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WORKING GROUP

Center of Excellence IINTEGRATED LANDUSE PLANNING AND WATER RESOURCES MANAGEMENT (ILPWRM)

Project Investigators

Prof. Arup Kumar Sarma, Principal InvestigatorCivil Engineering Department, Indian Institute of Technology Guwahati

Prof. Chandan Mahanta, Co-Investigator

Civil Engineering Department, Indian Institute of Technology Guwahati

Dr. Rajib Bhattacharya, Co-Investigator


Dr. S. Dutta, Co-Investigator


Dr. S. Kartha, Co-Investigator


Dr. Bimlesh Kumar, Invited Member


Dr. Sreeja P., Invited Member


Project Staff

Ms. Banasri Sarma, Senior Research Fellow

Ms. Juri Borbora Saikia, Senior Research Fellow

Ms. Plabita Barman, Senior Research Fellow

Mr. Debajit Bora, Junior Research Fellow

Mr. Ankuran Pathak, Junior Research Fellow

Mr. Avijit Deka, Junior Research Fellow

Mr. Subhasish Das, Junior Research Fellow

Mr. Pinku Jyoti Baishya, Junior Research Fellow

Ms. Rubi Kakoti, Office Assistant

Mr. Mridul Deka, Field Assistant

Mr. Dimpal Das, Field Assistant

Mr. Anjal Bezbarua, Field Assistant

Mr. Gautam Boro, Field Assistant

Mr. Biswajit Das, Field Assistant

Shri Arun ChandraThakur, Town Planner

Published by

Centre of Excellence

Civil Engineering Department, IIT Guwahati

Guwahati : Assam : India

All rights reserved by the Publisher

Year of publication 2012

IINTEGRATED LANDUSE PLANNING AND WATER RESOURCES MANAGEMENT (ILPWRM)A centre sponsored by Ministry of Urban Developement, Govt. of India

Foreword

Urbanization is increasing at an alarming rate all over the world. In the developing country, urbanization, generally starts and expands in an unplanned manner leading to an ecological imbalance, which many a time converts urban areas into a multi-hazard zone. Such unplanned urbanization may also affect its periphery adversely. A far sighted developmental planning only can lead to a hazard free ecologically sustainable urbanization. If we continue with haphazard development without taking much care about their impacts on the ecosystems, we will end up having extremely hazardous urban areas that may reach an irreversible status, by crossing its carrying capacity. If population increases beyond carrying capacity, the resources available become insufficient to support such growth and environment starts reacting in the form of hazards to bring down the population to a bearable level. Therefore we need to make developmental plan giving due importance to and having clear concept of urban carrying capacity.

This document aims at giving a concept of urban carrying capacity and its estimation principles. Emphasizing the ultimate objective of developing a sustainable hazard free urban area, a new method of computing carrying capacity by analyzing adverse impact of population growth on the urban environment is also presented in this document.

A.K.Sarma Principal Investigator CoE (ILPWRM)

Indian Institute of Technology Guwahati

CONTENTS

Title Page No. Foreword

1. Introduction 3-5

1.1. Concept of carrying capacity 3

1.2. Sustainability and carrying capacity 4

1.3. Significance of carrying capacity 5

2. Urban carrying capacity 6-13

2.1. Urban area and carrying capacity 6

2.2. Concept of bioregion 7

2.3. Levels of carrying capacity evaluation in an urban area 7

2.4. Calculation of urban carrying capacity 9

3. SAFE carrying capacity model proposed by IIT Guwahati (CoE ILPWRM) 14-22

3.1. Introduction 14

3.2. Framework for calculation of carrying capacity 15

3.3. Application of the Concept to practical field: A case study of a pilot 17 watershed in Guwahati City of Assam, India

References 23

Chapter 1

INTRODUCTION

1.1. Concept of carrying capacity

The carrying capacity concept was pioneered by Thomas Malthus in the year 1798. He predicted

that the earth can only hold a definite amount of human growth for a definite time. This concept

holds a crucial position in determining the quality and state of an ecosystem with respect to the

pressures meted by the demands of the dwelling population. It is basically an ecological concept

that also embraces the socio-economic parameters.

If we go on defining carrying capacity then it will be a herculean task because the concept itself is

very vast and has different perspectives, like social, cultural, political, ecological etc. In simple

terms, the carrying capacity of an area can be defined as the maximum number of people that can

be supported by the environment of that area through optimum utilization of the available

resources.

In other words carrying capacity of an area refers to an extreme limit. This limit defines the

population carrying capacity of the area. If this limit is crossed then the nature will react by

imposing pressure to resist the abrupt growth and development of the people resulting into

equilibrium. These pressures can be in the form of floods, droughts, landslides, famine etc.

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Department of Civil Engineering, IIT Guwahati Centre of Excellence ILPWRM |

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Fig 1: Graph showing the relation between population rise & carrying capacity

Over shooting population

Enhanced carrying capacity

Degraded carrying capacityStable population

Carrying capacity

Po

pu

latio

n (

N)

Time (T)

Carrying capacity graph© CoE ILPWRM IITG

Carrying capacity is not fixed. It can increase or decrease phenomenally. There are many factors that can influence the carrying capacity of a region. The pattern and extent of resource usage serves to be the primary factor that affects the carrying capacity a lot. This indeed depends highly on the socio-economic status of the people. Secondly, the use of technology also influences the carrying capacity, i.e. if technology is used in a positive manner than definitely the carrying capacity will get increased manifold or may be degraded vice versa. Fig-1 shows the plot of population growth with time and various ways that the population can reach the carrying capacity.

1.2. Sustainability & carrying capacity

Ensuring sustainability of the resources is one of the biggest tasks of humankind for humankind. The sustainability of an environment can be understood as its endurance capability, i.e. making the resources available for usage forever. So, it can be well said that sustainability can be measured by the carrying capacity. It is so because if the maximum limit of resource is known then only an efficient usage policy could be formed that will ensure future availability of the same.

Sustainability has three foundation bases; they are social, economic and environmental. So, it is always advisable that the development people want should be sustainable or simply sustainable development through adequate emphasis to all these three pillars and their interactions so that an inherent balance can be maintained. Thus sustainable development indirectly govern the carrying capacity.


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Fig 2: Diagram showing the interaction between the three pillars of sustainability

ECOLOGY

BEARABLEVI

ABLE

EQUITABLE

SUSTAINABLE

ECONOMYSOCIETY

© CoE ILPWRM IITG

1.3. Significance of carrying capacity

The world is developing by leaps and bounds. Development is taking place at a faster pace. impact of this ever-increasing population-base combined with dangerously depleted natural

resources highlights the urgent need for changes in human lifestyles and land-use patterns (Lane, 2009). However, it becomes imperative to know the limits up to which development is feasible. The Ecological Footprint Atlas (2008) says, “We cannot make meaningful decisions about where we need to go before we know where we stand”. Thus there is an urgent need to locally estimate the carrying capacity. The carrying capacity concept can be utilized in planning and development of urban areas to keep a balance between built environment and natural environment which is currently a challenging task. Under prevailing socio-economic conditions, the application of carrying capacity concept enables to determine the optimum population that can be supported within a given area with adequate infrastructure facilities so that development is environmentally hazard free and sustainable.

As such the

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URBAN CARRYING CAPACITY : CONCEPT AND CALCULATION

Chapter 2

URBAN CARRYING CAPACITY

2.1. Urban area & carrying capacity

An area is referred to be “urban” when it possesses features like high population density coupled with great infrastructure facilities. The probable definition of an urban area varies significantly between nations. In India, The Census of India, (1971) defines urban areas as :

i. All places with a Municipality Corporation or Cantonment or Notified Town Area

ii. All other places which satisfied the following criteria :

a. A minimum population of 5,000.

b. At least 75% of the male working population should be non-agricultural.

c. Density of population is at least 400 per sq. Km. (i.e. 1000 per sq. Mile)

With an upsurge in economic growth, many rural areas, farmlands, country sides etc are getting converted into urban sprawls. Development is transforming natural sites into built up area. The process of urbanization seems inevitable as cities and towns are growing exponentially with increasing demand for urban area. The urban areas are the entities which have great potential of exceeding the local carrying capacity because they require enormous concentrations of food, water, and materials in a small area. The concentration requirements may go far beyond the level provided by the local carrying capacity. Also this high degree of consumption is associated with huge quantity of waste production and sewage which cannot be properly assimilated within the local carrying capacity (Aspeslagh, 1994).

So, it is quite evident that urban ecosystems are the ones that are highly prone to these so called, “irreversible damages”. To ensure more equitable and sustainable land-use patterns, human ecologist Garrett Hardin (1986) recommends directly linking and limiting populations to the regions which sustain them.

The urban carrying capacity can be defined as the level of human activities, population growth, patterns & extent of land use, physical development, which can be sustained by the urban environment without causing serious degradation and irreversible damage (Oh et.al., 2002).


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2.2. Concept of Bioregion

A “Bioregion” is a cumulative term. It's a huge region that embraces an urban hub along with its surrounding areas. According to Aspeslagh (1994), a bioregion is a distinct area with coherent and interconnected human, plant and animal communities, and is defined by a watershed or a set of interlinking watersheds.

This bioregion is continuously replenishing the ecological demands of the urban hub, thus adding on to the overall urban carrying capacity. But with the prevailing scenario of urban development, these bioregions are getting sparse and sparse day by day. So, there is an urgent need to evaluate the urban carrying capacity by which a sustainable regime could be planned.

2.3. Levels of carrying capacity evaluation in an urban area

The evaluation of urban carrying capacity is a pretty complex process. This complexity is due to the fact that the capacity to support humans is determined not just by the basic food requirements, but also by the various kinds of resources consumed, the many kinds of wastes generated, different kinds of landuse conversions leading to ecological imbalance and the great variability in technology, institutions and lifestyles created. Aspeslagh (1994) defines six levels for evaluating carrying capacity of the urban areas. They are as follows:

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Fig 3: Diagram of a bioregion

WATER BODIES

URBANHUB

FOREST LAND SUB URBAN AREAS

AGRICULTURELANDS

BIOREGION© CoE ILPWRM


i. Infrastructural capacity level ii. Institutional capacity leveliii. Perceptual capacity leveliv. Environmental capacity levelv. Sustainable capacity levelvi. Biocentric capacity level

Infrastructure capacity level: At this capacity level, the major factor of evaluation is the infrastructure development. Here the intensity and pattern of resource usage is estimated for the development of infrastructure like, water supply system, sewage system, transportation system, waste disposal system, etc.

Institutional capacity level: The various legal and political frameworks that have been made to limit urban activities are considered here. The level of enforcement of various acts like Environment protection acts, Biodiversity conservations act, as well as zoning regulations, building permits, landuse ordinances, etc are assessed to evaluate the carrying capacity.

Perceptual carrying capacity: These constraints are generally perception based, i.e. they reflect the idea of a common man towards its environment. The way of assessment is social surveys whereby the basic thinking of people & their duties towards environment can be evaluated.

Environmental capacity level: This level basically reflects the present state of the environment with respect to productivity. One can easily understand the state of productivity of the environment, e.g. agricultural productivity by evaluating the past data. Another way of assessment is the availability of clean air & water, low pollution, etc.

Sustainable capacity level: The factors which are assessed at this level are long term based. The basic resource flow through the urban area to its ultimate sink is evaluated at this capacity level. Hence, an idea can be achieved corresponding to a particular resource as how long it will be available for usage. If a resource is getting scarce then efficient steps could be taken to sustain it for long.

Biocentric capacity level: This capacity level deal with ethics related to life on earth. At this level the different threats are assessed which harm the integrity, stability and beauty of the biotic community of an urban area. Unlike, the previous capacity levels that totally deal with human & its need, this capacity level embraces all forms of life as well as their requirements from the environment.


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2.4. Calculation of urban carrying capacity

Though it is evident that carrying capacity estimation serves to be one of the most crucial answers to the question of sustainable development and thus to the very survival of humankind, yet an irony remains. Carrying capacity is very difficult to estimate or calculate. Arrow et.al. (1995) comment that carrying capacity is not static but is based on the complex relation of preferences, application of technology and patterns of production & consumption. They are also contingent on the state of interactions of the biotic and abiotic environment. So the different workers have come up with various models which give an idea about calculation of carrying capacity:

i. Graphical modelii. Uni-constraint model

iii. IPAT equationiv. Ecological Footprint modelv. Energy analysis model

vi. Pressure-State-Response model

Graphical model :

This model is a graphical representation where the population growth is plotted against time. The population growth can be of two types, i.e. exponential and logistic. If there is no environmental resistance then the population growth trend is always exponential, which eventually leads to population explosion and ecological malfunctioning. The environmental resistance comes into play when the population exceeds the carrying capacity. Hence, due to the property of resilience the environment tends to stabilize. Thereby equilibrium is achieved in the population growth form, i.e. logistic growth form.Based on demographic data the urban carrying capacity can be calculated using this model.

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Fig 4: Graph showing the population growth forms

GRAPHICAL MODEL© CoE ILPWRM

Logistic growthdN/dt=rN{(K-N)/N}

Carrying capacity (K)

Exponential growth (dN/dT=rN)

Po

pu

lati

on

(N

)

Time (T)


Uni constraint model :

A “constraint” is an information key that tells us about the likelihood of limits. In this particular model a single constraint is considered and the entire estimation is based on the assumptions circling the considered constraint. The population constraints can be food, shelter, clothing etc. But one at a time can be considered in this model. As for example, if one considers the constraint of food, then the estimation of carrying capacity would involve the amount of available farmland, the average yield of crops, the prevalent diet, and the amount of calories to be provided to each person each day.

IPAT equation:

It is a multi constraint model that uses different factors in calculating the carrying capacity. This mathematical equation is one of the most pioneering attempts to estimate the level of environmental degradation by the dwelling population in an urban area that incorporates the usage of multiple factors or constraints.

I=P x A x T

Here, “I” refers to the Impact on the environment, “P” refers to the size of the human population, “A” refers to the affluence or the level of consumption by that population and “T” refers to the processes used to obtain resources and transform them into useful goods and wastes.

The IPAT equation, thus gives an idea about the cumulative or associated impacts of the population, its resource usage patterns and technological interventions on the environment. It does not give any information on the sustainable limits, i.e. optimum carrying capacity but it surely gives a useful framework in thinking about ways of reducing environmental impacts by reducing various types of throughput. Hence one gets an indirect approach of estimation of carrying capacity by understanding the level of environmental degradation.

Ecological Footprint model :

This is one of the most accepted models to calculate carrying capacity of an urban area. The model was developed by Mathis Wackernagel at the University of British Columbia, Canada as PhD dissertation (1990-94) under Prof. W.E.Rees. Initially they called the concept “appropriated carrying capacity”, which was later on termed as “ecological footprint” to make the concept more understandable and accessible. The ecological footprint is a measure of the human demands on the biosphere. This model gives an idea about the amount of biologically productive land and water area required to produce all the resources needed by the population for its consumption and developmental activities as well as to absorb the wastes generated.


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The Ecological Footprint model is based on the data generated from resource accounting. The different nations in the world are following a resource accounting plan whereby they have

categorized their total ecologically productive land into six areas. As such, six types of ecologically productive areas are distinguished in calculating the ecological footprint:

§ Arable land

§ Pasture

§ Forest

§ Ocean

§ Built-up land &

§ Fossil energy land

An ecologically productive area can be define as an area that produces the resources required by its dwelling population as well as absorbs the wastes generated by the same. Since, ecological

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Fig 5: Illustration of the ecological footprint concept

ECOLOGICAL FOOTPRINT MODEL© CoE ILPWRM


footprint and carrying capacity are both measured in the same units, they can be compared directly. If the ecological footprint of a region is larger than the carrying capacity, the region runs an “ecological deficit”. On the contrary, if the carrying capacity of a region is larger than the ecological footprint, the region runs an “ecological remainder”. At the end of the resource accounting survey for ecological footprint determination, the values are converted into a normalized measure of land area called “global hectares” (gha). According to the ecological footprint analysis done in the year 1997, the world average of ecologically productive land per person is 2 ha without considering the area required for reserved conservation lands. If we consider that then the figure comes to about 1.7 ha/person.

For 2005, humanity's total ecological footprint was estimated at 1.3 planet Earths, i.e. humanity uses ecological services 1.3 times as fast as earth can renew them. (

foot print).

The above graphical representation reveals the condition of 13 countries and the whole world with reference to their ecological footprints in 1997. USA was having a larger ecological footprint with respect to its available ecological capacity, i.e. it was facing an ecological deficit in the year 1997.

Http://en.wikipedia.org/ wiki/Ecological


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Fig 6: Graph showing the ecological footprints of different nations along with the available ecological capacity (from Campbell, 6th Ed.)

Copyright @ Pearson Education, Inc., Publishing as Benjamin Cummings


However, New Zealand was having an ecological remainder in the same year. Our country India was just at the threshold level in the same year.

Energy analysis model :

This model was developed by Odum. It is a quantitative measure of the resources required to develop a product, whether it is a mineral resource, a biological resource or a commercial product; and it expresses the resources in units of one type of energy, usually solar energy. It provides a bridge between ecological and economic systems. As a helpful tool for evaluating rational use of natural resources, it provides a system for quantifying facts for evaluating environmental resources (Zhao et.al. 2005)

Pressure-State-Response model :

The PSR model is a framework developed by the Organisation for Economic Co-operation and Development (OECD) that provides a mechanism to monitor the environment. It is basically a socio-economic concept that tends to investigate and analyze the processes involved in environmental degradation. This framework is based on the fact that human exert “pressure” on the environment by their activities which results in the radical change of the “state” of the environment. This changed environment state puts impacts on the human population in the form of some disasters that lead to the origin of “responses” which intend to prevent, reduce or mitigate the environmental and socio-economic damage. The PSR framework is based on some indicators that form an integral part of the whole analysis.

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Fig 7: Diagrammatic representation of the Pressure-State-Response model

© CoE ILPWRMIITG

CONSERVATIONPROTECTION, etc

LANDSLIDES,FLOOD, etc.DEFORESTATION,

POLLUTION, etc.

DEGRADATION OFTHE ENVIRONMENT

IMPACT (on people)

RESPONSE(by people)

STATE (of environment)

PRESSURE(on environment)

PSR MODEL


Chapter 3

“SAFE” CARRYING CAPACITY MODEL PROPOSED BY COE (ILPWRM) AT IIT GUWAHATI

3.1. Introduction

After reviewing all existing concepts and methods of evaluating carrying capacity, Center of Excellence (CoE) for Integrated Landuse Planning and Water Resources Management (ILPWRM) at IIT Guwahati has come up with a new method especially suitable for eco-sensitive urban areas. The method was first developed for calculating carrying capacity of hilly urban area that will ensure hazard free sustainable urban development. However the concept can be applied to any urban area. Here, the basic concept of ecological footprint is first used to decide a trial sustainable carrying capacity of a watershed or cluster of watersheds covering the urban area or expected urban area under consideration. Watershed boundary covering extent of potential urban expansion or the urban planning area is considered here as system boundary and interaction with bioregion can indirectly be included through concept of regional planning. Following this, a trial carrying capacity is first determined by allocating population and infrastructures iteratively, so that the infrastructures provided remain sufficient to cover the virtual footprint of the allocated population. Feedback of the urban watershed is then analyzed through model study after virtual accommodation of this trial carrying capacity in the model. Feedback can be assessed in terms of several case-specific performance criteria to ensure that the area remain hazard free. In case of inadequacy, technological intervention is first tried to make it adequate. After ensuring that state of the art technological intervention is also insufficient to meet the set performance criteria, the trial carrying capacity is adjusted iteratively to arrive at an acceptable carrying capacity by reducing floor area ratio (FAR), which also indirectly determines the actual and logical FAR for the urban area. For example performance criteria can be accepted limiting values for sediment yield and water yield from the urban watershed so that flooding at downstream can be eliminated. Putting these limits as constraints one can arrive at the acceptable carrying capacity iteratively by analyzing feedback of the urban watershed in terms of these performance criteria. As the method finally accommodates a sustainable population iteratively through trial allocation and feedback analysis, the method is named as “Sustainable Accommodation through Feedback Evaluation (SAFE)”


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3.2. Framework for calculation of carrying capacity using method of “Sustainable Accommodation through Feedback Evaluation (SAFE)”

To elaborate the steps involved in calculation of carrying capacity by the proposed “SAFE” method, step by step procedure is presented below with example of development of a hilly urban watershed.

Step 1: Delineation of the urban watershed: In this step the hilly watersheds covering the potential urban area are delineated from DEM or marked from the city master plan following natural drainage network.

Step 2: Demarcation of the developable & non-developable area: The hills consist of both developable areas & areas having less scope for development, i.e. non developable areas. In this step, the non-developable areas of the delineated hilly region are demarcated using latest geospatial tools. The non-developable areas mainly consist of land with high slope, reserved forest areas, water bodies, stream lines, drainage channels, springs, depressions, etc. Thus the usable areas with respect to various developmental activities can be marked out.

So, A = A +A ...……… (i)U D ND

Therefore, A = A - A ............. (ii)D U ND

Here, A is the total hilly urban area, A is the net developable area and A is the U D ND

net non developable area.

Step 3: Determination of area required for different infrastructure and facilities: Now within the developable regions of the hilly urban areas, several sub-regions are allotted for various urban infrastructure and facilities development like, water treatment plants, sewage treatment plants, drainage, commercial hubs, heath centers, educational institutions, recreational areas, transport facilities etc. For calculating these areas the regional planning approach is adopted as a tool. For example, an urban centre with a population of 1000 will not need a solid waste dumping site; rather a provision of solid waste dumping can be kept by tying with the regional dumping site. Space required for different infrastructure can be determined through site specific requirement. The standard space requirement index of the UDPFI guidelines of the Ministry of Urban Development, Government of India can also be used as a guideline for calculating the required space for various infrastructure developments.

So, A = A + A ................ (iii)D IF R

Here, A is the area for infrastructure development and A is the area for residential IF R

requirements.

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Step 4: Calculation of the available residential area: The net residential area available for settlement development can be calculated using the following equation:

From (i) & (iii) A = A + A + AU ND IF R

Therefore, A = A - (A + A )R U ND IF

Step 5: Socio economic survey of the urban region & calculation of the floor area requirement of the people: A thorough demographic and socio economic survey of the hilly urban area should be done to estimate an average floor area requirement per head of the people dwelling there. In this regard the national floor area standard values (MoUD, GOI) can be consulted to get an understanding of the same. The floor area requirement of the people will greatly vary with respect to economy and lifestyle of the people living there.

Step 6: Determination of the Floor Area Ratio: Floor Area Ration is defined as:

FAR= A /AF P

Where, FAR is the Floor Area Ratio, A is the total floor area and A is the area of the plot.F P

FAR need to be determined by considering various aspects like, provision of intended free space, safe bearing capacity of soil, economy of people for affording earthquake resilient structures, drainage and transportation requirement and so on. While the proposed “SAFE” method itself will determine an acceptable FAR, one need to provide an initial value of FAR. This value can be given from guidelines provided by different organization including ULB. In absence of any such guidelines, a value of 1.5 can be used for initial trial value. This value is suggested based on the general trend observed so far in Indian condition.

Step 7: Calculation of carrying capacity: Based on the overall study, the carrying capacity of the area with respect to urban development can be calculated using the following equation:

CC= A - (A + A ) x FAR/SU ND IF

Here, S is the Floor area requirement per head.

Based on the trend of population growth, the demands of the people with regards to infrastructure and other facilities will also increase. Hence, it is advisable that the carrying capacity should be periodically calculated using the above relation so as to check haphazard, unplanned or illegal development which will harm the ecosystem in the long run by calling hazards or natural calamities.


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Step 8: Check for adequacy of drainage system, sewerage system, water quality etc which were not explicitly considered during carrying capacity calculation. If inadequate, following two options need to be tried in sequence:

i. Apply possible Ecological Management Practice to bring sediment yield, peak discharge, sewerage volume and water quality within permissible limit

ii. Reevaluate the carrying capacity by reducing FAR

3.3 Application of the concept to practical field : A case study of a pilot watershed in Guwahati City of Assam, India

The study watershed is located near the Games village area of Guwahati City of Assam, India. The watershed has an area of 0.17sq.km. The process of delineation of the watershed is done initially by using ASTER DEM data in ArcSWAT and followed by refining of the selection using the drainage line of SoI toposheets.

The TIN model for the area is developed by using 20 m contour interval obtained from SoI toposheets (1:50000 scale). From the TIN, the slope and aspect map of the area was developed. The area is located within an elevation range of 11m to 200m. The slope ranges from 0 to 40%. The major soil type of this watershed is fine and coarse loamy type as obtained from soil map of Assam Remote Sensing Application Centre (ARSAC).

Figure 8, 9 and 10 shows the GIS based maps of the study area.

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Fig.8. The maps of the study site


Fig. 10. The demarcated watershed showing the developable & non developable areas

3.3.1 Computation of carrying capacity

A computer program developed for the purpose was used in order to produce an appropriate value of carrying capacity. This value can be called as the calculated carrying capacity. A socio economic survey is carried out in the area to understand the population status, land requirement, economic status, etc of the people residing there. The survey of the area has highlighted the absence of basic infrastructural amenities. Hence the following infrastructures are being considered for the area:


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Fig. 9. The slope map of the study site


l Water treatment plantl Sewage treatment plantl Park/ open areal Health facilityl Socio cultural facilityl Postal servicesl Milk booth l Transportationl Business/ commerce area

Based on primary and secondary data collected on required area for different infrastructure and also considering some minimum value for some of the infrastructures, logical statistical relationship between infrastructure and population were developed.

The following constraints are taken for demarcating the non developable area in the study area:

Stream buffer: 20 mSlope: > 30% with 5 m buffer

The FAR of the area has been taken to be 1.5 following Master Plan for Guwahati Metropolitan Area (GMDA, 2009). For example, if one decides to construct house by covering 50% of his land area, then he can go maximum up to 3 storey building. However acceptability or possible scope of enhancement of FAR=1.5 may be reviewed for hilly area from consideration of maximum permissible surcharge load from slope stability point of view.

The socio economic survey has shown that the people residing in the area are lower middle class. Requirement of area for different infrastructural facilities for the study area was determine by using standard norm. For the facilities, for which standard norms were not available, effort was made to develop logical relationship between population and desired infrastructural area based on data collected for such existing infrastructures in other areas. While using such relation care has been taken that for essential facilities a minimum area is assigned even if the population is quite low.

Based on analysis of socio-economic status of the present population and considering future possible matrix of different classes, an average logical floor area requirement is being considered at 0.002 ha per head. The overall analysis gives the calculated carrying capacity to be 782 persons. The results obtained regarding area of different infrastructure for this computed carrying capacity is given in the Table 1.One of the most distinct points which are being dramatically rendered unseen by the policy makers and developers is the ecological disturbance induced by the growing population leading to multiple hazards.

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The development of infrastructure and other facilities in hilly area generally cause land leveling and cutting of vegetation rendering open or barren land. As urban flood is a major problem for the study area, and enhanced sediment yield and water yield adversely affect the flooding scenario, these two factors have been taken as the performance criteria to assess feedback of the watershed after accommodation of the calculated carrying capacity. In the present study the total built up area requirement is projected to be 5.7ha resulting into an additional barren land output of 1.8ha. The sediment and water yield scenario of the watershed is estimated by using the RUSLE method and Rational method which is presented in the given in Table 2: Table-2 shows that both the values cross the permissible limits. As per the procedure of SAFE model, technical intervention was first attempted by applying ecological management practices or simply EMPs, which nullify the dwindling ecological status.

Area of the watershed 17ha

Non developable area 8.4 ha

FAR 1.5

S 0.002 ha

Infrastructure Total area obtained (ha) Coverage (%)

Water treatment plant 1.076 60

Sewage treatment plant 1.076 60

Health 0.010 60

Parks 0.478 20

Socio cultural facility 0.010 20

Postal service 0.004 60

Milk booth 0.004 60

Transportation with road side drain 1.700 100

Business & commerce 2.550 80

Open space 1.700 0

Total infrastructural area 7.558

Total residential area 1.042

Total cover area 5.7

CALCULATED CARRYING 782CAPACITY(Person)

Table1: Calculation of land requirement for infrastructural facilities


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Table 2: Calculation of sediment and water yield

The projections derived after analyzing the models considering the estimated carrying capacity direct towards a higher runoff and sediment yield when compared to natural or undisturbed areas. Taking into consideration the ever increasing development regime of the nation it becomes really difficult to control the runoff and sediment without management practice. Moreover it is not desired to lower the population. So an optimization model was developed to decide most economical and feasible combination of EMPs to reduce sediment and water yield in an ecologically sustainable way. In this regard an analysis is done using the OPTEMP-LS (OPTimal EMP model with linear programming for a watershed having Single ownership) model developed for the purpose to estimate the effectiveness of the EMPs in reducing the runoff and sediment yield. Based on the value of sediment and water yield in natural condition and also considering the drainage capacity of downstream the sediment yield and peak discharge should lie in the range of 0-2000 tonnes/yr and 0.5-1.5 cumec respectively.

Considering the economic status of the people, location of the plot and factor of cost effectiveness, the EMPs like grass cover, garden (with ornamental or fruit plants) and detention pond (with fishery, boating facility etc) are being considered. By employing these EMPs the following benefits can be achieved:

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Sediment yield of

watershed(Using the

RUSLE method)

Water yield of the watershed

(Using the Rational Method)

Natural (without build

up area)(Tonnes/yr)

Disturbed(considering the

calculated carrying capacity)

(Tonnes/yr)

Natural (without build up area) Peak flow (cumec)

Disturbed(considering the

calculated carrying capacity)(cumec)

2117

0.48

6774

2.04


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l The vegetative cover over the land will lower sediment yield and run off. Thus minimizes the chances of flood and landslide hazards.

l The people can get monetary benefits from the fruit gardens and fishery thus enhances their economic status.

l The aesthetic beauty of the plot is increased which will enhance the scope of eco-tourism.

After implementing the desired EMPs in the optimization model the following results are obtained [Table 3 and Table 4]:

Table 3: Results of the EMP optimization model

0.2 0.623 0.05

Table 4 : Peak discharge, sediment yield and optimal cost of EMPs considering the EMPs in the study site

0.73 2000 2679222

The results of the optimization model clearly reflect the feasibility of EMPs from economic and ecological point of view. It can thus be readily advised to allow the population up to the calculated carrying capacity (782 nos.) and to develop the hilly area by employing EMPs to control the hazards and conserve the ecosystem forever.

Grass Garden Detention pond(Area in ha) (with fruit and (with fishery, boating

Ornamental plants) facilities etc) (Area in ha) (Area in ha)

Peak discharge Sediment yield Optional cost (with EMPs) (with EMPs) for the EMPs (cumec) (tonnes/yr) ( )

l

l

l

http://censusindia.gov.in/Data_Products/Library/Indian_perceptive_link/Census_Terms_link/censusterms.htmlhttp://censusindia.gov.in/Data_Products/Library/Indian_perceptive_link/Census_Terms_link/censusterms.htmlhttp://www.iucn.org/programme

REFERENCES

l Oh K., Jeong Y., Lee D., Lee W. and Choic J. (2005). “Determining Development Density using the urban carrying capacity assessment system”, Landscape and urban planning, 73, 1-15.

l Rees W. (1992). “Ecological footprints and appropriated carrying capacity: What Urban economics leaves out”, Environment and urbanization, 4,121.

l Zhao S., Li Z. and Li W. (2005). “A modified method of ecological footprint calculation and its application”, Ecological Modeling, 185, 65-75.

l Lane M. (2009). “The Carrying Capacity Imperative: Assessing Regional Carrying Capacity Methodologies for Sustainable Land-Use Planning”, Proceedings of the 53th Annual Meeting of the International Society for the Systems Sciences, 1-20.

l Ewing B., Goldfinger S., Wackernagel M., Stechbart M., Rizk S., Reed A., Kitzes J.,(2008) “Ecological foot print atlas” .Global Footprint Network, 1-87.

l Arrow K., Bolin B., Costanza R., Dasgupta P., Folke C., Holling C.S., Jansson B.O., Levin S., Mäler K.G., Perrings C., Pimental D., (1995) “Economic Growth, Carrying capacity and the environment, Science, 268, 1-2.

l Aspeslagh W., (1994) “Carrying Capacity and its application to Portland metropolitan area” Discussion paper, 1-90.

l

l

l

http://en.wikipedia.org/wiki/Ecological footprinthttp://smallstock.info/issues/psr.htmhttp://corbettcares.com/sustainability/eco-footprint/

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Documents

ˇˆ˙˝˛ ˝ˆˆ˚ - Indian Institute of Technology Guwahati Carrying Capacity.pdf · 1.3. Significance of c arrying cap acity The w orld is dev eloping by le aps and bounds. Dev