Samir Kumar Banger
DP Engineer, HOPE Technologies Limited
1 Navjeevan Vihar, New Delhi- 110017, India
Natural disasters are inevitable and it is almost impossible to fully recoup the damage caused by the disasters. But it is possible to minimise the potential risk by developing disaster early warning strategies, prepare and implement developmental plans to provide resilience to such disasters and to help in rehabilitation and post disaster reduction. 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 occupational framework for their monitoring, assessment and mitigation, identifies gap areas and recommends appropriate strategies for disaster management using these technologies.
Natural Disasters are inevitable, and Indian subcontinent is prone to all type of Natural Disaster either it is flood, drought, cyclone earthquakes or forest fires etc. 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. These may be meteorologically, geomorphological/geological, ecological, technological, global environmental and extra terrestrial. Another useful distinction that can be made between disaster is regarding their duration of impact and the time of forewarning. Some disaster strikes 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 Indian subcontinent is venerable 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 is exposed to tropical cyclones and among all the disaster occur in the country, River floods are the most frequent and often the most devastating.
Remote Sensing and GIS in Disaster Management Mitigation of natural disaster management can be successful only when detailed knowledge is obtained about the expected frequency, character, and magnitude of hazard events in an area. Although, natural disaster have shown in the last decades a drastic increase in magnitude and frequency, it can as be observed that there is a dramatic 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 from which the evidence left behind by disaster that have occurred before can be interpreted, and combine with the other information to arrive at hazard maps, indicating which area is potentially dangerous. Using remote sensing data, such as satellite imageries and ariel photos, allows us to map the variabilities of terrain properties, such as vegetation, water, geology, both in space and time. Satellite images give a synoptic overview and provide a very useful environmental information, for a wide range of scales, from entire continents to detail of a few meters. Many types of disasters, such as floods, droughts, cyclones, volcanic eruptions, etc. will have certain precursors that satellite can detect. Remote sensing also allows monitoring the event during the time of occurrence while the forces are in full swing. The vantage position of 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 operation. 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 occurrence f such disasters again in future.
The use of remote sensing and GIS has become an integrated, well developed and successful tool in disaster management, as we are having 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 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 use them as useful information in the various stages of disaster management.
A complete strategy for disaster management is require to effectively reduce the impact of natural disaster, which is as referred to as disaster management cycle. Disaster management consists of two phases that takes place before disaster occurs, disaster prevention and disaster preparedness, a three phases that happens after the occurrence of a disaster i.e. disaster relief, rehabilitation and reconstruction. In disaster prevention phase, GIS is used to manage the large volume of data needed for the hazard and risk assessment. In 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 the useful tool in disaster management if it is used effectively and efficiently (Pearson et al., 1991).
Remote Sensing and GIS for Different Application Levels
Natural Hazard information should be included routinely in developmental planning and investment projects preparation. Development and investment projects should include a cost/benefit analysis of investing in hazard mitigation measures, and weigh them against the losses that are likely to occur if these measures are not taken. Remote sensing and GIS can play a role at the following levels:
At national level, GIS can provide useful information, and create disaster awareness with politicians and the public, so that on a national level decisions are taken on the establishment of disaster management organisations. At such a general level, the objective is to give an inventory of disasters and the areas affected or threatened for an entire country. Mapping scales will be in order of 1:1,000,000 or smaller. The following types of information should be included:
- Hazard free regions for development.
- Regions with severe hazards where most development should be avoided.
- Hazardous regions where development already has taken place and where measures are needed to reduce the venerability.
- Regions where more hazards investigations are required.
- National scale information is as required for these disaster that affect and entire country (drought, major hurricanes, floods etc.)
At regional level the use of GIS for disaster management is intended for planner in the early phase of regional development projects or large engineering projects. It is used to investigate where hazards can be a constrain on the development of rural, urban or infrastructural projects. The areas to be investigated are large, generally several thousands or square kilometer, and the required details of the input data is still rather low. Typical mapping scales for this level are between 1:10,000 and 1:1,000,000. Synoptic earth observation is the main source of information at this level, forming the basis for hazard assessment. Apart from the actual hazard information, as environmental and population and infrastructural information can be collected at a large detail than the national level. Therefore, the GIS can be utilised more for analysis at this scale, although the type of analysis will mostly be qualitative, due to the lack of detailed information.
At this level GIS can be used for the prefeasibility study of developmental projects, at all inter-municipal or district level. The areas to be investigated will have an extend of a few hundred of square kilometer and a considerable higher details is required at this scale. Typical mapping scale is in the order of 1:25,000 – 1:100,000. Slope information at this scale is sufficiently detailed to generate Digital Elevation Models, and derivative products such as slope maps. GIS analysis capabilities for hazard zonation can be utilised extensively.
The level of application is typically that of a municipality. The use of GIS at this level is intended for planner to formulate projects at feasibility levels. But it is as used to generate hazard and risk map for existing settlements and cities, and in the planning of disaster preparedness and disaster relief activities. Typical mapping scales are 1:5,000 – 1:25,000. The details of information will be high, including for example cadastral information. The hazard data is more quantitative, derived from laboratory testing of materials and in field measurements. As the hazard assessment techniques will be more quantitative and based on deterministic/probabilistic models. The size of area under study is in the order of several tenths of square kilometer and the hazards classes on such maps should be absolute, indicating the probability of occurrence for mapping units, with areas down to one hectare or less.
Site investigation scale:
At site investigation scale GIS is used in the planning and design of engineering structure and in detail engineering measures to mitigate natural hazards. Typical mapping scale are 1:2,000 or larger. Nearly all of the data is of a quantitative nature. GIS is basically used for the data management, and not for data analysis, since mostly external deterministic models are used for that. As 3-D GIS can be of great use at this level.
Analysis of hazard is a complex task, as many factors can play important role in the occurrence of the disastrous event. Therefore, analysis requires a large number of input parameters, and techniques of analysis may be very costly and time consuming. The increase availability of Remote Sensing data and GIS during the last decades has created opportunities for a more detailed and rapid analysis of natural hazard. The proper structure of information system for disaster management should be present to tackle the disaster and to manage it. The remote sensing and GIS database can be used to create elaborate and effective Disaster Management Information System (DMIS). An integrated approach using scientific and technological advances should be adopted to mitigate and to manage natural hazards. Moreover there should be a national policy for natural disaster management.
Appendix 1 References
- Alexander, D., 1993. Natural Disasters. UCl Press ltd. University College London. pp 632.
- Cova, T.J., 1999. GIS in emergency management. In: Geographical Information Systems, management and applications. Longley, P.A.; Goodchild, M.F.; Maguire, D.J. and Rhind, D.V.
- Pearson, E, Wadge, G, and Wiscoski, A P, 1991. An integrated expert system/GIS approach to modeling and mapping hazards. Proc European conference on GIS, session 26, pp 763-771.
- Carter, W N, 1992. Disaster Management: A Disaster Manager’s Handbook Asian Development Bank, Manila.
- Natural Disaster Reduction, South Asian Regional Report. 1994. Proc. The SAARC workshop on Natural Disaster Reduction, March 1994.
- Sharma V K, 1999. Use of GIS related technologies for managing disaster in India: An overview. GIS @ Development, Vol 3.3, May-June 1999, pp 26-30.
- Environmental Modeling with GIS and Remote Sensing, 1999. International Institute for Aerospace Survey and Earth Sciences.
Appendix 2 Notations
GIS Geographical Information System