Indian Journal of Geo-Marine Sciences Vol. 44(11), November 2015, pp. 1734-1741 Assessment of Environmentally Sensitive Area and Desertification Severity using GIS for an Indian Region - Virudhunagar District, Tamil Nadu *K.Vani, M.Ramalingam, S.S.Ramakrishnan, M.Priya Muthu Ramalakshmi, & M.Muneeswaran Institute of Remote Sensing, Anna University, Chennai - 600 025, Tamil Nadu, India Received 01 August 2014; revised 10 October 2014 Desertification is one of the fundamental hazards threatening the arid and semi-arid regions on ecological as well as economic perspective. Mapping and quantifying the land degradation have become urgent tasks in order to avoid the depletion or deterioration of the resources we need to know the causes for the depletion. In this study, the desertification status and the severity of desertification were studied using remote sensing and field data at Virudhunagar district, Tamil Nadu region, in south India. Modified Medalus method was used to identify the ecological sensitive areas (ESA) with landuse, climatic controls, soil quality, ground water quality and demographic factors. A number of indexes were prepared from the above parameters and the severity was identified by Environmental Sensitivity Area Index (ESAI). The desertification severity was classified into three classes such as low, moderate and high. The desertification severity from 2003 to 2012 was increased from moderate (1.34) to severe (1.42) at Sivakasi and Srivilliputhur taluk, which is located in the western side of the study area. Results showed that climate and demographic pressure were the most important indicators for describing desertification process in the study area. [Keywords: Desertification; Desertification Severity, Land degradation; Medalus; Environmental Sensitivity Area.] Introduction UNCOD has noted that, mapping and quantifying the potential hazard zones for Desertification as a process of development purpose and timely mitigating this degradation in arid ecosystems is wide spread in hazard3. arid regions of the world. This process is influenced by biophysical, chemical and Over the years, a number of methods biological factors and it affects such ecosystems and models are developed to analyze the as plants, soil and human activities1. In the desertification process. Provisional methodology recent years, the government of India has for assessment and mapping of desertification planned to execute many projects to combat hazard was one of the major excercise used for desertification. However, it seems that due to assessing the desertification and land the extensive arid area the government is not degradation4. But when it comes to local level, adequate and need much attention together with only limited studies were carried out to assess long-term effective national and international the land degradation. Medalus model is one of cooperation to combat desertification. the best examples among them, which later Desertification is one of the fundamental named as environmentally sensitive areas hazards threatening the arid and semi-arid (ESA)5. This model was developed for regions on ecological as well as economical Mediterranean regions and provides good result perspective. The 1977 United Nations for that countries6, 7. This method identifies the Conference on Desertification (UNCOD) in environmentally sensitive areas by the use of a Nairobi described that, desertification as the number of indexes8. This is very useful method diminution or destruction of the biological for determining different classes of vulnerable potential of the land2. Recently, it was redefined areas to desertification9. This model successfully as “Land degradation in arid, semi-arid and dry used in some Middle-East countries 7,8,12,14. sub-humid areas resulting from various factors, including climatic variations and human In India, desertification is considered as activities3. It can be a serious hazard over socio- one of the major problems in recent years economic development as well as a barrier to because of it is overpopulated. More than 30% sustainable development on global communities. of the geographical area is undergoing the VANI et al.: ASSESSMENT OF ENVIRONMENTALLY SENSITIVE AREA AND DESERTIFICATION 1735 process of land degradation11. Mapping the land foothills have rich loamy soil with good degradation is important to understand the vegetation cover. Plains with black cotton soil desertification process. But, very limited studies (locally known as cortisol) are underlying have done land degradation mapping in India 11, calcareous formations. Virudhunagar district 12,13. Main scope of the study is to map does not have any perennial rivers. Vaippar, desertification to the local level and assessing Arjuna Nadi, and Gundar constitute the river the severity of the land degradation process by network of the district. Numerous streams and using two different years of data. For this study, rivulets, activated by the monsoon, feed these the modified Medalus model was used for ESAI rivers. The study area receives the rainfall under over two different year data. The severity was the influence of both southwest and northeast estimated based on the change detection. monsoons. However, the northeast monsoon chiefly contributes to the rainfall in the district. Materials and Methods Most of the precipitation occurs in the form of cyclonic storms caused due to the depressions in Area selected for this study was the the Bay of Bengal. Virudhunagar district, it is located in the southern part of Tamil Nadu (Figure 1). It has an LISS IV data from the two time frames area of 4419.06 sq. kms. The District lies (March 2003 and March 2012) have been taken between 9° 12’ and 9° 46’ north latitude and 77° and used for this study. Geometric correction 20’ and 78°25’ east longitude. and radiometric correction were carried out for the above images. All the images were georeferenced and converted to UTM projection, WGS 84 datum. All the statistical data were collected from Department of Agriculture, Government of Tamil Nadu and Government of India. Desertification severity depends on various parameters and the quantification should consider all the major parameters which are involved in this process. The adopted methodology is explained in the following Figure 2. Based on the Medalus method, only the parameters which are suitable for the study area were taken for desertification quantification assessment. And some of the sub-indicators are also modified according to our study area. For vegetation quality index, a landuse classification proposed by SAC (ISRO) was used to study the desertification severity. There are five indexes Figure 1: Map showing the Virudhunagarstudy area. prepared for this study based on the factors like Insets show the location of the study area in Tamil Nadu state and India. climate quality, soil quality, vegetation quality, demographic quality and ground water quality. Virudhunagar district is The ground water quality index and soil quality physiographically divided into two types; the index have been calculated from the ground higher elevated lands and Flat plains. A major verified information. Each sub-indicator was portion of the district is covered by plain quantified according to its quality and given a topography. Eastern slopes of the Western weightage between 1.0 and 2.0 by the factorial Ghats cover a small part of Srivilliputhur and scaling technique and classified as high, Rajapalayam taluks. Black soil plains of moderate and low. After that, the indicators are Sivakasi, Virudhunagar, Sattur, Aruppukkottai, grouped and combined in quality layers such as Tiruchuli and Kariapatti are the remaining area. Climate Quality Index (CQI), Soil Quality Index The average height of the hills of the eastern (SQI), Vegetation Quality Index (VQI), slopes of the Western Ghats is 1500 m, though a Demographic Quality Index (DQI) and Ground few peaks rise to the extent of 1750 m. The 1736 INDIAN J. MAR. SCI., VOL. 44, NO. 11 NOVEMBER 2015 Water Quality Index (GQI). Then, the ESAI was area comes under the semi arid and the CQI prepared by the following equation (Eq 1)14. states that, the quality is decreased from the years 2003 to 2012 from 1.14 to 1.31. The ESAI = (CQI * SQI *VQI * DQI * GWQ)^(1/5) eastern side villages get low rainfall in these (Eq 1) years and the ET also reduced in these portions of the district. In 2003, Sattur taluk have high severity and in 2012, Sattur and Virudhunagar taluk shows high severity and the remaining taluks have moderate severity. Aridity index shows that, Sattur and Virudhunagar taluk has turned from semi-arid zone (2003) into an arid zone (2012). The Srivilliputhur taluk has turned into semi arid from sub humid in these periods. Other areas remained as semi-arid area, but the ET was getting lower in that period because of the low rainfall and vegetal degradation. Figure 2 Methodology flowchart for the Medalus method On the basis of computed ESAI, the quality of desertification was assessed for two years from 2003 to 2012. Results and Discussion The General physiogeographical condition of this study area shows, most of the Figure 3 Climate Quality Index of Virudhunagarfor area comes under semi-arid region. After the 2003 computation of ESAI, a detailed analysis was carried out for all the parameters and discussed below. Indicators that considered for the climate indices are precipitation, evapo- transpiration and aridity index. Figures 3 and 4 shows the Climate Quality Index (CQI) of the study area for the