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:
National level:
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.)
Regional level:
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.
Medium level:
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.
Local level:
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.
Conclusions
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