Ravi Jadhav and P.S. Thakker
Forestry and Environment Division (FED), FLPG/RESA
Space Applications Centre (ISRO),Ahmedabad
Regulated or controlled fire is a very useful and legitimate tool in forestry practices for accomplishment of specific purposes. For instance, natural regeneration of teak (Tectona grandis Linn.f.), sal (Shorea robusta Gaertn.f.) and deodar (Cedrus deodara (D.Don) G.Don f.) is intimately associated with the role of controlled fires, NCA (1976). However, uncontrolled fire, whether natural or manmade, can cause havoc, that too, in a short span of time. It is the greatest enemy of the standing vegetation. The total damage from the forest fires is very large. Wild animals are killed. Small trees and regeneration are often affected very adversely. Even the big trees are not spared if the fire is severe. Ground fire destroys the organic matter which is very necessary to maintain an optimum level of humus in the soil. Repeated annual fires may decrease the growth of the grasses, herbs and shrubs which may result in increased soil erosion. A study made by the Forest Survey of India reveals that 51% of the forest area in Assam and Gujarat, 93% in Arunachal Pradesh, 67% in Bihar, 69% in H. P., 46% in J & K,45% in Karnataka, 76% in M. P., 94% in Meghalaya and Orissa, 87% in Nagaland, 58% in U. P. and 33% in West Bengal is subject to repeated annual fires, Lal (1989).
Fire and grazing have resulted in eliminating tender species, and making hardy species more abundant. Bamboo has been almost wiped out from many parts of central India, on account of its being extremely sensitive to damage from fire.
Literature is implete with the studies that report on the extent of fire or the damage caused by the fire. Nichols (1987) has attempted to develop a Forest-fire Add System Technology (FAST) for operational use in detection and mapping of forest-fires. It was envisaged to provide in near-real time, the forest-fire information to fire management at the incident command post. Khan et. al. (1989) have used multi-date Landsat data for determination of areal extent of fire affected areas in parts of Betul and Hoshangabad Districts of (MP). Khan et. al. (1992) mapped the fire affected areas in Bandhogarh National Park (MP) using IRS LISS-II data. Ayanger (1992) has carried out mapping and monitoring of forest-fire in parts of Thane and Gadchivoli districts of Maharashtra through satellite remote sensing. However, all these studies/reportings are the assessment of the aftermath. None of them were suggestive of any measures that could have averted the disaster.
While it is not possible to asses the actual damage caused, according to the figures available in the Forest Survey of India report (1987), fire occurred as many as 17,852 times in the country bringing an area of 5,72,417 sq. km. under fire and causing loss/damage over 7 million rupees during the VI Five year plan. To avert these most disastrous and damaging incidents, preparation of the forest – prone area map is a first step. In the present study, an attempt has been made to prepare this map integrating the satellite and the topographical data through Geographic Information System.
Gir forest located in the Saurashtra Peninsula of Gujarat is the largest biologically intact continuos tract of forest and the only abode of the Asiatic Lion in the world. It is situated between 20o 40′ N to 21o 50’N and 70o 50’E to 71o 15’E longitude respectively. The total area of the forest is 1882.6 sq. kms out of which 1412.12 sq. kms has been constituted as GIR Sanctuary and National Park (PA). It supports a rich biodiversity comprising of about 450 recorded flowering plant species, 32 species of Memmals, 26 species of reptiles, about 300 species of birds and more than 2000 species of insects. (Singh 1996). The forest is rugged and hilly with elevation varying from 150.3 to 530.7 mtrs. above sea level. The area is draining by 7 rivers which originate and pass through the forest. The area has an annual rainfall of about 980 mm and mean monthly temperature vary from maximum of 44o C to a minimum of 10o C.
Importance Geographical Information System (GIS) in Fire Risk Area Mapping
The most important use of GIS is its ‘modeling capability’ i.e. constructing models of the real world from digital database. Simulating the effect of a specific process over time for a given scenario. Modeling is a powerful tool for anal; trends and identifying factors that affects them, or for displaying the possible consequences of planning decisions or projects that affects them, or for displaying the possible consequences of planning decisions or projects that affect resource use and management (FAO. 1988). Forest management can draw benefit a lot from such a capability for decision support systems.
Remotely sensed data particularly from the satellites, is in a ready-made spatial-data format for GIS. Thus it is playing a very important role in the utilization of GIS technology. On the other hand GIS technology is helping in overcoming classification errors of remotely sensed data due to “infinite number of combination of materials, angles, illumination, reflectance, emittance, temperature and other physico-chemical-biological parameters” by allowing satellite data on the same area such as elevation, soil, climate, etc. “Remote Sensing data, thus bears a synergistic relationship to GIS technology and undoubtedly will be a major source of both original and monitoring information on the earth’s environments in the future” (Parker, 1990).
Forest Fire – Main Causes
The causes of the forest fires can be classified in three main categories i) Natural, ii) Intentional/deliberate due to man and iii) Unintentional/accidental due to man.
Natural: Natural fires occur mainly due to lightning orsometimes due to rolling stones and rubbing of dry bamboos with each other in the strong wind. Nothing can be done to avert such fires.
Intentional/Deliberate: Intentional/deliberate are the ones most commonly reported. Fires are set in forests for inducing luscious growth of grass for better grazing. Villagers sometime set fire to drive away the game destroying their crops and to catch the wild animals running away. The enmity with forest staff is also responsible for incendiary activities in forest areas by neighboring rural population. Fires are also caused by villagers for collecting minor forest produce (mfp) like honey, mahua, flowers etc. that fall on the ground. Sparks from coal-fired railway locomotives may also cause forest fires. Nothing much can be done to prevent a fire if it is a willful act on the part of local dwellers. However, occurrence of the fire can be averted if it is the result of unintentional activities of the innocent tribals or the natural factors.
Unintentional/Accidental:Unintentional/accidental fires occur in a forest due to careless throwing of match-sticks and burning ends of cigarettes/bidis , carrying of naked fire by people passing through forests, spread of fire from labor camps and recreation or picnic sites. These are the factors governed by parameters like vicinity to settlements and distances from roads.For any area to be prone to fire depends on many factors such as vegetation type/density, soil type, humidity of the area, vicinity to settlements, distances from roads and the host of others. While it is not possible to account for the natural occurrences or the deliberate attempts, the areas prone to accidental fires can be mapped. The prominent among the possible factors leading to accidental fires are
Vegetation type/density: Dry and dense vegetation is obviously more susceptible to fire than the moist and sparse one. Vegetation with less than 10% moisture content ignite readily, while the moist take time in igniting/burning.
Climatic factors: Of the four environmental factors viz., climatic, edaphic, physiographic and biotic, climatic factors influence fires the most. The climatic regime determines the vegetation in a region and hence plays dominant role in ascertaining the fire-prone sites. Drier the climate, more prone would be the site.
Physiographic factors: Physiographic factors, viz., altitude, aspect and topography, influence climatic conditions, and therefore, indirectly affect the vegetation. Aspect: Aspect plays vital role in spreading of the fire. Southern slopes, exposed to direct rays of Sun are more vulnerable to catching fire.
Topography: It is an important physiographic factor which is related to wind behavior and hence affects the fire-proneness of the area. Fire travels most rapidly up-slopes and least rapidly down-slope.
Edaphic factors: Soil and vegetation are mutually dependent on each other. If soil influences growth of plants, vegetation adds to richness of soil and thus is an important factor (Lal, 89).
Distance from roads: The man, animal and vehicular movement and activities on the road provide enough scope for accidental/man-made fire. Nearer the roads, more would be the chance of fire.
Vicinity to settlements: The areas near to the habitats/settlements are more prone to fire since the habits/cultural practices of the inhabitants can lead to incidental fire.
Causes of Fire in GIR National Park
As far as Gir National Park is concerned, based on continuous observations over the years, the forest department associates the following reasons for fire-incidences in the Park:
- First and foremost reason for the forest-fires in the Gir National Park area can be associated with the illicit cutting and stealing of the wood in the area. To drive away the attention of the forest-department personnel, fire is intentionally created by those involved in this illicit activity.
- For clearing the roadside blockades from the inspection-paths, small fires are some times created by the forest department itself.
- Running of the steam engine between Sasan and Sattadhar has also been experienced as one of the most common cause of the fires in the Park area.
- Carelessness of the people coming for collecting minor forest-produces (MFPS).
- Camp fire by Maldharis during the winter season.
- Forest fires in the friges of the protected area by the near by villagers in want fresh grass in the next season.
- GIR P.A. is under constant threat by 1,50,000 pilgrims who visit religious places within the sanctuary area and lighting lamps during offering prayers and leaving them carelessly.
- Traffic in public highways within sanctuary and protected area.
Spatial database: Vegetation and fire frequency map with forest block, Road / Railway network and the most important is existing Water bodies in that area.
Non-spatial data on meteorological data on temperature, relative humidity (min, max, average), rainfall, wind (speed and direction), socio-economic data, other tabular data on litter, duft, humus, mor, mull and slash.
The spatial data will be mainly from RS data and Non-spatial data would be from other sources essentially from local meteorological stations Forest Research Institutes and concerned Forest Departments.
Database Design & Organization In GIS Environment
GIS database design and organization involves a total visualization of an operational system. Database design not only helps for a systematic database organization but also provides a level of flexibility for enhancement/ upgradation/ improvement.
Table 1: Weightage Assignment Pattern For Various Parameters Included In Fire Risk Area Rating Analysis
|Fire Rating Class||Vegetation class||Proximity Road/Sett./Fringe||Max. Temp.(oC)||RelativeHumid.(%)||Fire Frequency|
|Very High||5 or 6||<= 100 mtrs.||> 40oc||<= 35 %||03|
|High||3 or 4||<= 500 mtrs.||> 40oc||<= 35 %||03|
|Medium||3 or 4||<= 1000 mtrs.||> 40oc||<= 35 %||< 03|
|Low||2 or 3||<= 1000 mtrs.||<= 40oc||>= 35 %||<= 02|
|Very Low||1 or 2||<= 1000 mtrs.||<= 40oc||>= 35 %||0 (Nil)|
|No Risk||Water Bodies|
Spatial Data Domain
The spatial data is mainly from Remote Sensing and ancillary sources. Most of the spatial data source follows the SOI (Latitude-Longitude) polyconic co-ordinate system. Thus the spatial database followed the standards of SOI maps at 1:50,000 scale. The primary data input sets are mainly thematic maps. These data sets have been either interpreted from RS data, prepared from ancillary data, Toposheets etc. or obtained from conventional sources or collected form Gujarat Forest Dept.(GFD).
Non Spatial Data
The non-spatial data sets were collected for each fire scar that included possible fire causes and meteorological data (max and min temp. and relative humid.) during the peak season. Since settlements or NES are also exists within sanctuary area, socio-economic data pertaining to these settlements were also incorporated in the non-spatial data sets.
The methodology adopted was Visual, Digital and Hybrid method for Remote Sensing data analysis. IRS 1C/1D LISS – III FCCs were used for visual interpretation for the classification of vegetation in the entire GIR – P.A. The standing vegetation had been classified into Six major classes. For mapping Fire scars digital analysis of IRS data had been used for the years 1990, 1991, 1997 and 1998. The methodology is shown schematically in the chart below.
Methodology for Forest Fire Risk Area Mapping
The basic themes generated for modeling the fire risk zone were:
- Fire Occurrence Maps for three or more seasons
- Classified Vegetation Map (two seasons)
- Road and Rail Network including forest roads
- Maximum and Minimum Temperature
- Relative Humidity
- Rain fall data
- Admin. Boundaries – Forest Blocks/compartments.
- Rivers, Streams and Waterbodies.
- Riverain Dense Forest
- Moist Deciduous good density
- Dry Deciduous good density
- Dry Deciduous open Forest
- Dry Deciduous Mixed (Degraded)
- Scrub/Grass Land (Vidis)
It is observed that Very High and High Risk zones are mostly at the fringe of the Protected Area or with in 100m of the roads passing through the region with temperatures above 40oc and Humidity less than 35%. It is observed that most of the fringe areas of the forest are facing frequent fire occurrences. So, it is very clear that biotic interference plays vital role in fire occurrence.
Apart from human interference, the analysis has also shown that Vegetation type and meteorological parameters have vital importance for hazard zonation.
Based on analysis carried out, a fire risk area map showing the Very high risk to No risk areas have been demarcated which will help the Forest Officials to take precautionary measures for controlling the fire occurrence. It also helps for the deployment of fire fighting equipment to those spots having high risk or to setup the watch towers for keeping constant vigilance over the area.
- Forest Fire Monitoring Using High Temporal Resolution Remote Sensing Data And Gis Techniques – A Case Study In Gir Forest (Sasan) – K.L.N. Sastry et. La.
- Forest Fire in Central Himalaya : An extent, direction and spread using IRS LISS-I data (Int.Jour. Remote Sensing, 1998, Vol.19, No.12) M.M.Kimothi and R.N.Jadhav
- Baseline Mapping Of GIR PA – Gujarat, Using Remote Sensing and GIS Techniques – An Interim Report – R.N.Jadhav et. La.
- “Application of GIS in Identification of Fire Prone Areas – A Feasibility Study in Parts of Junagadh (Gujarat)” (The Indian Forester Vol. 124, No. 07, July 1998) By A.K. Kandya, M.M.Kimothi, R.N. Jadhav and J.P. Agarwal
- “Forest Fire Monitoring Using Remote Sensing and GIS” GEOMATICS – 98 (Abstract) By K.L.N. Sastry et. La.
- ISG NEWSLETTER- Vol. 04, November 2 , News item – “Forest Fire Monitoring Using High Temporal Resolution Remote Sensing Data and GIS Techniques” By K.L.N. Sastry
- Forest Fire Prone Area Mapping – Acase study GIR P.A. (a technical report) by R.N. Jadhav, K.L.N.Sastry, A.K. Kandya, P.S. Thakker and M.M. Kimoti