Almost 20 % of wildfires recorded in Poland are forest fires (Fig.1). Surface fires contribute to 75% of all forest fires. The majority of these fires is not larger than 1 ha. However, an increase of large forest fires has been noted during the recent years. Figures 2 and 3 present data which show the increase of number of forest fires and burned areas in Poland. Especially dramatic was 1992 when 9,305 fires were recorded in Poland (three times more than in previous years); they affected 37,000 ha of forest (12 times more than in 1991). Long periods of drought and high air temperatures were the main reasons for such a great number of fires. Multiple environmental stresses and other influences are believed to create a new fire risk in Poland: impacts of the long-term droughts, forest decline due to air pollution, and high touristic traffic. The effects of forest decline lead to decay of trees, opening of the canopy, lush growth of grasses, hence large amount of available fuels).
In this situation, characterized by increasing fire risk and greater number of large fires, it is necessary to apply new techniques and technologies for fire prevention, e.g. remote sensing and GIS. There are three aspects of their application for fire management in Polish conditions:
Fire risk forecast for the whole country and for particular regions
Inventory of fire damages, assessment of losses, and monitoring of regeneration
Since 1982 the Forest Research Institute (IBL) in Warsaw has applied panchromatic aerial photographs for evaluating the extent of fires. Aerial thermal imagery was used by the Remote Sensing and Spatial Information Centre (OPOLIS) of the Institute of Geodesy and Cartography in Warsaw for detecting underground fires. Thermograms recorded by AGA Thermoprofile THP-1 scanner and colour equidensity thermograms produced with the use of an electronic-analogue viewer allowed the distribution of soil temperature and hence fire location to be determined. OPOLIS also has experience in utilizing colour-infrared aerial photographs for assessing the state of forest, especially for monitoring the long-term consequences of surface fires.
Research on the use of satellite imagery Research has been continuously followed for several years. In August 1992 the largest forest fire in Poland (9060 ha), located in the Upper Silesia region (Kuznia Raciborska) was observed on satellite images. The spread of this fire was exceptional in Polish conditions, and the increase of the burned area could be observed on NOAA AVHRR images. Smoke on these images was seen at a distance of 100 km. SPOT XS and XP images acquired in September 1992 and in May 1993, as well as ERS-1 images acquired in summer 1993, clearly present the extent of burns.
Both ERS-1 and SPOT images enable burnt area to be determined with the same accuracy. However, small clumps of trees which survived, could be better distinguished on the SPOT image, due to high near-infrared reflectance. Spectral characteristics for microwave images make discrimination of these clumps more difficult on ERS-1 images.
Forecasting of forest fire risk is the next application of remote sensing for fire management. At present the fire risk is determined on a daily base during the fire season (ca. 200-240 days). This fire hazard assessment is based on the measurement of moisture content of forest litter in permanent observation stations, following a method developed by the Forest Research Institute in Warsaw.
Recent studies of NOAA-derived information reveal relationships between soil moisture, vegetation state and evapotranspiration. As a result of these studies it was decided to test the potential applicability of NOAA AVHRR imagery for evaluating fire risk in Polish forests. The research goal is based on the assumption that indices derived from NOAA images correlate with parameters which determine forest fire risk.
Research on modelling fire risk, its origins, development and consequences has been started recently. Spatial information systems are useful tools in creating these models. The main elements of the models are: types of stands, species composition for particular forest storeys, archived forest data, topographic data, relief, as well as climate conditions. The Forest Fire Database (FFD) provides the base of the information system. FFD stores 32 types of information about forest conditions of burnt stands, meteorological conditions during a fire, type and acreage of burnt area, fire characteristics and fire control information. These data are used for forest fire hazard analysis. Together with information derived from forest maps these data are the base of Geographic Information System (GIS) for fire management purposes.
In 1992 joint work on creating spatial information system for Kuznia Raciborska burnt area and for surrounding forests was started by OPOLIS, IBL and the Laboratory of Remote Sensing and Forest Management of the University of Gent (Belgium). The area of investigation is particularly important for highly industrialized and polluted Upper Silesia region. The information system will be used for monitoring fire effects. It will be based on several information layers derived from archive forest maps, soil-site maps, topographic maps, as well as from aerial and satellite images and digital terrain models. A relational database, additional to FFD, will contain archive taxation descriptions of stands and updated information, characterizing reclamation works and results of monitoring environmental changes.
Furthermore it is planned to develop operational GIS-based fire prevention systems, based on spatial information layers (containing forest maps, updated by remotely sensed data), other related databases (describing taxation features of particular stands), fire risk forecasts, and fire alarm procedures.
Fig.1. Structure of fire occurrences in Poland (all sectors)
Fig.2. Number of forest fires and burned area in Poland, 1988-92
Fig.3. Increment of number of forest fires and burned area in Poland in the period 1961-92 (1961-80 = 100%)
From: Tytus Karlikowski and Tomasz Zawila-Niedzwiecki Address: Forest Fire Control Section of the Forest Research Institute ul. Bitwy Warszawskiej 1920r. No.3 PL – 00-973 Warsaw
OPOLIS-Remote Sensing and Spatial Information Centre Institute of Geodesy and Cartography 2/44 Jasna Str. PL – 00-950 Warsaw