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(Ruiz, 2000). In Turkey, Küçük et al. (2017) and Göltaº et al. (2017) also conducted viewshed analysis, in which they used 10 km as the detection radius. As understood from these studies, the visibility of towers is lower in areas where the terrain is rolling/rugged.
The forest authority expects 70% visibility from the towers on rugged terrains. However, two-thirds of the towers in the area does not meet this expectation. This raises the following question: although the forest authority constructed these towers, why are most of them below the visibility standard it expects? To answer this question, we need to know the circumstances then. When these towers were constructed, digital data, computer technologies and GIS software were not available. For that reason, digital topographic models were not used. The findings of this study demonstrate that the location of fire lookout towers was not identified optimally. When a tower location was selected, the visible and invisible areas from a tower to be placed at that location could be automatically calculated through viewshed analysis. However, only printed maps were used at that time, it was not possible to make such calculations. Moreover, cost is one of the important elements to select the location of a tower. Maybe a more reasonable location was selected instead of constructing the towers at very steep and stiff locations without any roads.
Figure 7 shows that some of the forests that were in the scanning range of the towers but not visible were at high fire risk. This may be due to two reasons: first, as fire risk analysis and three-dimensional analyses were not performed for the construction of the towers, a mistake was made in the selection of the towers location. Secondly, as the terrain in the area where the forests were situated was highly rugged, observation capability is limited. This is definitely an optimization problem (Korkmaz, 2004). However, it can be suggested that the location of the towers in the existing lookout network, that does not rely on an optimization solution, does not meet the expectations.
The scientific studies conducted in Turkey demonstrate that the average visibility rate of the regional fire lookout systems is below the standard. Küçük et al. (2017) reported that towers could view 47% of the overall area and 52% of the forest areas in a study they conducted in West Black Sea Region. In other studies, 52%, 47% and 49% of the overall area were reported to be visible from the towers in studies performed by (Aºkın, 2004; Kudu and Buğday, 2019; Göltaº et al., 2017), respectively. According to the studies conducted in Turkey, the network of towers with the highest visibility rate is in Gallipoli Peninsula with 76% (Akbulak and Özdemir, 2008). These findings demonstrate that the fire lookout systems performed less than expected by the forestry authority. This is basically because the locations where the towers were positioned were determined according to the graphical calculations on printed maps rather than utilizing the data from digital elevation model. It is now possible to position towers with economically optimal (Korkmaz, 2004) and desired visibility rate using digital data and GIS (Bao et al., 2014; Shi and Xue, 2016).
There are only a few studies conducted in Turkey in which the network of fire lookout towers was overlapped with forest fire risk zones. Küçük et al. (2017) reported that 6% of the relatively high fire risk forest areas was invisible, 15% was outside the effective detection range. In this study, 15% of the forest area was found to be outside the detection range and have relatively high fire risk. Taking into account these risks, we think that a more effective lookout system should be constructed in forests at high fire risk through sensitive forestry activities (ªentürk, 2018). The forest authority is aware of the fact that fire lookout towers are not sufficient in certain areas. It tries to raise awareness of local people to fight forest fires in order to compensate these gaps. Through nation-wide public awareness-raising activities, people are advised to contribute to the prevention of forest fires and notify authorities immediately in case of a fire.
The fire statistics regarding the study area from 2008 to 2018 reveal that 70% of the fire reports were submitted by citizens to the security units or fire notification line of forestry authority. Fire reports from the towers have been decreasing, especially following 2010. This is because people use mobile phones more commonly and they can directly notify the security units about the fires that occur in places close to highways where especially there is heavy traffic (Eker and Özer, 2015).
People using the inner forest roads lead to the start of forest fire on one hand due to reasons such a cigarette litter and picnic fire while on the other hand they increase the success of first response by notifying the forest authority immediately if they see a fire while travelling through these roads (Narayanaraj and Wimberly, 2012; Ricotta et al., 2018). The records show that notification in this way is much earlier than the recognition by towers (IRDF, 2018). Almost everyone has a mobile phone today, this means that every conscious individual is a fire observatory. Therefore, it can be suggested that forests that are adjacent to settlement areas and visible from the frequently-used roads are under constant observation.
Fire lookout towers not only recognize fires in the shortest time and notify the fire response teams but also provide logistic support to them during fire extinguishing activities (Belval et al., 2019). We think that the tower lookout network will continue to be used as primary system in dangerous areas, protected areas and sensitive areas. With future technological developments in digital camera systems, thermal sensors and unmanned aerial vehicles, they can be more commonly used for fire observation. We think that it