Spatial Modelling Techniques for Forest Fire Risk Assessments

The study attempted to give insight in the use of RS and GIS for fire management. Spatial modelling and analysis have been done in GIS environment for identification of areas prone to fire risk and subsequently response routes were suggested for extinguishing forest fires (Jain et al., 1996 and Porwal et al., 1997). Some of the necessary components contributing to the fire behaviour viz., fuel (vegetation types), topography (slope and aspect etc.) and the causes of fire (i.e., roads and settlements) have been given due weightages.

The study has been done in part of Rajaji National Parks covering an area of approximately 115 km2. The topography is variable within the altitude ranging between 300-700 m above msl. The climate is subtropical type with the temperature varying from 13.1oC in January to 38.9oC in May & June. The area is dominated by moist Siwalik sal forest, moist mixed deciduous forest, dry mixed deciduous forest, chirpine and shrubs.

Landsat TM false colour composite (FCC) and SPOT images on 1:50,000 scale have been visually interpreted to obtain primary map layers viz. Forest cover type map, density map etc. The contour map, road network settlement etc. have been obtained from Survey of India toposheets. This spatial data in the form of map was digitized and transformed in machine-readable form for integration of thematic information. However, before their integration (Fig. 7) these were converted into index map viz., fuel type index maps from forest cover type map, aspect and slope index map from the slope and aspect map and distance index from the road map.

Figure 7: Fire risk zonation model

Spatial modelling has been done to obtain the combined effect of fuel type index, elevation index, slope index, aspect index and the distance/accessibility index. Weightages have been assigned as per the importance of particular variable contributing in fire environment. In this case the highest weightage has been given to fuel type index because fuel contributes to the maximum extent because of inflammability factor. The second highest weightage has been given to aspect because sun facing aspects receives direct sun rays and makes the fuel warmer and dry. The model output i.e., cummulative fire risk index (CFRISK) value map was obtained by integrating in ILWIS.

0 0

Post a comment