selected Typologies 99 - (a be Arcades.York Street, Colombo Mulberry Street, with Narrow sidewalks and slow pedestrian traffic 106 Little Italy Narrower, tree-shaded streets Buildings that present a friendly face to the street have porches 107 and trees 6.13 Shaded by means of the canyon height 108 Broad Street, Philadelphia 6.14 Broad Street, Philadelphia 109 X

11 6.15 Street section-hawkers pavement shelter Section through a riparian arterial Along a riparian greenway, an artificial stream provides habitat 110 and biofiftration of surfacewater Human Zone 1.5m in width, 2.00m high Space on walkway 111 adjoined to the built mass 6.19 Horizontal shading device and Shadow Angle ( B) Vertical shading device and Shadow Angle (<t>) Plan ; North -south Oriented Canyon Typical section; North- south oriented Canyon Plan; East-West Oriented Canyon 116 % Monro? xi

12 Abstract Urban Design; Designing an Urban setting, it self can perceive as a single architectural process, not only an individual building, but also the way buildings are related each other and its three-dimensional composition represents the total image of the city. Performances of these solid-void compositions directly effected to thermal behaviour of the city. The metropolization phenomenon at Colombo has provoked deep changes in the field of "Urban design". As well, as changes in thermal comfort levels and the energy balance, leading to an altered atmosphere of the urban area, In Colombo, higher relative humidity values and moderation in wind speed, the daily (diurnal) variation in temperature and diminishing diurnal temperature variation would indicate a growing UHI problem. The phenomena of Urban Heat Island can create unpleasant microclimatic conditions at the pedestrian level. Pedestrian walkways are the key pubic domain of Equatorial towns and cities, where the greatest amount of human contact and interaction taken place. Shading can create a comfortable level, avoids the direct solar radiation. Vegetation in particular tall trees can create a cooling effect, lower temperature and increase relative humidity. The aim of this study is to investigate the effect of Orientation, built mass, tall trees with a wide foliage canopy and water bodies, on the climatic parameters, at the pedestrian level in street canyons, Colombo metropolitan. The research was conducted in either-side pedestrian walkways of two major public realms selected based on its Orientation. Each street canyon consisted with areas of deep, shallow and intermediate canyons, tall dense trees planted, street canyon relatively lacking in tall trees, directly effected water bodies etc. One pair of walkways was located parallel to and, the other perpendicular to, the coastline. Data collected in two days of December 2003: Temperature and relative humidity, by a HOBO-HT data logger, in a well cross-ventilated radiation shield at seven feet height on each pavement, Traverse walking along canyon, by which temperature and relative humidity were, measured using the mobile data logger at midday and night, in Dec 18 th and 22 nd. The results show that during the day hours the temperature values in the canyons with vegetation were up to 2 THI values lower than those measured in the canyons without trees and it was up to 4 THI values lower in Gall face Green, where directly affected by the Ocean. Wind speed in the canyons placed perpendicular to the coastline, was generally higher than in the canyons located parallel to the coastline and blocked by rows of building from the sea breeze, which is a characteristic of Sri Lankan western shoreline. But the effect of vortex phenomena caused by perpendicular winds, can clearly experienced in N-S oriented deep canyons, Wind speed in canyons without trees was generally higher that in canyons with threes due to the windbreak and friction effects of the trees in the latter. The existence of shading devices above the pavements and tall dense trees in an urban environment could result in two opposite climatic effects. Shading devices moderate the air temperature and surface temperatures, preventing the direct solar radiation. In addition, trees act as moderators in both temperature and relative humidity levels towards comfortable levels. This research shows imperative need of interferences, of climatized architectural imlpiceations in the case of street canyons and adjoined pedestrian walkways at the Colombo Metropolitan. xii

13 INTRODUCTION

14 Towards Liveable Streets: Urban Canyon Microclimate; An Empirical Study of Colombo Introduction INTRODUCTION Architecture is primarily a spatial experience and it is the "unavoidable observation''. Whether it is Day or Night, through out the day beholder is exposed to it. Architecture corroborate his life, take care his being. It directly addresses Physical as well as psychological comfort of its beholder. City and Urban Design, consists of, physical forms, which can conveniently be classified in to five elements: paths, edges, districts, nodes and landmarks. It can be also defined as a place where, harmonising the balance between public domain and private domain, where the public realm, the continuity of public spaces is become crucial. City, Urban setting it serf can perceive as a single architectural entity, not only an individual building, but the way buildings are related each other and formed the total image of the city. The way people experience the city, the urban setting, and spatial relationships are been concretised a city to be perceived as a tangible architectural entity. "Architecture and urban design should express the positive values of a society and reflect the sum of its social and economic achievement. Architects should act as coordinators on behalf of the public interest and be the advocates for a harmonious, human environment" (Hosken 1973) So, as the work of architecture contributes, City also should address to the physical and psychological need of it's' inhabitants. If "Psychological Comfort" is the ultimate determination to succeed in the work of architecture, "Physical Comfort" could be sighted as the provider of that goal. Physical Comfort most of the time follows "Thermal Comfort". It cannot be separated. The appropriate level of "Thermal Comfort" is the essential and the major facilitator of that achievement. So "Thermal Comfort" is the key prerequisite to achieving "Psychological comfort". The achieving of psychological comfort of the spatiality of the city, assert to be as reaching to appropriate thermal comfort level in both public and private realm and in elements ; paths, edges, districts, nodes and landmarks as a unique spatial entity. In the perceiving of the thermal behaviour of a city it serf, could be identified as a separate pattern in the composition of the classified elements of formatting a city; a clear relationship between physical spatial arrangement and thermal behaviour of the city can be identified.

15 Towards Liveable Streets: Urban Canyon Microclimate; An Empirical Study of Colombo Introduction Streets and Paths became the heart of physical spatial arrangement of the city and of the civic life, Specially "Streets'' in Sri Lankan context. The public streets, of a country such as Sri Lanka is mostly associated with the buildings that planted along the street and its own generated activity pattern. It will incorporate all the buildings, which will open out to the street and its related activities or the usage of the space as a place. Buildings along streets form urban street "canyons" that cause the urban surface to take on a distinctly three-dimensional character in the form of both physically as well as thermally. According to Oke (1987) he states Urban Canyon, as, "An Urban canyon is comprised of the walls and ground (road, garden, etc.)between two adjacent buildings as well as the canyon-air volume, which has three sides with active surfaces (walls and ground) are three open sides (ends and top)" This three dimensional form affects the absorption of solar radiation, surface temperature, evaporation rates, storage of heat and the turbulence and wind climates of cities and can drastically alter the conditions of the near-surface atmosphere. The Urban Canyon effect, the phenomenon is one of the major factors which push the Cities to formulate their own microclimates. Urban areas are both affected by weather and climate, and exert an influence on the local scale weather and climate. The climate in and around cities and other built up areas is altered in part due to modifications humans make to the surface of the Earth during urbanization. The Ground surfaces are typically rougher and often drier in cities, as naturally vegetated surfaces are replaced by buildings and paved streets. People choose settings with characteristics, which they highly expected is psychologically comfortable living environments and avoid environments which they feel negatively, when preferred environments cannot be selected. They push in to adaptation or to discouraging to participate in certain activities. Therefore the understanding of urban street phenomenon is critical. It can be said, canyon microclimate of urban streets defines the physical comfort of the user and it's creation of psychological comfort of him, which generates social functions possible. Although "life" in the equatorial tropics is largely an outdoor phenomenon, modem urban development has been failed to facilitate such living in a climatically pleasant manner.

16 Towards Liveable Streets: Urban Canyon Microclimate; An Empirical Study of Colombo Introduction The reflectivity of the materials used in the front facade of the buildings causes the major effects on urban canyon geometry, on thermal comfort of the street life and ultimately effected on psychological comfort of inhabitants of the city. So, the "Urban Canyon" becomes the very important "three dimensional physical form", in the provision of determining the microclimate, thermal comfort and psychological comfort of the city and its inhabitants. The approach then should be an attempt to identify the existing situation of the thermal behaviour in urban canyons in Colombo and make (or modify the existing situation) equatorial urban outdoors thermally comfortable and liveable. A. Significance Street; Path is one of the most important component in analysis of spatial elements of a city, in the experience physical perception. It is the linking and binding space, also a link between one space and another. The public realm of a city depicts the continuity of these public spaces, and it is the most important part of Equatorial towns and cities, where the greatest amount of human contact and interaction taken place. It is the key public domain in equatorial tropics, where people gather. "Streets and their sidewalks, the main public places of a city are its most vital organs. Think of a city and what comes to mind? It's streets. If a city's street look interesting, the city looks interesting; if they look dull, the city looks dull" (Jane Jacobs 1965:39) Public realm of a place is a contribution of Architecture. Urban Design and the Human Being. So the liveness of Public Street becomes an essential task in urban designing. Present day, in urban designing, the considerations relating to people and the way in which they interact have tended to be neglected, especially in an urban street. Street as a public space, participates in the construction of the individuals as well as the symbolic experience of society in its diversity. It is a common question asked by many is what the relationship between thermal comfort, and urban design. An urban designer produces design and set of guidelines for future development based on density, massing, materials, transport and etc. These elements ultimately consume energy in various forms to carry out their function. If each and every single designer produce a design without considering the natural forces,not only the consumption of energy and recourses

17 Towards Liveable Streets: Urban Canyon Microclimate; An Empirical Study of Colombo Introduction will be utterly inefficient.but also environmental degradation will be very high due to the emission of pollution and wastes. This phenomenon that causes by each building ended with lot of environmental problems in the end in macro situation; Urban Heat Island In Sri Lanka, Colombo as the major commercial and administrative centre, the built to unbuilt ratio of the city fabric is going to be very low in near future, means that increases the surfaces area of heat capturing and reflecting within the city. The totally glazed facade results the air-conditioning of the building. Although air-conditioned interior of these glass capsules is comfortable to carry out whatever the work in efficiently, it releases lot of heat to the exterior of it's own generated, through AC plants and as radiant heat which reflected by the tinted facades. All this heat releases in to the public streets without a control, admit will directly effected to the city life with combination of thermal effects occurs by width of the Road, building height, wind pattern and building materials used in the street facades. This effect becomes extremely worse in a deep Urban Canyon. The effects of this phenomenon is directly pushing the liveable public spaces, in to dead spaces, and ultimately towards a dead city. B. Objectives The intention of the study is to identify the relationship between Street Form and thermal behaviour of urban canyon microclimate of Colombo which based on case study and observation. Also to understand the three-dimensional patterns of public space which directly affects the thermal behaviour of the street enclosure. Study is attempted to guide architectural responsiveness to the environment with reference to a basis, which leads to create a liveable city, through a liveable Urban Canyon. Finally the analysis will proceed into the potentials to rejuvenate life in streets. Therefore the study aims to focus on: o o Historical development of the physical structure as well as the activity pattern which had been developed over a period of time and causes of selected Urban Canyons, To study and analyze activity patterns of selected existing urban canyons and thermal behaviour of the street enclosure, it will try to introduce a basis which includes patterns to create a liveable city. 4

18 Towards Liveable Streets: Urban Canyon Microclimate; An Empirical Study of Colombo Introduction o For the analysis purpose of the causes which govern the life patterns of the public places especially in urban canyon, it will introduce qualities of a responsiveness of the built environment to create a liveable place. o Using the fundamental basis of the public realm of a place is evaluated and this proceeds into understand the relationship between the analysis and rejuvenating street life, and the quality of the life in a liveable city. o On-site data collection and subsequent thermal evaluation / comparison of the spaces within the street, which allow for the selection of focused urban spatial patterns. The conclusion will provide the analysis and enabling potentials to use the urban street as the principle mode of public realm in the context of Sri Lanka by achieving a physically and psychologically comfortable public living standards towards "liveable streets", through a higher level of thermal comfort. Man- environment interaction in an urban street, how it's really experienced and comprehended, and the effects of such values and the accessibility of the street space is also explored. C. Hypothesis o o o o Dense areas of vegetation and water bodies influence climatic parameters of surrounding areas, Shading or shaded areas of the urban canyons have a distinct positive bearing on the thermal comfort of its beholder, The orientation, sky view factor and the ratio of building height to the width of the canyon considered can be consciously modified in order to achieve the shade. Increased height to width ratio of the built mass increases the level of thermal comfort. 5

19 Towards Liveable Streets: Urban Canyon Microclimate; An Empirical Study of Colombo Introduction D. Method of the Study Method of study is a Case Study based approach. The study evaluates the effect of the building surfaces, built mass on shading and thereby the thermal comfort of urban public space in an empirical manner. The case studies were selected by an investigation and considering following parameters of the urban structure in Colombo o Orientation of Canyon, Symmetric / Asymmetric Canyon, width to Height ratio o Canyons with special Features: Water Bodies / Vegetation o Sky View Factor o Air Flow Characteristics: Perpendicular wind / Parallel Wind / Oblique Wind & Roof Type (Flat / Pitched / Gable) o Zoning of Activities: Commercial / Residential / Mixed Development o Vehicular Movement: Heavy / Intermediate / Low Traffic Flow o Boundary Layer Characteristics Materials Used in the Street envelope o Activity Pattern: which is functioning in the Urban Canyon o Shadow-Umbrella Phenomenon: Shaded areas caused by buildings and exposed time duration, Existing situation and importance and the value remaining regarding the form of the street, According to their particular location, and the permeability of the place. A typology of urban canyon developed on the basis of above parameters. Derive a structure to select the case studies based on the criticality of thermal behaviour which is directly address the psychological and physical comfort of the beholder and their activities happening within the "street canyon". In the selected streets in urban canyons in the settings of which encompasses varying typologies of public space relative to the main focus of "urban canyon", and is studied for its bio climatic patterns, onsite measurements on temperature (dry bulb air temperature.wind speed and direction, Humidity, Physical form mapping, behaviour study, photographic survey, graphical survey and observation by the researcher, is also carried out specially considering three-dimensional form, activity pattern, and permeability of the place. On-site data collection and subsequent thermal evaluation/compression of the spaces within the selected urban canyons, which allow for the selection of focused urban spatial patterns. The present thermal behaviour of the selected sections of the street and envisioned modifications, are to be proposing in generating variations of THI index in the form of urban design implications. 6

20 Towards Liveable Streets: Urban Canyon Microclimate; An Empirical Study of Colombo Introduction E. Scope and Limitations Public realm of a city can be a collection of spaces as streets, squares, boulevards, gardens etc. but the study here mainly focused on to the urban streets, the Urban Canyon. There are a range of factors to consider in evaluating the Thermal Comfort values of a given situation, which is directly influenced the behavioural pattern; such as street patterns, spatial pattern of city function by it self, and way each of these are relate each other are also to be consider. But those aspects will not be considered is the study. It is beyond the scope of study. Aspect here it would examine the human behaviour and directly related comfortable factors in-depth, in relation to the urban street-canyon environment and the way people behave within that architectural entity. Yet it explored into, the physical form, and the formal design aspects of a place. Therefore the study stresses on the behaviour of thermal effect on an Urban Canyon and its effects on the liveable street life, related activity pattern (i.e.; in terms of community life and people). A data range conveying a longer time period about several years, within an year, within a day both in day and night, rainy seasons, windy seasons should consider in order to derive a concretise decisions and would result in the formation of more accurate trends in patterns considered. The limitation of the data range being restricted to a single day, both day and night of the years. 7