Significance of Morphometry Studies, Soil Characteristics, Erosion Phenomena and Landform Processes Using Remote Sensing and GIS for Kodaikanal Hills, A Global Biodiversity Hotpot in Western Ghats, Dindigul District, Tamil Nadu, South India
M. Bagyaraj and B. Gurugnanam
GIT Lab, Department of Earth Sciences, Annamalai University,
Annamalai Nagar-608 002, Tamil Nadu, India
Corresponding Author: B. Gurugnanam, GIT Lab, Department of Earth Sciences, Annamalai University, Annamalai Nagar-608 002, Tamil Nadu, India
Research Journal of Environmental and Earth Sciences 3(3): 221-233, 2011
Abstract:
An attempt is made to study the significance of morphometry, integrating Remote Sensing data and techniques in addition to the conventional methods in a GIS platform. The Western Ghats are amongst the eighteen biodiversity hot-spots recognized globally (WCMC, 1992) and are known for their high levels of endemism. Kodaikkanal Hills are parts of Palani hills of Western Ghats. The study has demonstrated the potential use of remotely sensed data and Geographical Information Systems (GIS) in evaluation of linear, relief and areal morphometric parameters and to analyze their influence on the genesis and processes of landforms and characteristics of soil parameters like texture, drainage and land erosion conditions. Visual interpretation of satellite data in analysis of geological, landforms and land erosion characteristics in conjunction with drainage pattern facilitates effective delineation of distinct features to evaluate the influence of drainage morphometry. GIS is an effective tool to analyze spatial and non-spatial data on drainage, geology, landforms and soil parameters to understand their inter-relationships. Geo-coded resource database generated on drainage, landforms and soil parameters in the core of GIS provides an excellent means of storing, retrieving and analyzing data at river basin level to find out their association. It also provides a powerful mechanism not only to upgrade and monitor morphometric parameters but also to permit the spatial analysis of other associated resources database. An attempt has been made to utilize the interpretation capabilities of GIS to find out the relationships between the morphometric parameters at sub basin level.
Key words: Bio diversity hotspots, GIS, land form, morphometry, relief, remote sensing, slope
INTRODUCTION
Morphometric studies involve evaluation of streams through the measurement of various stream properties. analysis of various drainage parameters namely ordering of the various streams and measurement of area of basin, perimeter of basin, length of drainage channels, drainage density (Dd), drainage frequency, bifurcation ratio (Rb), texture ratio (T) and circulatory ratio (Rc) (Kumar et al., 2000). GIS and image processing techniques have been adopted for the identification of morphological features and analyzing their properties of the Lower Gostani River Basin (LGRB) area in Andhra Pradesh state, India (Nageswarara Rao, 2010). River basins comprise a distinct morphologic region and have special relevance to drainage pattern and geomorphology (Doornkamp and Cuchlaine, 1971; Strahler, 1957). Horton’s law of stream lengths suggests a geometric relationship between the number of stream segments in successive stream orders and landforms (Horton, 1945). Quantitative description of the basin morphometry also requires the characterization of linear and areal features, gradient of channel network and contributing ground slopes of the drainage basin. Detailed analysis of drainage parameters is of great help in understanding the influence of drainage morphometry on landforms and their characteristics. The Western Ghats are amongst the eighteen biodiversity hot-spots recognized globally and are known for their high levels of endemism (Selvaraj, 2002). The study complements the efforts to understand the inter-relationship of various factors for planning, biodiversity management and disaster prone area zonation.
As compared to the conventional morphometry studies, using Remote Sensing enables extant ground reality inputs to assess changes in drainage patterns, density soil characteristics, Landuse changes and landforms present in real time.
In this context High Spatial Resolution Indian Remote Sensing Satellite (IRS)-P6 Linear Image Self Scanning (LISS)-4 sensor data of 7 July 2002, Survey of India (SOI) topographical sheets (1:50,000 scale) and field verification data were used for systematic analysis of various Geomorphic processes, hydrological and landform characteristics of the study area. Drainage Network analysis was carried out at basin level using Spatial Analysis GIS System (ArcGIS. 9.3) to identify the influence of drainage morphometry on landforms, drainage, and land erosion characteristics. The study demonstrates the fact that integrated Remote Sensing and GIS based approach is more appropriate and useful than conventional methods. The study seeks to utilize the interpretation capabilities of GIS to find out the relationships between the morphometric parameters at sub basin level on one hand and landforms, soil physical and eroded land characteristics on the other hand. The study complements the efforts to understand the interrelationship of various interacting factors for planning, biodiversity management and disaster prone area zonation.
Fig. 1: Study area
Study area (Fig. 1) Kodaikanal hills is located in the Dindigul district of Tamil Nadu with an area of 1039.46 km2 . It is geographically located between 77º14!26" and 77º45!28" E longitudes and 10º6!25" and 10º26!54" N latitudes. In the survey of India toposheet, it forms part of 58 F/7, 8, 11 and 12 on 1:50,000 scale. It is a part of the Western Ghats which is designated as one of the eighteen Biodiversity hotspots of the world. As a biodiversity hotspot it has variety of endemic flora and fauna. Its richness of epiphytes, orchids and thirteen different varieties of Shola forests are unique. Species accorded highly endangered status such as Nigligi Tahr (a mountain goat and the state animal are endemic to the region), Also the Shola forests serve as traditional Aniaml corridors for Bison, deer, elephants and the tiger. By virtue of sheer antiquity and virtual non regeneration they are termed as ‘living fossils’. Sunlight can not sufficiently penetrate the canopy and the accumulated litter and high alleochemical presence seeds can not let seeds to germinate. Loss of these unique systems is permanent and irreplaceable. They also remain as the watershed region of Vaigai, Manjalar Rivers catering to southern districts of Tamil Nadu. Destruction of these forests will amount to extinction of a vast array of plants and animals. Conservation efforts have to be interdisciplinary in nature and this study is one such attempt. The study area is anthropologically significant in that it is inhabited from prehistoric period and still there are tribals living in their ancient way.
On a tourism perspective the region is widely hailed as the ‘Princess of Hill Stations’ owing to the popularity it gained during British Raj. The climatic condition of the study area is characterized by humid conditions. Relative humidity is high during retreating NE monsoon season (October to mid December). The mean temperature of Kodaikanal taluk is 15.93ºC with a mean summer temperature of 17.29ºC (June, July and August) and mean winter (December, January and February) temperature of 14.10ºC. The average annual rainfall is 1436.87mm. The study area is fully covered by hills. The plain area forms a small part. The hilly area is in the form of undulating terrain and slope towards south-southeast and east. The maximum elevation is 2517 m, located in the south west portion. Labour intensive tea and coffee plantations and extensive vegetable cultivation mark the place. The settlements are created on the man made terraces and are densely populated in isolated pockets. Hence drainage patterns are intensely modified increasing the risk of landslide hazards.
Surface drainage characteristics of many river basins and sub basins in different parts of the globe have been studied using conventional methods (Horton, 1945; Strahler, 1952, 1957, 1964; Morisawa, 1959; Leopold and Miller, 1956; Krishnamurthy et al., 1996).
The aim of the study was to demonstrate the potential use of remotely sensed data and Geographical Information Systems (GIS) in evaluation of linear, relief and areal morphometric parameters and to analyze their influence on the genesis and processes of landforms and characteristics of soil parameters like texture, drainage and land erosion conditions. Visual interpretation of satellite data in analysis of geological, landforms and land erosion characteristics in conjunction with drainage pattern facilitates effective delineation of distinct features to evaluate the influence of drainage morphometry on landform characteristics and their processes. The high spatial resolution remotely sensed data coupled with topographical data analysis procedures have made satellite sensor data based morphometric analysis is a highly effective tool to understand and manage the natural resources (Srinivasan, 1988). It provides the real time and accurate information related to distinct geological formations, landforms and helps in identification of drainage channels, which are altered by natural forces or anthropogenic activities. Multispectral satellite sensor data provides a convenient means to analyze drainage and distinct landform characteristics at various scales. GIS is an effective tool to analyze spatial and non-spatial data on drainage, geology, landforms and soil parameters to understand their inter-relationships. Geo-coded resource database generated on drainage, landforms and soil parameters in the core of GIS provides an excellent means of storing, retrieving and analyzing data at river basin level to find out their association. It also provides a powerful mechanism not only to upgrade and monitor morphometric parameters but also to permit the spatial analysis of other associated resources database (Jain et al., 1995). Integration of remotely sensed data and GIS thereby provides an efficient way in analysis of morphometric parameters and landform characteristics for resource evaluation, analysis and management. An attempt has been made to utilize the interpretative techniques of GIS to find out the relationships between the morphometric parameters at sub basin level on the one hand and landforms, soil physical and eroded lands characteristics on the other hand.
METHODOLOGY
The Indian Remote Sensing (IRS)-P6 Satellite Linear Image Self Scanning (LISS) - 4 sensor data of 7 March 2002 were collected and registered to Survey of India (SOI) topographical sheets at 1:50,000 scale in the ERDAS image analysis system version. 9.3. The Kodai hills of Dindigul district was delineated based on the water divide line concept. The drainage network of the basin was traced on transparency and digitized as available on toposheets (1:50,000) and some of the first order steams were updated with the help of satellite sensor data. The elevation model was generated based on the contour values of 500 m interval to generate height and slope maps. The basin was divided into 48 sub basins and morphometric analysis was carried out at sub basin level in the Spatial Analysis GIS System (ArcGIS version. 9.3) methodology flow chart (Fig. 2). Some areas have been left out in the process of delineation of sub basins and were considered as unclassified. Based on the drainage order, the drainage channels were classified into different orders (Strahler, 1964). In GIS, drainage channel segments were ordered numerically as order number 1 from a stream’s headwaters to a point down stream. The stream segment that results from the joining of two first order streams was assigned order 2. Two second order streams formed a third order stream and so on. The sub basin area, perimeter, cumulative length of streams and basin length were measured in GIS and are expressed as A, P, L and Lb respectively. Parameters such as ruggedness number (Rn), drainage density, bifurcation ratio, stream frequency (Fu), texture ratio, form factor (Rf), circulatory ratio (Rc), elongation ratio (Re) and constant of channel maintenance (C) were evaluated with established mathematical equations (Strahler, 1964) (Table 1). The Study was contacted for parts of Kodai hills of Dindigul district. Base information is extracted from toposheets. Satellite data (2002) was used to extract landform characteristics. The study carried out in the year 2010.
The evaluated morphometric parameters were grouped as linear, relief and areal parameters. Visual interpretation techniques were followed for delineation of geology, landforms, and soil boundaries and degraded lands based on the tone, texture, shape, drainage pattern, color and differential erosion characteristics of the satellite imagery in conjunction with drainage morphometry and collateral data. Subsequently detailed landform analysis has been carried out based on their genesis, relief and their morphometric characteristics.
RESULTS AND DISCUSSION
Elevation: The elevation of the study area reveals that higher elevation of 2517 m above mean sea level is associated with dissected hills and escarpments in the south west portion of the study area (Fig. 3). The elevation ranging from 2000-2500 m above MSL is mainly confined to Hill top plains/Dissected plateau and structural hill. The elevation ranging from 0 to 500 m above MSL is mainly associated with lower parts of foot slopes, structural hill and pediments.
Fig. 2: Methodology flow chart
Table 1: Morphometric parameters and their mathematical expressions
CONCLUSION
The study reveals that remotely sensed data and GIS based approach in evaluation of drainage morphometric parameters and their influence on landforms, soils and eroded land characteristics at river basin level is more appropriate than the conventional methods. Interpretation of multi-spectral satellite sensor data is of great help in analysis of drainage parameters and delineation of distinct geological and landform units and eroded lands. GIS based approach facilitates analyzis of different morphometric parameters and to explore the relationship between the drainage morphometry and properties of landforms, soils and eroded lands. Different landforms were identified in the basin based on visual interpretation of satellite sensor data. These are dissected plateau, structural hill, structural valley and valley fill. The sub basin 4, 5, 26, 31 and 35 and are associated with high Drainage density (Dd), impermeable geology and high runoff conditions. High drainage density, high bifurcation ratio (Rb) and steep slopes are the main causative factors for the development of well drained soils. The soil drainage of the basin is associated with drainage morphometry and the majority of the area is under welldrained condition. Low and moderate eroded lands are noticed in the sub basins of 1, 2, 5, 15 and 16, which are in association with high drainage density, stream frequency and texture ratio. The detailed quantitative morphometric analysis at the sub basin level enables to understand the relationships among the different aspects of the drainage patterns and their influence on landform processes, drainage, and land erosion properties. The results reveal that the types of morphometry, underlying geology and slope factors have great influence on the gneiss and processes of the landforms. The derived morphometric parameters of the study area are closely following with the values obtained in similar terrain conditions (Subramanian and Subramanyan, 1978). The morphometric parameters evaluated using GIS helped to understand various terrain parameters such as nature of the bedrock, infiltration capacity, runoff, etc. Similar studies in conjunction with high resolution satellite data help in better understanding the landforms and their processes and drainage pattern demarcations for basin area planning and management.
Conservation efforts should take into account the importance of a Biodiversity hot spot and an interdisciplinary approach can pave way for sustainable development and ecolo gical preservation. This study is one such attempt.
ACKNOWLEDGEMENT
The Authors are thankful to UGC Division, Government of India, for the financial support to execute the present research study.
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