Vulnerability Mapping and Resettlement plan for Baratang Island, Andaman, India.M.Arulraj Scientist, Geoinformatics Division NRSA Hyderabad. arul_gi@rediffmail.com P.Kasinatha Pandian Scientist, Institute of Remote Sensing Anna University Chennai. S.Ramachandran Professor, Institute for Ocean Management Anna University Chennai. ABSTRACT Tsunamis are scientifically described as a series of very long wavelength ocean waves caused by the sudden displacement of water by earthquakes, landslides, or submarine slumps. A great earthquake occurred off the West Coast of northern Sumatra on 26th December 2004 triggered giant tsunamis in the Indian Ocean that devastated the coastal regions of Indonesia, Malaysia, Thailand, Srilanka and India. In India, the impact was quite severe in the coasts of Andaman and Nicobar group of Islands. This tsunami has left a feeling that we need to be better prepared for such events. It is necessary to prepare a coastal vulnerability map to assess the areas, which are vulnerable to coastal disasters. Therefore, an attempt has been made for Vulnerability Mapping for the Baratang Island in Andaman group of Islands. In general, seven parameters such as elevation, geology, geomorphology, sea level trends, horizontal shoreline displacement, tidal ranges and wave heights are considered to demarcate the vulnerability line all along the Coast. But a vulnerability study based on wave travel and flooding should be the first step in the setting up of an all-hazards warning and management system. Since the run-up cannot be calculated, the safest and easiest option for the identification of the potential inundation zone is to define it as the area between the coastline and the contour of the highest recorded tsunami. The Tsunami affected areas are observed well with in that 0-20 m contour region of Baratang Island. Even though there are no much damage/lives lost observed, ultimately the settlements in this zone should be moved away to avoid damages in future. For this resettlement plan, thematic layers such as Landuse / landcover, transport, CRZ, Slope and Disaster prone areas are integrated in ArcGIS to suggest suitable sites for Resettlement. INTRODUCTION Tsunami, meaning "harbor wave," are scientifically described as a series of very long wavelength ocean waves caused by the sudden displacement of water by earthquakes, landslides, or submarine slumps and are mostly caused by earthquakes of magnitude 7.5 or greater. Tsunamis are rare in the Indian Ocean as the seismic activity is less than in the Pacific. A great earthquake on 26th December 2004 measuring M 8.6 occurred off the West Coast of northern Sumatra (Indonesia) at 06:28:51 hrs triggered giant tsunamis that devastated the coastal regions of India. In India, the impact of the tsunami was quite severe in the coasts of Andaman and Nicobar group of Islands (GSI 2005). The entire belt of Andaman & Nicobar group of Islands is an area of intense seismic activity and therefore has been included in the highest hazard class V of the Seismic Zoning Map of India. So the entire Andaman is prone to various disasters such as earthquakes, Tsunami and Cyclones. This tsunami has left a feeling that we need to be better prepared for such events (NIO, 2005). Vulnerability mapping and Resettlement plans are the important folios of hazard preparedness. Global Scenario A coastal hazards database for the United States (US) Gulf Coast, US East Coast and US West Coast were already developed by United States Geological Survey including the Risk variables such as Elevation, Geology, Geomorphology, Sea level trends, Horizontal shoreline displacement, Tidal ranges and Wave heights. In New Zealand, the vulnerability map was prepared based on the rate of erosion and flooding of coastal areas. In United Kingdom, the vulnerability maps were prepared on the basis of erosion and flooding. For Gulf of Corinth, Greece, Tsunami vulnerability assessment was made based on documented highest ever Tsunami run-up elevation and the characteristics of each building, Sea defense and natural environment. Hazard Intensity Rank definition for various coastal hazards including Tsunami inundations, Coastal Stream Flooding, High Waves, Storm Overwash and/ or High Winds, Coastal Erosion, Sea Level Rise, Volcanism and/or Seismicity were derived for county of Kauai ranges from low to High. Study Area In India nearly 150 million people are prone to natural hazards in coastal area. Bay of Bengal is one of the five cyclone prone areas of the world (Ramachandran, 2001). Andaman and Nicobar group of islands are located in the eastern Bay of Bengal. Soon after the earthquake on 26th December 2004, a tsunami wave of 2 to 10 meters followed in south Andaman to Nicobar Islands. The effect is that low lying areas from South Andaman to Nicobar group of islands sunk between 1 and 4 meters and as a consequence large land areas have been submerged (Kulkarni 2005). In many ways, the tsunami had a larger impact on the Islands than on the mainland. Since the Scientific principles in coastal zone management plan are i) Zonation ii) Vulnerability mapping and iii) Setback Zones (IOM 2003); it is necessary to prepare a coastal vulnerability map to assess the areas prone to coastal disasters. For this case study, Baratang Island in the Andaman group of Islands located in the northern part of south Andaman Island, between latitudes 12°03’26”-12°19’02”N and longitudes of 92°44’21”- 92°53’32”E is chosen to demarcate the Vulnerable areas and suitable sites for Resettlement plans. It is 35 nautical miles away from PortBlair city and connected with other islands by ferry services (Fig 1).  Fig 1 Study Area METHODOLOGY The Coastal Zone is vulnerable due to wave action, flooding, monsoon waves, storm surges and tsunamis. The distance, waves can travel inland depends on the near-shore bathymetry, existence of rock outcrops, coral reefs, beach rock, slope of the sea shore, coastline and the hinterland, sand dunes and other coastal features. Setback lines for various developmental activities should be based on coastal wave propagation vulnerability mapping. Climate Change and Sea-Level Rise status in Asia-Pacific countries were discussed in-detail in the Conference on Climate Change in Asia-Pacific Region held in Japan, 2000. It was reported that India did not have the formal vulnerability assessment methodologies. So in this study, Papathoma model is used to map the vulnerability (Papathoma and Dominey-Howes, 2003) which considers the identification of the inundation zone without taking into consideration the tsunami source and offshore bathymetry in order to be simple, easy and realistic. Since the run-up cannot be calculated, the safest option for the identification of the potential inundation zone is to define the area between the coastline and the contour of the highest recorded tsunami. The methodology adopted in the present study is presented in the Fig.2.  Fig 2 Methodology for preparing Disaster Prone Areas and Resettlement Locations Thematic Database creation It is always better to have a spatial database of any area to make quick decisions during rescue and relief operations during any form of disasters. By analyzing these spatial databases, people may be moved to safer places either permanently or temporarily, based on the effect forecasted by the Disaster Mitigation Authorities. A base map, which consists of the entire drainage network, road network, jetty and other important features of Baratang Island, is delineated from the Survey of India Toposheet 1967. On the other hand thematic maps for this current study such as Landuse / landcover, transport network, Coastal Regulation Zone, slope and disaster prone areas are derived/delineated from IRS 1C PAN + LISS III 2001, IRS 1D LISS III 2003 and IRS P6 LISS III, March 2005 satellite imageries by georeferencing them using ERDAS Imagine software. Polyconic Projection system is used to project these spatial thematic maps to find out the area and length of the polygons and linear features of them respectively. a.Landuse/Landcover Manual for landcover/wetland mapping by SAC, 1991 is used as a specification to map the various landuse/ landcover features (Fig 3) by visually interpreting the IRS P6 LISS III, March 2005 imagery. Tonal variation due to water level rise and inundation are observed from the imagery and classified as Inundated area during Tsunami.  Fig 3 Landuse/landcover map -2005 b. Transport Network Transport network in Base map is updated with the help of PAN Merged LISS III image of year 2001 and further updated by using IRS P6 LISS III 2005 imagery C. CRZ map High tide line of the Baratang Island is delineated by analyzing the tonal variation in the IRS 1D LISS III 2003 imagery. Using the Buffer option the 500m line is drawn inside the Hightide line. The MoEF Coastal Regulation Zone (CRZ) classification techniques (MoEF, 1991) are adopted to map the Island into CRZ I, CRZ II, CRZ III and CRZ IV categories. d. Slope Map Arcview 3D Analyst is used to derive the slope map from the contour map of the study area. Then the slope map is reclassified into 0-10°, 10-20° and etc. RESULTS AND DISCUSSION Vulnerability Mapping Soon after the earthquake on 26th December 2004, a tsunami wave of 2 to 10 meters followed in south Andaman to Nicobar Islands (Kulkarni 2005). A vulnerability study based on wave travel and flooding should be the first step in the setting up of an all-hazards warning and management system (LHI 2005). Since the run-up cannot be calculated, the safest and easiest option for the identification of the potential inundation zone is to define it as the area between the coastline and the contour of the highest recorded Tsunami (Papathoma and Dominey-Howes, 2003). Contour map of the study area is overlaid on the landuse/landcover map and Inundated areas are observed. These observations fall well with in the 0-20 m contour region. It should be known, where the vulnerabilities are so that the pre-disaster planning efforts can be easily made (NOAA Coastal Services Center, 1999). So the area between the High Tide Line (HTL) and the 20 m contour line is demarcated as a vulnerable area to coastal disasters (Fig 4) where the rehabilitation plans are needed.  Fig 4 Vulnerability map Fig 5 Resettlement plan map Resettlement Plan Overlay analysis in GIS environment has been carried out in this study to derive the resettlement plan for Baratang Island, Andaman, India. All the thematic layers such as landuse/landcover, road network, CRZ, Slope and Disaster Prone areas are integrated using ArcGIS. Polygons and linear features of the above thematic layers are categorized and ranked based on their suitability to Resettlement plan. Based on the score (Table 1), suitable site for resettlement are identified. The result of the overlay analysis is shown in the figure 5. The area has been finally selected by excluding the 500 m line from HTL, Vulnerable Area, and Slope greater than 40° and Reserve Forest.  It is necessary to prepare a coastal vulnerability map to assess the areas, which are vulnerable to coastal disasters. The vulnerability guide should answer for i) which natural hazards affect their villages; ii) what geographical areas are vulnerable to the hazards; iii) what structures and infrastructure will be affected; and iv) to what degree they will be affected. In the present study, the inundated areas are observed well within that 0-20 m contour region. Here the vulnerability map is based on the area between the coastline and the contour of the highest recorded tsunami. Accuracy of the results can be further improved by adding the datasets about the socio-economic condition, Lineament and Elevation data (10m) into the database. Reference:
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