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THE EFFECT OF RAPID URBANIZATION ON THE PHYSICAL MODIFICATION OF URBAN AREA

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Today rapid urbanization is a major challenge for many cities. In 2007 urban population started to exceed the rural population. Increasingly, scholars and governments discuss the effects of this trend on future development of cities. It is obvious that any kind of urban development should be controlled and regulated, otherwise the outcome could lead to a chaotic and unsustainable development. Besides, it may result in environmental problems like air pollution, heat islands, urban climate and etc. Unfortunately, this kind of physical modification practically have not been considered by the planners and designers. The current study is grounded on recent literature review and tries to concentrate on this problem mainly from the development and construction performance perspective. Moreover, the current study attempts to classify the effective variables under the urban form, urban geometry, and urban population.
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S.ARCH-2018 05.183.1
THE EFFECT OF RAPID URBANIZATION ON THE PHYSICAL
MODIFICATION OF URBAN AREA
Kamyar FULADLU*a,b, Müge RİZAa, Mustafa İLKANb
Eastern Mediterranean University
a. Faculty of Architecture, Department of Architecture, Famagusta, Northern Cyprus,
Postcode: 99628
b. School of Computing and Technology, Department of Construction Technology,
Famagusta, Northern Cyprus, Postcode: 99628
e-mail: kamyar_fuladlu@yahoo.com
Abstract
Today rapid urbanization is a major challenge for many cities. In 2007 urban population
started to exceed the rural population. Increasingly, scholars and governments discuss the
effects of this trend on future development of cities. It is obvious that any kind of urban
development should be controlled and regulated, otherwise the outcome could lead to a
chaotic and unsustainable development. Besides, it may result in environmental problems
like air pollution, heat islands, urban climate and etc. Unfortunately, this kind of physical
modification practically have not been considered by the planners and designers.
The current study is grounded on recent literature review and tries to concentrate on this
problem mainly from the development and construction performance perspective.
Moreover, the current study attempts to classify the effective variables under the urban
form, urban geometry, and urban population.
Keywords
Urban Form; Urban Material; Urban Population; Sustainability; City Planning
1 Introduction
The world urban population for the first time in 2007 exceeds the rural population. The
United Nations (2015) based on the current trend believe that by 2050 about two third of
the world population will live in the urban area [1]. Besides anything else, the economic
growth itself contributes to the increase of the urban population and associated with the
urban development too. It is obvious that any kind of urban development should be
controlled otherwise the outcome could lead towards a chaotic and also unsustainable
development.
Unfortunately, especially in developing countries due to the rapid population growth, cities
developed without a planned and regulated development policy. Obviously, this sort of
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developments has several severe negative effects, which somehow are solved by
engineering, medicine, agriculture and etc. However, the physical impacts like urban climate,
air pollution, Urban Heat Island (UHI) etc. practically have not been considered by planners
especially at microscale [2].
Fundamentally, dozens of variables include geographical location, regional meteorology,
urban morphology, surface materials, vegetation/water bodies, human activity, and etc. are
responsible for the physical implication in the urban area [3, 4]. The current study based on
contemporary literature tries to figure out the effect of these variables on the physicals
modification of the urban area. Apart from that, unlike any other study, in this study, the
main concern is microclimate and neighborhood scale.
This study aims to explore the role of urban development with a focus on the microclimate
and the neighborhood level to the physical modification of the urban area. Therefore, firstly
recent transformation of the urban area considering the role of the modern built
environment is discussed. Secondly, dimensions for the physical modification of the urban
area are discussed. Afterward, the association of these dimensions are represented by the
physical modification of the urban area.
2 The urban development and role of the built environment
In the current era, the increase of population and demand for housing etc. rapidly increase
the construction of buildings inside the cities and spreading outwards the boundaries of
cities. As a consequence, the hard surface of construction materials such as concrete, street
pavement, roof material and etc. are expanding and replacing natural surfaces and green
areas.
However, the transformation of the natural surface into construction platforms such as
modern built environment has several negative impacts on the existing thermal balance.
When vegetation and green surface is minimized and large surfaces are covered by rough
and less permeable surfaces, it contributes to the decline of evaporation and increases the
heat storage as the construction surfaces e.g. are not dense as the natural surfaces [5].
Moreover, the notable amount of solar radiation is stored by construction material with
rough surface, dark color and less albedo [4, 6, 7, 5, 8].
This situation directly influences the overall air ambient temperature of the urban area. As a
result, the urban area becomes warmer in comparison to the surrounding area. At the
moment, this phenomenon is well-accepted and known as Urban Heat Island (UHI) effect
(Figure 1). The UHI clearly defined as a temperature difference between the urban and rural
( ) areas [2, 6, 9].
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Figure 1. The effect of Urban Heat Island (UHI)
As stated before, the wide range of the natural and the man-made factors include seasons,
cloud cover, wind speed, sunlight, urban canyon geometry, surface material, anthropogenic
heat, and etc. are responsible for emerging of this phenomenon.
Up to now, countless studies consider this issue from different perspective, for instance
Dimoudi & Nikolopoulou (2003) and Leuzinger, Vogt & Körner (2010) consider the
vegetation impacts on urban environment, Taha (1997) consider the material,
evapotranspiration and anthropogenic heat, Stone Jr. & Rodgers (2001) study on form of city
and urban design and Jamei, Rajagopalan, Seyedmahmoudian, & Jamei (2016) review the
impact of urban geometry on outdoor thermal. Unlike all of them, the current study firstly
grounded on the primary physical properties Evaporation, Heat Storage, Net Radiation,
Convection and Anthropogenic Heat which are represented by Gartland (2008). Secondly,
the main concern for this study is the microclimate and the neighbourhood level.
According to the Gartland (2008), reduced evaporation and convection from one side,
increased heat storage, net radiation, and anthropogenic heat from another side
tremendously influences the physical modification of the urban area [10].
Figure 2. The energy balance and the physical modification of the urban area
The above given dimensions (Figure 2) together represent the energy balance equation Eq.
(1) too. The terms of energy balance in this topic represents the transformation of energy on
the earth. In other words, based on the first law of thermodynamics, the energy never
Source: Author
Source: http://coolparramatta.com.au/about_us
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created nor destroyed. While, it can be transferred from one location to another or it can be
converted from one form to another form of energy.
Net Radiation + Anthropogenic Heat = Heat Storage + Convection + Evaporation (1)
To have a better insight into the energy balance and association of it with physical
modification of the urban area, each of its dimensions are explained below.
2.1 Evaporation
The evaporation process is responsible for transforming a liquid into a gas form. In the
atmosphere the available water on the wet surface, runoff, moist soil, and etc. by sun heat is
converted into the vapor. Within this process, the sun’s energy from the atmosphere
transmitted to the earth surface. Whenever it collides to the wet surface, it turns into the
vapor. The evaporation increases when the moisture and the fast wind available. The
evaporation intensified in the warm-dry climate condition. Loss of evaporation results in
increase in the heat storage capacity during the day, and then the stored heat is released at
night. Therefore, the loss of evaporation can turn the construction platform into a place for
the energy store [5, 10].
2.2 Heat Storage
The ability of the substance to absorb an amount of heat to increase its thermal
temperature, known as the heat capacity. Therefore, a material with a high amount of heat
capacity can store more amount of heat. Of course, the role of thermal conductivity is also
important to measure the physical ability of the substance to transfer the heat by its
molecular motion [11].
The heat storage with moisture has an inverse relationship too. In fact, the construction
material which is minimized on the wet surface has negatively effect on physical
modification of the urban area. In addition to that, most of the building material has good
thermal conductivity and storage capacity. In simple word, the material with high thermal
conductivity quickly transfers the heat inside itself, and if the material has the thermal
capacity it can store more amount of heat in its body [10].
2.3 Net Radiation
The net radiation on the earth surface is shaped by following four distinct radiations: 1) The
solar radiation is an amount of the energy radiated from the sun. The solar radiation can be
affected by metrological properties such as season, cloud cover, air pollution, and etc. 2) The
solar reflectance (albedo), the amount of solar energy reflected from the surface is the solar
reflection. The amount of solar reflectance is highly dependent on the surface materials. 3)
The atmospheric radiation is an amount of the heat emitted by particles in the atmosphere.
A warm atmosphere with the dense particles contained more energy to emit. 4) The surface
radiation is the heat radiated from a surface itself. The surface radiation highly depends on
the temperature of the surface and its surrounding [10].
In the urban area, dark-colored materials include road, roof, pavement and etc. are
minimized on albedo. Besides that, the urban geometry and level of air pollution as a
catalyzer are contributing to increase of the amount of net radiation in the urban area.
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Based on the given statement, it can be expected to see a high amount of net radiation in an
urban area in comparison to the rural context.
2.4 Convection
The convection is a vertical interchange of the energy. It can occur in the liquid and gas
forms. The convection can be intensified in the high wind speed and the turbulent air over
the rougher surface. It can be intensify too when there is a temperature difference between
the surface and the air [10, 11]. It is interesting to know, the physical modification of the
urban area like emerge of the UHI phenomenon can be intensified in the calm and clear
meteorological context. For instance, loss of air turbulence increases the heat capacity in the
daytime. Apart from that, the urban geometry significantly contributes to the air turbulence
and wind speeds. It can be stated that an urban area is responsible for decrease and increase
of the convection [5, 10].
2.5 Anthropogenic Heat
It is mainly released as result of the human indoor/outdoor activities. The source of it can be
found in many urban and rural contexts. The primary sources for the anthropogenic heat
release are the heating system, the engine combustion, the creature’s metabolism, and etc.
[2, 10, 11, 12]. The human activities significantly contribute to the release of the
anthropogenic heat [10]. Apart from that most of these activities are located in the urban
area [13]. In this sense, Marsh & Grossa (1996) believed that population density from one
side and the land-use from another side are important parameters for the amount of
anthropogenic heat. Based on their own study in the urban area the amount of the
particulate matter was five times higher than the rural and at least three times greater than
the suburban area [12]. Furthermore, the traditional study concludes that the gains of
anthropogenic heat in the winter is more than the summer. Unlike, the recent study found
that the air conditioner dependency can intensify the gains of anthropogenic heat in the
summertime [10].
3 Discussion
The current explanatory study in its own scope figures out that, the unmanaged rapid urban
development is mainly responsible for the physical modification of the urban area. This
modification can vary from urban climate, air pollution, UHI and etc. So far, several studies
have focused on the buildings, materials and/or regional scale, while there is no agreed
method and tools to examine the physical modification at the neighborhood and/or the
microclimate scale.
For instance, most of the regional study scale done by the use of remote sensing data
technologies. Likewise, different programs based on the study objective developed for the
building scale. However, this situation is different for the neighbourhoods and/or the
microclimate scale. Lack of a comprehensive method for measurement makes process
complicate. Therefore, most of the study try to use specific dimension for their study and
they offer their own model. Of course, recently some institutes and communities started to
develop the program such as Envi-Met and Grasshopper plugin. However, these programs
are at begging or trial stage. Apart from that, mostly able to study in specific dimensions,
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while the physical modification of the urban area at local scale has several dimensions and
this provides a great challenge to cover all of them [3].
Therefore, to solve this problem, based on the energy balance equation Eq. (1) the following
criteria should be considered for assessing the modifications of urban areas: The Urban
Form, The Urban Material and The Urban Population. The given dimensions are highly
associated with the energy balance equation Eq. (1) and any modification on each
contributes to the physical modification of the urban area.
Urban Form
In the urban form to define a space, the building used as a wall and the street used as a
floor. The repetition of these elements together creates the urban form [2, 6, 11, 14]. The
urban climatologist tries to classify the form of city based on the buildings height, street
width, density and scale of the local neighborhood. The combination of these elements from
one side contributes to the loss of longwave radiation at night time and from another side
increase the solar absorbance at daytime. Apart from that, the urban form significantly
contributes to modification of the airflow and wind speed [2, 3, 15, 16].
Furthermore, the height of building and width of street together define the aspect ratio and
sky view factor (visibility of sky as a fraction from the middle of the street). This is an
important factor to adjust the amount of solar radiant penetration. Moreover, the street
orientation itself significantly associated with the solar radiation and air movement [3, 6,
15]. The following Figure 3 provides a better vision to the urban form.
Figure 3. The Urban Form
Urban Material
The urban material includes the pavement, roof and wall are usually applied by the
architecture due to various reasons like cost, durability, appearance, and etc. Certainly, each
of these materials has a specific influence on the urban hydrological and the thermal
balance. Furthermore, the physical modification of the urban area at microscale is
dependent on the absorptivity and the thermal admittance of the surface [15].
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According to the Akbari, Pomerantz, & Taha (2001), the thermal energy balance can be
efficiently adjusted if the high albedo material and soft surface include the plant and the
vegetation applied in the urban area [17]. From another point of view, the surface material
changes are cost efficient since the new material can be easily applied to the current
structure. Apart from that, with the new technology architecture is not limited to white color
because the new material is modified high reflectivity and emissivity too [16].
The Urban population
As stated before head, the main source of the anthropogenic heat is human activity, the
majority of this activity is located at the centre of the urban area too [12]. Therefore,
population growth means increase of the number of the consumer which contributed to
release the high amount of the anthropogenic heat. Apart from that, the population growth
requires new towns. In this situation, if new construction irrespective of the urban form and
materials developed, it can be negatively affected due to the physical modification of the
urban area.
4 Conclusion
This study based on the contemporary literature tries to figure out the relation of the rapid
urban development with the physical modification of the urban area. In this sense, the
current study found that un-controlled urban development responsible for the physical
modification of the urban area includes urban climate, air pollution, UHI and etc. Moreover,
the current study believes that, majority of the study consider the physical modification of
the urban area on regional and/or building scale. Therefore, a lack of microscale study is
latent. On the other it is believed, that the microscale is an effective scale which contributes
to the physical modification of the urban area. However, lack of appropriate methodology
from one side different variables and aspect from another side made it impracticable. This
study based on the energy balance equation tries to make an attempt to assess the physical
modification of the urban area by considering the urban form, urban material and
population.
Acknowledgements
I would like to acknowledge Canay ATAÖZ Head of Technical Service of Library at the Eastern
Mediterranean University to provide the resources necessary for this study.
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Population growth and urbanization lead to urban heat island (UHI) phenomenon. Urbanization is occurring at a very high rate in the Surat city. Thus, the study of the urbanization impact on the UHI effect for the Surat city is performed in the present study through studying the impact of land use land cover on the land surface temperature of urban and sub-urban areas of the Surat city over the period May 1998 to May 2018. Also, these effects are compared with that of a nearby sub-urban taluka Kamrej, which showed that temperature in urban areas is more than that of the sub-urban areas. Aforesaid facts clearly showing the existence of the UHI effect in the Surat city. As urbanization contributes to climate change, its effects on rainfall are studied by comparing rainfall trends of urban and sub-urban areas of the Surat city and nearby sub-urban area Kamrej. Trend analysis showed that trend magnitude values are higher for the urban areas than sub-urban areas, indicating that UHI effect increases rainfall in urban areas. Hotspot analysis is also performed for the Surat city corresponding to May 2018 to recognize hot spots and cold spots. As the Surat city is highly urbanized, thus, hotspots are more than cold spots.
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Knowledge of the day-to-day dynamics of surface urban heat island (SUHI) as well as their underlying determinants is crucial to a better design of effective heat mitigation. However, there remains a lack of a globally comprehensive investigation of the responsiveness of SUHI variations to meteorological variables. Based on the MODIS LSTs and auxiliary data in 2017, here we investigated 10,000+ cities worldwide to reveal day-to-day SUHI intensity (SUHII) variations (termed as SUHIIdv) in response to meteorological variables using Google Earth Engine. We found that: (1) meteorological variables related to the thermal admittance, e.g., precipitation, specific humidity and soil moisture (represented by daily temperature range in rural area, DTRr), reveal a larger regulation on SUHIIdv than those related to the air conditions (e.g., wind speed and near-surface air temperature) over a global scale. (2) Meteorological regulations on SUHIIdv can differ greatly by background climates. The control of specific humidity on SUHIIdv is significantly strengthened in arid zones, while that of wind speed is weakened prominently in equatorial zones. SUHIIdv is more sensitive to soil moisture in cities with higher background temperatures. (3) All meteorological variables, except that related to soil moisture (DTRr), show larger impact on SUHIIdv with antecedent precipitation over the global scale. Precipitation is observed to mitigate the SUHIIdv globally, and such effects are even more pronounced in equatorial and arid zones. We consider that our findings should be helpful in enriching the knowledge of SUHI dynamics on multiple timescales.
Thesis
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The phenomenon urban sprawl is accompanied by significant impacts on the envi-ronment, as it is linked with unorganized and unhindered urban growth and aimless landscape development. Though these negative effects on the environment might not be clearly visible in everyday life in industrialised countries of the world, they are especially omnipresent in the global south. In order to be able to develop an understanding of the current state and possible trends of the city, the drivers and implications of the urban sprawl in the respective study area must be identified. The Kathmandu Valley (KV) was chosen as the study area, because of the geographical setting of the region, which results in special circumstances due to limited land availability. In the present thesis, the Kathmandu Valley is investigated for urban sprawl via remote sensing. Furthermore, field work from 10/2019 to 12/2019 allowed to collect additional data. Thus, an analysis of the current state of the Kathmandu Valley as well as a comparative analysis of satellite images in the time period from 1989 till 2019 will be performed. The following questions should be clarified in the study:  How did the urban sprawl in the KV develop in the recent decades?  What drivers can be identified for the development of urban sprawl in the KV?  Which implications result from this and how are these problematic for the envi-ronment and the society?
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More than half of the world’s population now lives in urban areas, and trends in rural-to-urban migration are expected to continue through the end of the century. Although cities create efficiencies that drive innovation and economic growth, they also alter the local surface energy balance, resulting in urban temperatures that can differ dramatically from surrounding areas. Here we introduce a global 1 km resolution data set of seasonal and diurnal anomalies in urban surface temperatures relative to their rural surroundings. We then use satellite-observable parameters in a simple model informed by the surface energy balance to understand the dominant drivers of present urban heating, the heat-related impacts of projected future urbanization, and the potential for policies to mitigate those damages. At present, urban populations live in areas with daytime surface summer temperatures that are 3.21 ∘C (−3.97, 9.24, 5th–95th percentiles) warmer than surrounding rural areas. If the structure of cities remains largely unchanged, city growth is projected to result in additional daytime summer surface temperature heat anomalies of 0.19 ∘C (−0.01, 0.47) in 2100—in addition to warming due to climate change. This is projected to raise the urban population living under extreme surface temperatures by approximately 20% compared to current distributions. However we also find a significant potential for mitigation: 82% of all urban areas have below average vegetation and/or surface albedo. Optimizing these would reduce urban daytime summer surface temperatures for the affected populations by an average of −0.81 ∘C (−2.55, −0.05).
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Australia's first in-depth statutory inquiry into the health impacts of climate change, covering both mitigation and adaptation. It sets a blueprint for the coming decade (2020-2030) for the Western Australian health system to support health services to do more to reduce emissions and waste without compromising the quality of patient care, and to adapt to climate change and protect the health of the community. It recommends the establishment of Australia's first Health Sustainable Development Unit to help drive the needed change. Available at https://ww2.health.wa.gov.au/climate-health-wa-final-report
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The quality of life of millions of people living in cities can be improved if the factors that affect the urban microclimate are understood and the form of the city responds to them in a manner that is appropriate to its location. Underlying this approach is the idea that climatically responsive urban design is vital to any notion of sustainability: it enables individual buildings to make better use of 'natural' energy, it enhances the potential for pedestrian comfort and activity in outdoor spaces, and it encourages city dwellers to moderate their dependence on air-conditioned buildings and private vehicles (Erell et al, 2010). This paper suggests principles for successful integration of climatic strategies in urban planning processes, and provides case studies illustrating their implementation in practice.
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Progress in urban climatology over the two decades since the first publication of the International Journal of Climatology is reviewed. It is emphasized that urban climatology during this period has benefited from conceptual advances made in microclimatology and boundary-layer climatology in general. The role of scale, heterogeneity, dynamic source areas for turbulent fluxes and the complexity introduced by the roughness sublayer over the tall, rigid roughness elements of cities is described. The diversity of urban heat islands, depending on the medium sensed and the sensing technique, is explained. The review focuses on two areas within urban climatology. First, it assesses advances in the study of selected urban climatic processes relating to urban atmospheric turbulence (including surface roughness) and exchange processes for energy and water, at scales of consideration ranging from individual facets of the urban environment, through streets and city blocks to neighbourhoods. Second, it explores the literature on the urban temperature field. The state of knowledge about urban heat islands around 1980 is described and work since then is assessed in terms of similarities to and contrasts with that situation. Finally, the main advances are summarized and recommendations for urban climate work in the future are made. Copyright © 2003 Royal Meteorological Society.
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The need to respond to the rapidly changing city climate is particularly urgent in the tropics where the urban transition is currently at its peak. While the need is clearly felt by the tropical urban dwellers, texts that provide an overview of the problem and indicate possible design solutions are rare. This comprehensive reference will be welcomed by student and practising architects as well as other built envronment professionals engaged with the environmental effects of building in worldwide warm and humid climates.
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The beneficial influence of trees and water ponds on summer comfort in urban spaces was studied experimentally in situ and in wind tunnels but the modeling needs further development to become effective in practical applications. This paper introduces a numerical approach based on coupling the CFD model of airflow, in which the influence of trees is considered as source terms, and the radiation exchange, completed with thermal conduction. The CFD, radiation and thermal conduction models use the same discretization grid at their common boundaries. The model was used to estimate the influence of trees and water ponds in a real town square. Comparison of results between two situations, with and without vegetation and water pond, indicate that surface temperatures are reduced in presence of trees and the comfort is improved.