eco system & built environment

7/24/2019 Eco System & Built Environment

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TRANSFORMATION OF ECOLOGICAL CONDITION IN URBANNEIGHBOURHOODS DUE TO DENSITY VARIATION

ARCH- 6106Ecosystem And Built Environment Design

STD No : 0412012010


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TRANSFORMATION OF ECOLOGICAL CONDITION IN URBANNEIGHBOURHOODS DUE TO DENSITY VARIATION

Abstract

The paper will focus on the comparative analysis on the ecological states of low to high density

neighborhoods of the urban context and the maximum satisfactory level of the users for the each type

of ecological state. The presence of different types of ecological elements and their relationship to the

built elements will be studied to understand the effects over user satisfaction. The amount of

vegetation present in a certain urban neighborhood and their positions will be listed to identify the

changes of ecological condition and level of satisfaction. Gross land use and land cover of different

neighborhoods will be another prior research to understand the ecological state. Finally, the paper

will focus on taking into account of the inherent values of environmental stability for urban

neighborhoods and design techniques and will facilitate creation of communities which are more

sustainable socially.

Keywords

Urban neighborhoods, ecological condition, user satisfaction, vegetation

Introduction

For sustainable living the urban environment needs to be in a balanced state. The density of an urban

neighbourhood should be such as so the residents of that neighbourhood may live a healthy life. To

identify the balanced state of healthy living it is necessary to know the transformation of urban

ecological conditions along with the variations of different elements of the neighbourhood. In Dhaka

city it is observed that, rapid urbanization has drastically changed the ecological conditions and so

that the urban neighbouhoods have also transformed in a state that the environment can not sustain

the biodiversity in a balanced way.

The paper focus on the transformations that occurs due to density variations in urban

neighbouhoods. To identify the transformations, the study of the urban neighbouhood is to be done

and so that the density of different areas is to be measured. The proportion of built area and green

area change according to the density variation of the urban neighbourhoods. The conversion of

infrastructures is being done to facilitate the increased population in urban neighbourhood. But the

conversion hampers the natural state of ecological balance if it is not done under appropriate

supervision to maintain the balanced state.


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Definitions

Urban Area

An urban area is characterized by higher population density and vast human features in comparison

to areas surrounding it. Urban areas may be cities, towns or conurbations, but the term is notcommonly extended to rural settlements such as villages and hamlets. Urban areas are created and

further developed by the process of urbanization. Measuring the extent of an urban area helps in

analyzing population density and urban sprawl, and in determining urban and rural populations.

Neigbourhood

A neighbourhoodis a geographically localised community within a larger city, town or suburb.

Neighbourhoods are often social communities with considerable face-to-face interaction amongmembers. "Researchers have not agreed on an exact definition. Neighbourhood is generally defined

spatially as a specific geographic area and functionally as a set of social networks. Neighbourhoods,

then, are the spatial units in which face-to-face social interactions occur the personal settings and

situations where residents seek to realize common values, socialize youth, and maintain effective

social control.

Urban Environment

The urban environment refers to environments dominated by high-density residential and

commercial buildings, paved surfaces, and other intense human influences, which create a unique

landscape dissimilar to many previously studied environments in the field of ecology.

Urban Ecology

The scientific study of the relation of living organisms with each other and their surroundings in the

context of the proposed urban environment. Firstly, It describes urban design program or design thatincorporates political, infrastructure (roads, sewer etc.) and economic considerations in a balanced

manner. Secondly, it refers to the area of biology that is concerned with urban areas in terms of

relationships, interactions, types and number of species found within urban habitats.

Urban ecology posits that the urban realm is made up of four interrelated variables: a functionally

integrated population, a self-sustaining system of relationships, an urban environment, and the

technology and tools which sustain the community. A change in one will bring about a change in

the other three.


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Objective Of The Paper

The basic objective of the paper is to figure out the relationship between the transformation of urban

ecology and the population density. In Dhaka city, the rapid urban growth has influenced the density

of the neighbouhoods. In recent years the density has increased in an enormous proportion. To

facilitate this increased population the infrastructure of urban neighbouhoods has been changed and

so that the urban ecological condition has been transformed.

In developed countries, it is seen that about 75% of urban area is retained for urban open space. So

that, the biodiversity can sustain. But in our Dhaka city the open spaces contain less than 15% where

the marginal recommendation is 25% of the total land area. The increase of density results in the

increase of built area occupying the urban open spaces and soaking surfaces. Moreover, the need of

transportation facilities of the increased population is satisfied by occupying green areas. This

transformation causes the biodiversity degradation. In unplanned neighbouhoods this degradation isa serious problem because the infrastructure is not designed here. It is hoped that in planned

neighbourhoods of Dhaka city, the ecological state will remain balanced in spite rapid population

growth. Bu the degradation of biodiversity is also present here. To understand this causes the

elements urban ecology should be studied.

The understanding of this transformations needs the recognition of the elements that are responsible

for the transformations. The elements of biodiversity and sustainable urban environment is to be

identified and their changing patterns should be studied. This study will help to design the urban areaby organizing the elements to keep the urban environment in a balanced state. The effects of the

transformation can be assumed by this study so that the appropriate measures can be taken while

making any changes in the urban environment.

Methodology

The transformation of ecological state is a huge area of study because the transformation can

occur in a number of ways and in different time zones. Moreover the transformation is not same in

all types of neighbourhoods. The proportion of changes is not parallel in different part of a

certain neighbourhood. So, the end result of the study will differ from one urban neighbouhood to

another. Initially the basic concept of study may remain same but the detail surveying methods

and analysis may vary from one neighbourhood to another.

The procedure of the study can be described in three stages. The initial stage is the selection of

study area and identify the pattern of the area, its urban design features, infrastructure, built

environment and vegetation proportion, water drainage system, soaking areas etc.


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Secondly, the density variation of different zones within the same infrastructure will be measured.

Along with that the changes of infrastructure that is done to facilitate the increased population will

be studied. The changes of proportion of built area and vegetated area, transformation of

drainage system and proportion of soaking area will be monitored to understand the

transformation of urban ecology.

Finally, The overall area of transformation and pattern of the changes will be identified and the ratio of

urban ecological elements present in the neighbouhood will be examined.

Study Area Selection

Initial Stage

Identification OfInfrastructure

Built Area

Green Area

Open Space

DrainageSystem

RoadNetwork

Identification OfDensity Variation inSame Infrastructure

Identification OfTransformation OfInfrastructure

Final Stage

Overall AssumptionsOf Density Variation

Overall AssumptionOf EcologicalTransformation

Analytical Stage


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Selection Of Study Area

The area is selected for the study considering some basic criteria.

the neighbourhood must be a planned urban areathe area should have planned infrastructure such as planned road network, storm water

drainage, proper planning for maximum built area, green area and open spaces, urban park,

adequate setbacks etc.

According to this criteria two sectors of Uttara (Sector-4 and 6) is selected. In the last few years

the urban neighbouhoods of Uttara is developed rapidly and density of population has increased

tremendously. Though the neighbourhood is planned as such that the area could sustain the

biodiversity but it has been experiencing some transformation of urban ecological state. In some

part of this two sectors the ecological conditions remain stable though density change has been

occurred but in some other areas the condition is getting worse.

Figure 1 : Uttara Sector -4(left) Sector-6(right)

Dhaka-Mymensingh Highways

Main Artery Roads

Secondary Roads (with footpaths on bothsides)

Tertiary Roads (without fottpaths)


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Basic Informations Of The Selected Sites

The density of urban neighbourhood changes according to residential units in divided plots. the area

is planned with an organized infrastructe of plots, road networks, green belts, open spaces like parks

waklways and so on. The basic information of the area is given below

Plot Distribution

The plot size of Uttara sector-4 and sector -6 is generally 5 kathas(3600 sft). these are basically

residential plot size. while the plots of more than 10 kathas are situated along the tertiary roads.

Moreover there are some reserved plots of large size for the community services like school college

and hospital. The large plots are also developed for commercial use along the Dhaka-Mymensingh

Highways.

Road Networks

The road width of these two sectors is roughly three types. The Main artery Roads, the secondary

roads with footpaths on both sides and the tertiary roads without any footpaths. The main roads are

60 ft wide in average. The secondary roads are 30-40 ft wide and the tertiary roads are 20-30ft wide.

The main roads have 30 ft wide green belts on both side which acts as a green boundary between

roads and residential plots.

Open Space

There are some reserved plots which is developed as urban parks and playfields in sector-4 and

sector-6. The parks become the biodiversity hotspots for the species that are found in urban

neighbouhood. The footpaths of the secondary roads have large trees and soft paves in some parts.

Ecological Transformation And Density Variation Analysis

The density of the population depends on the number of family units live in a single plot. According to

RAJUK authority it is allowed to build up to six storied residential building on the plots of five kathas

which have 20-40 ft road width that are reserved for residential developments. At the initial stage the

plots are owned by a single person and the residence that were built was a single family dwelling. But

in recent years The buildings are constructed by developers and they used to build six storied

residential building with units on each floor leaving the ground floor for car parking space. If there is 5

persons in average in a family then the population increases from 5 to 50 in a single plot. this practice

is widely seen at the adjacent plots of main artery roads where commercial developments like

shopping centers, supermarkets and banks are in a walking distance and near the urban community

facilities like school college, hospitals and urban parks.


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soakable surface

vegetation

single family residence

20 ft wide road

water drain

soakable surface

vegetation

6 storeyfamily residence

20 ft wide road

water drain

Figure 2 : Proportion of Built area and Green area due to density variation

The soakable surface that exists in single family residence is reduced to almost zero and the

egetation is made artificially which is not adequate in prrportion. It is seen that, in a single family

residence there are 40% built area and 60% open area is present where in a six storied building there

are 75% built area and only 25% open area is present. The 25 % open area is not always kept as

soakable green and the vegetation is not maintained by the dwellers. The plantation of potted plant is

practiced by the apartment dwellers.

single family residence 6 storeyfamily residence

soakablesurface

vegetation

coveredwater drain

40 ft wide road

soakablesurface

vegetation

water drain

30 ft wide road

Figure 3 : Changes of Built area and Green area and drainage system due to density variation

The population growth has increased the number of vehicles running on the internal roads of the

neighbourhoods. The single family residence own only one car where in a six storied building theremay be 6-8 cars. Thus the number of vehicles increased to eight times for a single plot


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4storiedresidentialbuilding

4x5=20occupancy(appx.)

1-2storiedresidentialbuilding

5-6

occupancy(appx.)

greenarea(backyard)

greenarea(lawn)

greenarea

greenarea(bufferarea)

uncovereddrainage

low

frequency

vehicularmovement

non soakable areasoakable surface

non soakable areasoakable soakable surface

non soakable area

non soakable areasoakable

non soakable area soakable

non soakable area


5x2x5=50occupancy(appx.)

coveredarea(setback)

greenarea(buildingvegetation)

greenarea(buildinglandscape)

uncovered

drainage

higherfrequencyvehicularmovement



uncovered

drainage

Figure 5 : Proportion of Built area and Green area due to density variation

Figure 4 : Proportion of Built area and Green area in same plot size


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non soakable area

soakable

non soakable area non soakable areasoakable



setback


rainwaterdrainage

pedestrianpath

uncovereddrainage


uncovereddrainage


4

x5=20occupancy(appx.)

setback

pedestrianpath


non soakable area non soakable area



buildinglanscape

rainwaterdrainage

pedestrianpath

pedestrianpath



buildinglanscape

Figure 6 : Widening of Secondary roads by reducing width of footpaths and green area

The increase of population density has caused increase of number of traffics and so that the widening

of roads become a necessity. For doing that the existing 30 ft wide road is widened to 40 ft and 10 ft

wide footpaths are reduced to 5 ft and in some places the water drains are covered and the footpaths

are made over the drains. The large trees that existed on the roadside are cut down in some places

and hence the proportion of vegetation is reduced


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Figure 8 : Transformation of infrastructure

Figure 7 : Widening of Secondary roads by reducing width of footpaths and green area

The main artery roads are seperater from the plots with green belts of 30 ft width on both sides and

there area footpaths and water drainage systems along with the plots. The plot size is larger than the

residential ones and they were developed as mixed use or commercial in most cases. So the building

needed exposer and service area in front of the plot facing the main road. To provide this facility the

green belt is reduced in some parts along with the plots. Therefor as supportive facility car parking

area is created. Now this situation is that the vendors occupied some parts of the green belt also.

Therefore the total green belt is reduced to 50% from the actual area.

water drain

footpath

green belt

main artery road

soakable surface

commercialbuildings

covered water drain

footpath

temporary structures(vendors, teastall)

main artery road

soakable surface

commercial

buildings

car parking and storage

extension ofcommercial buildings

outlet of water drain


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non soakable area

soakable


non soakable area



setback


rainwaterdrainage

pedestrianpath

uncovereddrainage


uncovereddrainage



setback

pedestrianpath

non soakable area

soakable


non soakable area


5x2x5=50occupancy(appx.

)

setback

rainwaterdrainage

pedestrianpath

covereddrainage

greenareaconvertedinto

supportivecommercialfunctions

covereddrainage

15storiedcommercialbuilding


setbackconvertedintoshops

pedestrianpath

greenareaconvertedinto

supportivecommercialfunctions

The drainage system that are present along the main artery road is being covered at the access point

of the buildings. The footpath is widened also by covering the drain with slabs so the outlet is

minimized. Some extensions are built in recent years to facilitate the main buildings which reduced

the soakable surface of the plots. The green belt is also helpful to soak the rainwater but reduction of

that area has created an extra pressure over the water drainage system.

Figure 9 : Transformation of infrastructure along the main artery roads


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The survey shows that the reduction of green area is very high along the connecting roads of the

Dhaka-Mymensingh Highway. The road widening and reduction of footpath width is seen where there

are residential plots on both sides of the roads. The roads that have parks on one side are changed at

all. The roads that have school and colleges have widened much and the drainage system is taken

completely underground. But the school fields are protected by the authority so those can be possible

opportunity for maintaining biodiversity. The fields also provide the necessary surface for rain water

soaking and the trees along the boundary of the school compound can play an important role to keep

the balance of green urban area.

School Compound

Figure 10 : Destruction of green belt and water drainage system

Urban Parks

Dhaka-Mymensingh Highways

Transformation occurred on the roads

Figure 11 : Degradation of ecological condition due to increase of population density


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Conclusions

The overall survey indicates that, the increase of population density will hamper the urban

ecological balance. The increase of density also encourage the increase of number of traffic

which create a bad impact on natural state. the present infrastructure is suitable for present

density but it will be alarming if the density rise without any control. So it is necessary to thinkabout the density control and to restore the environment of urban neighbourhood to its actual

designed state. To do so some actions should be taken by the concerned authority.

The allowable building size and apartment number should be reduced considering the location so

that it will not create pressure on the existing road width. The vegetation area and green belt

should be protected by laws and the large trees should be maintained. The roadside trees should

be protected and nurtured. The internal soakable areas of the plots should be designed as such

so that it can get enough open space to get rain water. The drainage system should be protectedas it was designed and there should be a layer of vegetation between footpaths and drain if

possible so that the drains will no tbe encroached or covered by the adjacent dwellers. The

commercial settlements should be monitored so that they will not occupy the green belt and the

drain area for their service purpose. The allowable commercial use facing the green belt should

be prohibited to protect the zone from encroaching. There should be a thorough survey and study

to find the detail information of each and every corner of the total zone, so that the specific

problems of each individual plot and road can be identified and appropriate measures can be

taken. This study will help to design future extension of the neighbourhood or a new urban

neighbourhood in a way so that it will sustain the biodiversity in a ecologically balanced state.


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References

The status of urban landscape and urban environment in DhakaQazi Azizul Mowla

Department of ArchitectureBangladesh University of Engineering & Technology(BUET)Dhaka, Bangladesh

Eco-design and planning for sustainability in urban Dhaka

Changes in the traditional urban form and the social sustainabilityof contemporary cities: A case study of Iranian citiesAyyoob Sharifi, Akito MurayamaDepartment of Environmental Engineering and Architecture, Graduate School of Environmental

Studies, Nagoya University, D2-1(510) Furo-cho, Chikusa-ku, Nagoya,Aichi Prefecture 464-8601, Japan

Social ecology, sustainability, and economicsRaul P. Lejano(a), Daniel Stokols (b)a Department of Planning, Policy, and Design, School of Social Ecology, SE-I, Room 218G,University of California, Irvine, Irvine, CA 92697-7075, United Statesb Department of Planning, Policy, and Design, Department of Psychology and Social Behavior,School of Social Ecology, SE-I, Room 206C, University of California, Irvine,Irvine, CA 92697-7075, United States

Professor and Head of

Qazi Azizul MowlaProfessor and Head of Department of ArchitectureBangladesh University of Engineering & Technology(BUET)Dhaka, Bangladesh

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