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Geographical Information System

Abstract :
Natural disasters are not inevitable however it is almost impossible to fully recoup the damage caused by the disaster. It is however possible to minimize the potential risk by developing disaster early warning strategies, preparing and implementing developmental plans to foster resilience to such disasters and to assist in rehabilitation and recovery initiatives. Space technology plays a crucial role in efficient mitigation and management of disasters. This paper describe the role of remote sensing and Geographical Information System (GIS) in evolving a suitable strategy for disaster management and an occupational framework for their monitoring, assessment and mitigation. It also identifies gap areas and recommends appropriate strategies for disaster management using these technologies. 

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 Flood

 Earthquake

Introduction
The Indian subcontinent is prone to all type of natural disasters: floods, droughts, cyclones, earthquakes and forest fires. Disasters can be classified in several ways A possible sub-division of disaster is: 1) Natural Disasters; 2) Human made disasters; 3) Human induced disasters. Another sub-division is related to the main controlling factors leading to a disaster and these may be meteorologically, geomorphological/geological, ecological, technological, global environmental and extra terrestrial. Another useful distinction that can be made between disasters is that regarding their duration of impact and the time of forewarning. Some disasters strike within a short period with devastating outcomes; others have a slow onset period with equally or even more serious repercussions. According to the available statistics 60% of the total area of the Indian subcontinent is vulnerable to seismic activity of varying intensities, 16% of the country's total area is drought prone. In India 68% of total sown area of the country is drought prone. Coastal areas of India are exposed to tropical cyclones and river floods are the most frequent and often the most devastating. 

Remote Sensing and GIS in the mitigation of natural disasters can only be successful when detailed knowledge is obtained about the expected frequency, character, and magnitude of hazard events in an area. Although, natural disasters have shown in the last decades a drastic increase in magnitude and frequency there has been an concomitant and drastic increase in technical capabilities to mitigate them. 

We now have access to information gathering and organizing technologies like remote sensing and GIS, which have proven their usefulness in disaster management. Remote sensing and GIS provides a data base based on the experience of previous disasters which can be drawn upon the produce hazard maps indicating which areas are potentially dangerous. Using remote sensing data, such as satellite imageries and ariel photos, allows us to map the variation of terrain properties, such as vegetation, water and geology, both in space and time. Satellite images give a synoptic overview and provide very useful environmental information, for a wide range of scales, from entire continents to the minute detail of a few meters. Many types of disasters, such as floods, droughts, cyclones, volcanic eruptions, and so on will have certain precursors that only a satellite can detect. Remote sensing also allows for monitoring of the event during the time of occurrence of the disaster in question. The vantage position of the satellite makes it ideal for us to think of, plan for and operationally monitor the event. 

Finally, the impact and departure of the disaster event leaves behind an area of immense devastation. Remote Sensing can assists in damage assessment monitoring, providing a quantitative base for relief operations. After that it can be used to map the new situation and update the database used for the reconstruction of an area. It can help to prevent the recurrence of such disasters in the future. 

Disaster Management
The use of remote sensing and GIS has become an integrated, well developed and successful tool in disaster management, as we have our own earth observation programs, and the requirement for hazard mitigation and monitoring rank high in the planning of new satellites. A very powerful tool in combination of these different types of data is GIS. It is defined as a "powerful set of tools for collecting, storing, retrieving at will, transforming and displaying spatial data from a real world for a particular set of purpose". GIS allows for the combination of different kinds of data using models. GIS allows for the combination of the different kinds of spatial data, with non-spatial data, attribute data and uses the information obtained in various stages of disaster management. 

A complete strategy for disaster management is required to effectively reduce the impact of natural disasters which is as referred to as the disaster management cycle. Disaster management consists of two phases that takes place before disasters occurs, disaster prevention and disaster preparedness, and the three phases that happens after the occurrence of a disaster i.e. disaster relief, rehabilitation and reconstruction. In the disaster prevention phase, GIS is used to manage the large volume of data needed for the hazard and risk assessment. In the disaster preparedness phase it is a tool for the planning of evacuation routes, for the design of centers for emergency operations, and for integration of satellite data with other relevant data in the design of disaster warning systems. In the disaster relief phase, GIS is extremely useful in combination with Global Positioning System in search and rescue operations in areas that have been devastated and where it is difficult to orientate. In the disaster rehabilitation phase GIS is used to organise the damage information and the post-disaster census information, and in the evaluation of sites for reconstruction. Hence, GIS is a useful tool in disaster management if it is used effectively and efficiently (Pearson et al., 1991). 

 

 Disaster Risk Management Programme
 [ MHA (Govt. of India), UNDP ]
Jointly Implemented By : Gujarat State Disaster Management Authority &
United Nations Development Programme

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United Nations Development Programme