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A Digital Oil Spill Sensitivity Atlas for Mauritius using GIS

H. Runghen1, M. Bhuruth2 and S.D.D.V. Rughooputh3
1Department of Mathematics, runghenh@mx.uom.ac.mu
2Department of Mathematics, mbhututh@uom.ac.mu
3Department of Physics, sdr@uom.ac.mu
Faculty of Science, University of Mauritius, Réduit, Mauritius

One of the main challenges faced by countries, especially small island states, during an oil spill combat is the identification of vulnerable coastal locations. The lack of precise information of this nature has often led to the inappropriate use of combat materials and response strategies. In this study we present the application of GIS in the organization of information that will determine the degree of vulnerability in standard formats. Information on relevant factors such as shoreline sensitivity, biological resources, exposure to wave and tidal energy, and human-use resources are systematically presented using the Environmental Sensitivity Index technique. This paper presents an application taking Mauritius as a case study for oil spill preparedness. Significant factors affecting rescue efforts are investigated, as a result of which priorities are established and cleanup strategies identified. The paper shows the applicability of GIS tools and technology in governing actions taken during oil spill accidents, thus ensuring that the response is not only prompt but also appropriate. The methodology is demonstrated on a map of the North-West of Mauritius.

1. Introduction
Oil spill disasters have been a major concern due to increasing number of accidents that have occurred in recent years, for example, Sea Empress (1996), Pallas (1998), Erika (1999) and Prestige (2002). Since direct impact of oil spills in the marine environment are generally wide spread and of long-term, they can have devastating consequences on wildlife, fisheries, coastal and marine habitats, human health, economy as well as recreational resources of immediate coastal communities. Mauritius and its outer islands are located along a very dense maritime route for oil transportation. Tankers along this route carry around 750 million Metric tonnes of petroleum products annually. Every year 36 vessels of 6000 Metric tonnes and 23 vessels of 22000 Metric tonnes offload petroleum products in Port-Louis harbour. As a result, the Government of Mauritius through the Environmental Protection Act of 2002 mandated prescriptions of procedures for cleanup and removal operations. In this context, oil spill combat authorities have set up atlases that provide a means of determining marine and coastal areas of sensitivity that might be impacted should such a pollution incident occur. Many countries, such the United States of America, Australia, Greenland and Mauritius, have included oil spill sensitivity atlases as an integral part of their contingency plan.

The basic requirements for an understandable and usable oil spill sensitivity atlas have been discussed in the IMO/IPIECA report series [1]. Shoreline types, sub-tidal habitats, wildlife and protected areas, fishing activities and other socio-economic features as well as oil-spill response features are important factors to consider when setting up such an atlas. Another determining factor is the seasonal aspect which may alter the sensitivity of some resources. The inability of a hard-copy map to convey these complex logistics has significantly increased the use of Geographical Information Systems (GIS). Halls et al. [2], Fisher et al. [3] and Muskat [4] explain how GIS technology can be applied as a more efficient tool for oil spill preparedness, during an emergency response, and an aid for quantifying natural resource damage. GIS has proven to be an excellent data management, organizational and analysis tool. As the system becomes more widely used, the possibilities of linking different GIS systems and data required for oil spill response and contingency planning are increasing.

The aim of this paper is to present the different steps to build an oil spill sensitivity atlas using GIS technologies. The ESRI’s ArcGISTM 9.0 platform is chosen as it guarantees an efficient and effective means of managing geospatial data such as enabling easy alterations and updates. The Environmental Sensitivity Index (ESI) technique developed by the National Oceanic and Atmospheric Agency (NOAA) [5] is used to organize the information in standard formats for shoreline sensitivity, biological resources, exposure to wave and tidal energy and human-use resources. An oil spill sensitivity atlas for Mauritius was developed by Gunlach et al. [6]. In this paper the technique used to set up an updated and accurate oil spill sensitivity map is described. Based on all these information, appropriate methods to respond to oil spills in the different areas of Mauritius have also been assessed. Digital maps of Mauritius with scale 1:25,000 were used as base map for the thematic layers and listings of each processed data. Spatial and non-spatial data were analyzed through various functions of GIS techniques, such as geoprocessing, data analysis and overlaying, and modelling to yield the risk management system as thematic layers.

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