Vinay Kumar Srvastava
Assistant Professor of Geophysics
Indian School of Mines, Dhanbad
Integration of remote sensing and geographic information system (GIS) provides a mean to update theme oriented informations and mapping of dynamic features of earth surface for better management and planning. Using this characteristics an attempt has been made to study urban sprawl since 1974 till 1990 in an around Jharia Coalfield (Dhanbad) where coal is being exploited for the last hundred years. The results have shown that the rate of urban growth around 4% per year in the region leading to almost 60% increse in area during the last 16 years. Urban sprawl has basically taken place on surrounding agricultural and flat upland but not on derelict land generated by the mining operations. Such developments have spoiled the aesthetic of land and physical environment in general.
Rapid industralisation causes haphazard and unplanned growth of urban centres which becomes more complicated but the fact that it must take place within the built up area. This pressure of continuously growing population results in over crowding and become brurden to limited civic cycle amenities which forces the middle class as well as builders to move to outlying suburbs, a phenomenon called Urban Sprawl or Growth.
This irregular growth of urban area consumes agricultural and flat upland on their periphery. Such urban development ultimately snowball into a liability when they become part of the city as far as infrastructural facilities are concerned. Therefore proper planning has to be done for controlled and regulatory growth of urban centres. Basic requirements for such planning outdated. They required to be updated and revised. But updating of existing map by conventional means takes much time and also by the time it is made available to planner, it lack real time information’s.
At this point remote sensing techniques which gathers data about earth’s surface features in raster form on a periodic basis and geographic information system (G. I. S.) which helps in analysis and integration of relational data base containing both spatial and aspatial details through automated machine processing system provides and alternative means for the mapping of dynamic features on regular intervals. By such integrated study it is possible to take relevant decisions at the appropriate time by the urban planners (Shelton & Estes. 1981).
Walsh et. At (1990) have shown that the thematic overlays contained within GIS could be used as reference sources for defining the spatial location of phenomenon and also for comparing such phenomenon against identified features employing digital processing of remote sensing images and selected thematic overlays integrated with in GIS, where digital enhancements are apprised with greater capability then by use of remote sensing for GIS alone.
The general methodology followed for integration is to convert remote sensing data into a geometrically corrected thematic map on grid square elements of GIS or alternatively integrated with other data elements of G. I. S. Conecpts of both the techniques are shown in block diagramme ‘la’ and ‘lb’ respectively (after curran (1985)).
Finally once a theme oriented GIS is created it becomes easier to study the process of planning and management of land by (i) indicating how changes and improvement in the existing situation can be achieved, (ii) Considering what effects can be expected as consequence of the change envisaged.
In the present study techniques of remote sensing and GIS have been applied in monitoring of urban growth since 1975 in and around famous Jharia Coalfield covering an area of 720 Sq. Km. of Dhanbad District (India), using methodology as shown in ‘la’ block diagram. The thematic maps obtained from processed remote sensing imagery have been compared with available maps and integrated and analysed in reference to database of 1974 for delineating change status till 1990.Description of the Study Area
The study area Jharia Coalfield as shown in fig.1 is the only source of prime coking coal in India and has been subjected to unplanned and haphazard mining activities for the last several decades. This belt which forms part of Damodar Valley coal basins is surrounded and directly underlained by archaean gnesis. Exposed rock types belong to talchir and Damuda series of Gondwana Sytem. This Damuda series of Gondwana System. This Damuda series consists of Barakar, Barren measure and Raniganj formations contain famous coal seams. The general landscapes of the area is characterised by undulatory rocky and gritty surface with thin veneer of insitu soil supporting thin and spoadic vegetation.
With the increase in petrol price, coal being the other important source of energy the coal exploration in the region increased manifold during the last 2-3 decades. This increase in mining industry and related growth of ancillary industries in the region particularly after the nationalisation of coal mining since 1971 has caused sudden influx of large human population from surrounding region. This has resulted in high growth of human settlement in the region but in irregular manner adequate civic amenities. This has led to over all degradation of environment and uneven development of all settlement. The area look desolate with dominance of disarranged mining, quarries wastelump, subsidence, scattered settlement etc.
Data and Methodology
The remote sensing images of Landsat-TM acquired Aug. 1990 have been used for present study. The digital data were processed for geometric and radimetric corrections using VGA-ERDASimage processing software. Later a standard false color -composite image was generated using Landsat TM band 2.3 and 4 (visible and near infrared images). This image was filmed and was enlarged to 1:50,000 working scale using PROCOM-2, a high magnification device.
This color image was then interpreted using standard photo-interpretration technique based on shape, size & color for delineating urban boundary. In F.C.C. urban area is associated with bluish grey to mottled grey color tone due to presence of plantation and bushes in and around the built up area. Then the aerial extent of the identified urban areas were checked in field at critical spot for overall improvement in mapping accuracy.
The status of urban area for the year 1974 was traced from the Survey of India toposheets covered by 73 I/5, 73/I6, 73 I/2, 73 I/1 in 1:50,000 scale.
This traced boundary was then superimposed on map of 1990 prepared from remote sensing images and then a changed status map was drawn.
Results and Discussions
Urban sprawl and changes in status of urban areas /centres from 1974 to 1990 in the region is shown in fig.2. This clearly shows a big increase is around 60% i.e. 290 Sq.Km. in total study area of 720Sq. Km. of Jharia Coalfield. This has given a growth rate of 4% per year which is much faster than compared previous 60 to 70 years of mining history in the region, Srivastava (1991).
This is probably due to fact that the status of 1974 represents the scenario just prior to nationalisation of coal mining industry and till then the operating mining companies, and local people were not concern about the housing and proper growth of the township. The urban areas grew only in and around of working sites and so no significant urban sprawl was observed in the previous periods. But during 16 years of nationalisation township were developed away from the over crowded old urban areas particularly for providing clear environment of living. So a high urban growth rate was observed during this period.
Many new centres of urban growth came up oin addition to increase in dimension of earlier settlement centres. However agglomerates of built up areas were seen more in the eastern part of the study area than in other part. Significnt growth occurred in and around Dhanbad in the north east, Karas in the north, Jharia in the east and Baghmare, Mahuda, Bokaro in the west.
It is further observed that the urban sprawl has consumed surrounding agricultural and flat upland but leaving the derelict land on rural-urban fringe has not only spoil the aesthetic value of landscape but has also hindered the further development of this region. This unplanned growth has altered the terrain and slope characteristics of the area causing change in surface drainage system and indirectly affecting geohydrology of the region. The change in geohydrological environment has badly affected the greenery in the region both in respect of quality and lessening of vegetation cover in Jharia Coalfield.
From present study through Landsat-TM F.C.C. image in combination with Survey of India topo sheet and other available maps it has been possible to delineate macro level changes in urban area on regional scale. Study has also shown that the urban the urban growth which is around 4% per year has been haphazard and irregular during the last 16 years i.e. since 1974. The growth has been basically taken place on surrounding agricultural and flat Upland leaving derelict land due to mining and waste dump region as isolated patches in between settlement centres. Such development has changed the terrain and slope characteristics of the region and hence affected the surface drainage system as well as water infilteration ratio causing depletion of ground water region. This changes in drainage and ground water level have resulted in lose and in the region. These factors have caused general degradation in the environment of the region.
Finally the study has demonstrated the importance of integrated study satellite remote sensing images in conjunction with other geographic maps and GIS data base. The technique is cost effective faster compared to conventional method of urban data acquisition and survey methods.
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