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social negative impacts of forest fires (Küçükosmanoğlu, 1986; Garbolino et al., 2017) cannot be ignored. It is life threatening for people if forest fire goes beyond the scale that can be controlled and turns into a gigantic fire (Molina-Terre´N et al., 2019). Restoration and rehabilitation of areas destroyed due to forest fire require high cost, long time and a big labour force (Eker and Çoban, 2009; Naama et al., 2019). Therefore, forest fires should be detected and extinguished in the shortest time possible (Cao et al., 2019). Along the south and west coast of Turkey, forests that are distributed in areas adjacent to the Mediterranean and Aegean Sea and under the influence of Mediterranean climate are first-degree fire-sensitive areas (Bilgili et al., 2001; Bilici et al., 2017; Çoban and Erdin, 2020). This region also contains special conservation areas such as national parks, wildlife promotion areas and archaeological conservation sites. Uninterrupted lookout throughout the fire season is extremely important for these high fire-risk areas.
The statistics of the European Union show that 63724 forest fires that broke out in Turkey from 1988 to 2017, 319 848 hectares burned down (JRC, 2018). More than 90% of those forest fires are man-made (Avci et al., 2009; JRC, 2018). Every year more than 10 thousand hectares of forest area is burnt in Turkey (GDF, 2019). These figures indicate that Turkey faces a serious threat of forest fire.
When fire prevention fails, firefighting process starts (Çanakçıoğlu, 1993). The first step of this process is to immediately identify the origin of the fire. It depends on noticing fire in the short time possible to extinguish it before it grows further. Delayed action of identifying the fire ignition location also delays response by the first teams and that may allow the fire to grow bigger and burn large areas (Rodrigues et al., 2019).
In Turkey, the primary method used for early detection of forest fire is the network of fire lookout towers installed on 774 lookout points (GDF, 2019). Being installed for an effective fire detection system and playing an important role for the success of first response to fire, this lookout system reduces the fire extinguishing costs substantially (Rego and Catry, 2006; Catry et al., 2007; Pompa-Garcia et al., 2010). Two people assigned at towers lookout for possible fires with binoculars uninterruptedly 24 hours a day for almost 4 months. When fire is detected from the tower, the coordinates of the fire point are determined and emergency response teams are alerted. Tower officers monitor the status of the fire on one hand while on the other hand they navigate the teams in the field. Moreover, in fire-sensitive Mediterranean and Aegean regions, there are only a few fire lookout towers that are endowed with smoke detection sensors and thermal camera systems (Kolaric et al., 2008; Wooster et al., 2013). These sensors are reported to have a very high rate of sensing fire as long as they are not influenced by mist and fog (Küçük et al., 2017). In case of a meteorological alert, mobile first response teams and air surveillance (helicopters/planes) can be mobilized in the forest areas that are very sensitive to fire.
Fire lookout towers in Turkey are reported to have been built in 1946 (Çanakçıoğlu, 1993). Visibility analyses, that was once made on printed maps, can now be performed more quickly, precisely and with multiple dimensions in digital settings. Geographical Information System (GIS) is an effective tool to process digital surface data (Çoban and Eker, 2010; Yener, 2013) and to assess the locations of fire lookout towers on digital maps according to the designated criteria (Aºkın, 2004). In addition to the positioning of visible and invisible areas from the towers, GIS-based multidimensional assessment can be made through viewing the fire-sensitive areas from minimum two towers, processing and inquiring dangerous areas, picnic sites, energy transmission lines agricultural fields and settlement areas on different geographical layers. There are relatively few studies about the viewshed analyses at forest fire lookout towers in Turkey. In a study conducted in Boyabat in the West Black Sea Region, 73% of the forest area was reported to be visible from 6 fire lookout towers (Küçük et al., 2017). Another study was conducted in Ilgaz which was located in the same region (Kudu and Buğday, 2019). In a study conducted in Gallipoli Peninsula, 73% of the forest area was reported to be visible from 14 towers (Akbulak and Özdemir, 2008). Aºkın (2004) conducted a study in İzmir in the west, Akay et al. (2011) performed a study in Andırın in Kahramanmaraº region and Akay and Erdoğan (2017) conducted a study in Dursunbey-Balıkesir.
Fire lookout towers are an indispensable communication system despite the technological developments regarding the sensation of fire and notification of response teams about the fire including its location. The main function of these towers is the scanning of an area by a watchman on a regular basis at certain intervals. Therefore, these towers should be positioned in locations where a wide physical space can be visible and that have a wide field of view. There is a need to determine and assess the viewshed capacity of these towers that were positioned mainly on the basis of two dimensional map cross-section in the past. Several destructive fires break out in the Mediterranean forest ecosystems where first-degree fire-sensitive brutian pine and black pine species are widely distributed (GDF, 2019). Today, the effectiveness of the existing towers can be determined through analysis and assessment processes based on GIS that is capable of processing fine data such as digital maps and satellite data.
The objective of this study was to conduct visibility analysis of fire lookout towers by using GIS techniques, determine the visible and invisible areas and analyse the fire risk of