DEVELOPMENT OF A DECISION SUPPORT SYSTEM IN GIS TO COMBAT FOREST FIRE

Abstract

Forests are subjected to various kinds of injuries out of which forest fire is the most consequential doing incalculable harm to the forests. After deforestation, forest fire is the most important cause of worldwide colossal damage to extensive forest area, destroying seeds, seedlings and young trees. Forest fires cause loss of timber, destruction to wildlife, retard the vital activity of forest crops etc. These fires can be natural or manmade. Repeated fires lead to partial or even total loss of woodlands and ultimately to the vegetation cover and humus. In India, about 2-3% of the forest areas are affected annually by fire, and on an average over 34000 ha forest areas are burnt by fire every year. Fire is a rapid combination of fuel, heat and oxygen; all the three elements have to be present before a fire can start and continue burning. The main factor affecting the spread of forest fire is the inflammable material i.e., type and characteristics of vegetation. Both overstorey and understorey vegetation are crucial as they present the total fuel available for the fire. Topography is one of the main factors influencing the fire behaviour. The impact of aspect and slope behaviour on forest fire has been widely reported. Among all these factors, slope is considered to be the most critical. Steep slopes increase the rate of spread because of a more efficient convective preheating and ignition by point contact. The spread of fire is more quick on south and south west slopes due to direct rays of the sun making them warmer and dry. Protection of forests against fire has become one of the most important tasks of the Government. However, such an objective cannot be achieved without the State Forest Conservation Service using technical equipment and effective means and latest methods of detecting and liquidating forest fires. In the present study, Decision Support System linked with the Geographical Information System was used to analyse the data of the Balphakram National Park, located in Meghalaya State of the country. A vegetation map was produced from the analysis of IRS LISS II FCC, dated 14.12.96, while slope and aspect data were derived from digitisation of contours and generation of digital elevation model. A probability model which incorporated vegetation, slope and aspect was used to generate the distribution of the probability of fire occurrences. The results show that in a total area of about 250 Sq.Km, approximately 1.87% of area falls under the category of "very high" prone to the fire followed by 1.7%, 0.84% areas respectively under the categories of "high" and "moderate". The study indicate that the fire rotation is the leading factor of fire occurrence, and suggests that neighborhood effect is a primary factor in the distribution of wildfires.