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Remote Sensing Techniques for Land Use Mapping of Arjuna Basin, Tamil Nadu
Methodology
The study has made use of various primary and secondary data. The Indian Remote Sensing Satellite (IRS) and Landsat satellite data were visually interpreted for the study of geomorphology and land use. The interpretation is carried out on 1: 50,000 scale using the image interpretation elements such as tone, texture, shape, pattern, association etc., Adequate field checks were made before ascertaining / finalization of the thematic maps.
Results and discussion
Analysis of Land use features by Remote Sensing Data
The various land use categories were identified and demarcated (Fig 2). Using IRS – IB LISS II Geocoded and Landsat TM data based on the image interpretation elements. They are described as below.
Built – up land
The built-up lands are areas of human habitation developed due to non-agricultural uses like building, transport, communication, and utilities in association with water, vegetation and vacant lands. These features can be identified with their dark bluish green tone in the core and bluish tone on the periphery. They have a typical coarse and molted texture. These areas are also associated with the network of canals, roads, and railway lines. Apart from the settlement, transportation lines were also identified with their typical straight, sharp and smooth curves.
In the study area, three major settlements are distributed randomly, two of which (Srivilliputhur, Sattur) are found in the southern part and the other in the east (Virundhunager). Few smaller settlements, which represent the minor towns were also mapped and this include Watrap, Peraiyur, Kallupatti, Tiruthangal and others.
The total area covered by the major and minor settlements in the basin constitutes 21.07 and 52.75 sq.km. 4.73% respectively.
Agricultural land
These are the lands primarily used for farming and for production of food, fiber, and other commercial and horticultural crops. By the help of satellite data, it is possible to identify the various agricultural lands upto level III. The information about the kharif, rabi and double cropped areas were identified with the help of multi date satellite data. The various categories of the agricultural lands identified in the study area are described in detail.
- Crop land
These include all the agricultural areas and these could be identified by their characteristic red tone, regular shape of the agricultural fields, association with the water bodies, etc., The crop lands are found well distributed throughout the foot hill zones and plain regions of the study area. By using satellite data of different seasons it was possible to identify the kharif, rabi and double cropped areas. The kharif crops (paddy, groundnut) are cultivated in the months or June, July and August. In the study are, such cropped areas were found mostly in the northwestern portions. The water availability from the nearby higher altitude areas facilitate the cultivation of these crops in these parts. It is interesting to note that such crops are totally absent in the south and the southeastern portions of the study area. Such cropped areas cover approximately 114.90 sq.km. The rabi crops mostly paddy, cholam, cumbu and maize are cultivated during the months of October, November and December. The crops cultivated during this season are found distributed all over the study area and it occupies 220.36 sq.km.
In certain areas, the crops are found to be cultivated in both the kharif and rabi season. The crops include paddy and groundnut. Such areas are categorized under double-cropped areas. These areas are found nearer the tanks, canals and along the rivers and streams and they occupy 136.89 sq.km. (6.81%).
- Fallow land
These are the lands, which remain vacant without crop during both the khrif and rabi seasons. These were identified by their dark greenish tone, smaller size, regular shape and medium texture. In the study area, such fallow lands are to be found well distributed in the central and southeastern portions. In the other areas these are to be found sparsely scattered. These occupy 395.84 sq. km. (23.46%).
- Plantations
These include areas where crops such as plam trees, coconut, banana, etc. Such areas were identified form their dark red tone, smooth texture and association with foothill areas, etc., In the study area, such plantations are found in the areas between Thaniparai and Watrap, areas along the Periayar, Chittar and Kovilar Rivers, which lie in the western portion of the study area. Approximately the plantation-cropped areas occupy about 29 sq. km. (1.72%).
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