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WHAT IS HAZARD MAP?

by Swesha Dhamala | 30-03-2020 15:17


Any hazard map has its specific purpose. So, hazard mapping is guided by the following three principles: (i) Avoidance
 (ii) Mitigation
 (iii) Control Depending upon the needs and resources, we have to avoid, mitigate or control a given danger. Consequently, the effort, cost, time and rigor to prepare a hazard map must be justifiable within the framework of its use. Hazard maps are generally prepared on a scale of 1: 25000 to 1: 50000 based on a combination of desk study and field study.

 In the desk study, pre-field maps are prepared to show the causative factors in the study area with the help of aerial photographs, satellite imageries, topographic maps and geological maps. The pre-field maps thus prepared include slope-morphometry, relative relief, land-use and land-cover, lithology, structure, soil depth, soil type and hydro geological maps. This information helps systematic planning and excursion of field. During the field study, more detailed structural & lithological, soil-depth, soil type, hydrogeological maps are prepared. The details of pre-field maps prepared are verified in the field and modified if necessary. Field studies are carried out to collect the required data-facet to estimate the total hazards of the facet.
The preparation of hazard map is based upon the identification of various hazard components followed by a rating of these components. Finally, all rating values are augmented. Before this, basic maps for the hazard mapping are prepared which include slope-map, soil-depth map, soil-type map, geological map, structural map, hydro- geological map, relief map, landslide, inventory map, land use etc.

 For each spatial area, some eating has been assigned to each attribute whatever present within the area. The rating values for each map are calculated. After that, according to the superimposition methods, all these thematic maps are overlapped one by one giving their rating values to each map for hazard assessment. These values are added. Then the area is divided into low, medium and high hazard levels on the basis of final values. In this way, the hazard map can be prepared