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"CITY GREEN PLAN" as a means to achieve sustainable development - GIS APPROACH


Ar. A. Meenatchi Sundaram
Teaching/Research Associate, SAP, Anna University,
Chennai, Tamil Nadu.
minchu50@hotmail.com

Abstract
Vegetations playing an effective roll in the urban environment (ecosystem), supporting many fundamental sub systems like hydrological cycles, Nutrients cycles, atmospheric gas balance etc. However increasing population and the burgeoning urbanization process are converting more and more soft green spaces into impermeable hard concrete surfaces. Man’s implication of this activity derelict the green spaces, and put his city in a deprived state of “GREENS SERVICES”. Hence the urban areas experiencing water scarcity, air pollution, heat islands etc., apart from many such problems. Number of such studies under taken in this direction suggesting that, the development of green areas will improve the present urban environmental conditions.

There are number of attempts in this direction to increase the green spaces in the urban areas such as, urban forestry, Silviculture, Afforestation, Social forestry etc., with the aim of improving the environmental condition. It is absorbed that the number of such activity does bring more green spaces, however attempts on the integration of trees, as an element of urban landscape are missing. Such an attempt would deliver functionally more effective and aesthetically pleasing environment. This requires many data / parameters such as ownerships, soil types, hydrology, topography, micro and macro climatic aspects, size and nature of the city etc. Provided all this data with the tool like GIS, it is easy to develop an effective proposal of “CITY’S GREEN “, to address environmental and aesthetic issues of urban area.

This study is an attempt in this direction tries to evolve an effective methodology using GIS as a tool, to integrate, this environmentally important element, as an effective functional element of the urban landscape.

Introduction
The forces and processes of technological development, globalization and population growth accelerate the dynamics of urbanization process in the developing country. This could be visualized by the percentage of people living in the urban area has been increased from 14% to 45% between the year 1900 to 1993, and it is expected to increase to about 61% by the year 2025 among the total world population (1). Number of cities also increase, as there were only 83 cities in 1950 with a population of more then one million and 34 of them in the developing country, and today there are around 280 of such a settlement in the world and expected to double by the year 2015.Roughly 150,000 people are added to the urban population of developing countries every day. (2)



This trend is also holds good for mega cities (defined as a city with a population exceeding 8 million). There were only two in 1950 (New York, with a population of 12.3 million, and London, with 8.7 million). By 1990, there were 21 mega cities, 16 of them in the developing world. In the year 2015, there will be 33 mega cities, 27 in the developing world (WRI-96). Thus, the ever increasing, urbanization process are constantly escalating the socio-economic demands, which altering the biophysical environment of the city. Hence the city becomes less natural / livable with lots of environmental problems, cumulatively it changed the global environment system.(27)



Urbanization Vs. Environment
This rapid growth rates of many cities, combined with their huge population base, are pushing the cities to unprecedented sizes, These processes modified the natural features of a city and its surroundings (geography, topography, and climate), through three main ways: 1.The conversion of land to urban uses, 2.The extraction and depletion of natural resources, and 3.The disposal of wastes in the urban area. As the cities expand, through conurbation process, prime agricultural land and habitats such as wetlands and forests (in and around the city) are transformed into land for housing, roads, industry, etc.(21). The increasing numbers of research by the environmental scientists, have the common opinion that the fundamental capacity of the natural capital (biophysical component) to support the humanity on this earth itself reached the threshold (Daly and cobb, 1989,Janson et al 1994), because of the rapid conversion of the biophysical elements in the urbanization process.

For example:

• In US, the total amount of land under urban uses increased from 21 million hectares in 1982 to 26 million hectares in 1992. In one decade, 2,085,945 hectares of forestland, 1,525,314 hectares of cultivated cropland, 943,598 hectares of pastureland, and 774,029 hectares of rangeland were converted to urban uses (3).
• Five percent of China’s total croplands were lost within six years (1986 – 1992), because of urban expansion and industrialization (web 1).
• During the year 1972 – 1983 open space in the major Indian cities are depleted around 50%.(4) (Table 2.1)

It is expected that in the year 2025,the population of the earth will reach 8 billion, in that 5 billion will be the urban population, and nearly 476,000 hectares of arable land in the developing countries is being transformed annually to urban uses (WRI).



As the result, the urban areas experiencing many environmental problems like air pollution, depletion of the ground water table, water scarcity, microclimatic change, flooding and soil erosion, more variation in the diurnal temperatures etc.

For example:

• Since 1965, the water table fallen by some 59m or nearly 200 feet due to continues extraction of water to meet the growing urban population need (W.W.I). The Yellow river, cradle of China, after flowing uninterruptedly for thousand of years, failing to reach the sea from 1972 onwards as a result of reducing the green, part of urbanization process along the banks of the river (6)
• As the result of over extraction of the ground water, Bangkok metropolitan sank 1.6m (63inch) during 1960-1988 (3).
• The estimation of National flood commission of India shows that the flood prone area increased from about 40 million hectares in 1978 to 59 million hectares in 1987. (6).
• During 1950-1970, around 400,000 km of green space in the core of the Sao Paulo city (Brazil) was converted to urban use, as the result the city’s temperature increased by 10 deg. more than outskirts. (3)

(Note: WRI- World Resource Institute, WWI – World Watch Institute)>