Preliminary Assessment of the Wildfire Risks as a Tool for Their Management. The Case of Bulgarian Forests

Abstract

The primary objective of this book chapter is to present an updated methodology for fire risk assessment, particularly in the context of Bulgarian forests. This update is essential due to the existing disparities among the tools and approaches used in previous assessments. The focus of this study is to develop a unified methodology for conducting preliminary risk assessments of wildfires, considering them as one of the most prevalent and natural disasters in forest ecosystems. The significance of such an updated methodology lies in the fact that different assessments can yield varying results for the same region, creating challenges for the development of sustainable land management plans and effective responses to potential wildfires. For instance, when using the approved national “Methodology for determining the risk of forest fires in the country” sanctioned by the Ministry of Agriculture, Food, and Forests (MAFF) of Bulgaria, which aligns with European requirements, some areas, like the territory of the State Forestry “Botevgrad” (TP SFE “Botevgrad”), were categorized as having a medium risk of wildfires. However, in the Forest Management Plan of TP SFE “Botevgrad,” the degree of wildfire risk was classified as low. In light of these discrepancies, we have taken the initiative to enhance the methodology by including risk calculations for smaller units, such as subdivisions, sections, and enterprises. This approach seeks to provide a more accurate and detailed assessment of wildfire risk in specific forest areas.

1 Introduction

Wildfires inflict substantial damage on forests and the forestry sector worldwide, with recent incidents in Europe highlighting the severity of the situation (Fernández-Anez et al., 2021). These fires generally have adverse effects on the economic, social, and environmental aspects of individual countries as well as the global ecosystem (Clarke et al., 2022). As a consequence of wildfires, substantial quantities of valuable timber are lost, and the condition of forest plantations is disrupted and deteriorated. Moreover, vast expanses of forested areas are deforested, compromising the protective functions of forests and diminishing their role in water protection. This leads to increased rates of soil erosion, particularly in mountainous regions.

According to wildfire statistics data (Stoyanov, 2021), the average annual area of burned forests in Bulgaria was 10,876 hectares during the period from 1995 to 2004. From 2005 to 2014, this figure decreased to 8,592 hectares, and between 2011 and 2020, it further reduced to 5,140 hectares. Despite the declining trend in the extent of wildfires in Bulgaria, they continue to pose a significant challenge and have substantial negative impacts on the state of forestry and the country's economy. As of 2021, Bulgarian forests cover 4,270,995 hectares, representing 38.7% of the total territory of the country, with the forested area accounting for 92% (Annual Report, 2021).

Forests in the Republic of Bulgaria can be categorized into different types, including state-owned forests (77.3%), municipal forests (11.2%), and those owned by public organizations, religious entities, or private individuals. Given this diversity, Assenova M. (2018) emphasized the importance of Geographic Information Systems (GIS) and the establishment of specialized databases to provide accurate data, relevant indicators, and updated maps. Such tools would facilitate the monitoring of wildfire risks, as well as the current and future forest conditions in Bulgaria. This, in turn, could enable the effective development of firefighting strategies and support the efforts of specialists across various sectors, including private enterprises, state forest management agencies, and their respective divisions and units.

2 Updating Methods and Standardization of Tools

The aim of this book chapter is to demonstrate how to update the existing methodology for assessing fire risks in Bulgarian forest areas, addressing the disparities among the tools previously employed. It’s worth noting that such disparities are not unique to Bulgaria, and in this chapter, we will explore potential approaches to tackle this uncertainty. To achieve this objective, we will administer a risk factor questionnaire designed to describe and evaluate the current conditions within a specific study area. These risk factors will be ranked according to their severity, allowing for a comprehensive assessment of the risk of forest fires within each forest enterprise, as well as its individual sections. The area of forestry sections is further divided into divisions and subdivisions, representing the smallest territorial units within forest enterprises.

First, we utilized the “Methodology for determining the risk of forest fires in Bulgaria” (Lyubenov, 2016), followed by a combination of data derived from both national sources (Annual Reports for the years, 2009–2021) and European sources (“Forest Fires in Europe, 2002–2021”) pertaining to forest fire statistics. Our intention is to propose a wildfire risk assessment methodology that not only ensures the accuracy of such assessments but also their practical applicability.

This approach is motivated by findings from “Determining the degree of risk of forest fires in TP SFE Botevgrad” (Stoyanov, 2021), which reveal that the approved methodology of the Forest Executive Agency (FEA) does not adequately account for wildfire risk at the levels of forest enterprises, sections, divisions, and subdivisions. Our scientific objective is grounded in the recognition that initial statistical information is often insufficient in terms of reliability and completeness. Additionally, certain information related to the fire hazard of forest areas is qualitative and cannot be quantified. Moreover, prolonging the data collection period can result in escalating evaluation costs. Furthermore, in the realm of researching complex systems and problems, including those encompassing fire safety, statistical information alone is often inadequate, necessitating the incorporation of specialized expert information, which includes normative and reference data. Models generated through the joint analysis of these two types of information are referred to as “Expert Statistical Models” (ESM).

In the context of addressing this problem, an Expert Statistical Model (ESM) should function as a mathematical representation of the relationship (function) between the level of fire hazard (safety), also known as the endogenous variable or output, and a vector of factors (exogenous variables or inputs) that influence it. The factors included in the questionnaire (checklist) and the descriptions of conditions are formulated such that responding “yes” always corresponds to 0, while responding “no” corresponds to 1. This formulation greatly simplifies the development of a software tool for automating the wildfire risk assessment process.

Wildfire risk, as defined, represents the mathematical expectation of the loss function’s value. Its constituent elements include the probability of hazardous factors associated with wildfires affecting forests and the magnitude of resulting losses. Assessing the overall wildfire risk involves considering components such as fire occurrence, fire detection, fire progression, and fire suppression, including efforts to minimize the impact of hazardous factors. These components, in turn, are directly influenced by a range of organizational, technical, natural, and social factors.

3 Presentation of the Obtained Results for the Case of Bulgaria

In the initial stage, risks are assessed through expert evaluations to identify forest areas that require primary fire protection. Simultaneously, a preliminary risk assessment is conducted based on the most adverse (extreme) conditions and factors that could result in maximum risks. This assessment utilizes actual indicators observed on the day of the evaluation.

The integrated forest fire risk index (R₀) is determined by the formula:

$${R}_{0}=F\left(\overrightarrow{a,}\overrightarrow{x}\right)={\sum }_{i=1}^{4}Bi(\sum_{j=1}^{k}{A}_{ij}{a}_{j}+\sum_{j=k+1}^{I}{A}_{ij}{x}_{j}$$

(1)

where:

$$\overline{a }=a1,\dots ,ak$$

(2)

– vector of uncontrollable parameters, expressing the quantitative values of various factors (natural, social, organizational, and technical);

$$\overline{x }= (xk+1,\dots ,xl$$

(3)

• – vector of controlled parameters, the values of which may change when planning a system of measures to reduce the risks of forest fires;

• Bi—the coefficient of the significance of the i-th type of fire hazard in the integrated assessment (i = 1, …, 4);

• Aij—weighting factor, which takes into account the effect on the i-th type of fire hazard of the j-th parameter (uncontrolled—at j = 1, …, k; controlled—at j = k + 1,…, l).

Equation 1 is employed to calculate the integrated forest fire risk index, with the values achieved during the study being assigned to the controlled parameters. This proposed approach for determining forest fire risk can be characterized as a rapid method for risk assessment. Implementing this method will enable a practical evaluation of wildfire threats, identification of the most vulnerable forests, communities, and forested areas, and contribute to enhancing their fire protection measures.

3.1 Risk Assessment of Wildfire Factors

The process of assessing wildfire risks involves several key steps:

• Gathering information about the state of fire safety in forested areas, including reports, collected data, forest inventory records, fire safety plans, and other relevant documents.

• Evaluating the fire hazard within the region, taking into consideration factors such as the condition of forested areas, the presence of fire-prone sites, and the maintenance of forested lands.

• Assessing the effectiveness of measures implemented to ensure compliance with forest fire safety regulations, management practices, and other organizational and technical measures.

• This information is collected through a combination of surveys conducted by administrative personnel, forestry experts, and land tenants. It also involves accessing statistical, technical, and forest inventory data, as well as conducting on-site inspections.

Subsequently, the gathered data is analyzed to derive both qualitative and quantitative insights into the wildfire risk levels. If the risk level is deemed acceptable, an action plan is developed, including prioritization of tasks and a timeline for future assessments. However, if the fire hazard is determined to be extremely high, immediate measures must be taken to enhance protection against forest fires.

3.2 Identification of Wildfire Risks

The assessment of wildfire risk involves identifying and evaluating all foreseeable and significant factors that could contribute to the occurrence of a wildfire. This includes an examination of potential sources of ignition and situations that may lead to wildfires. Figure 1 illustrates the primary conditions and factors that play a crucial role in determining the risk of forest fires.

Fig. 1

Structural diagram of forest fire risk formation

Identifying and understanding these conditions and factors is essential for effectively assessing and managing the risk of wildfires in forested areas. By addressing these elements comprehensively, it becomes possible to implement measures to eliminate or control the various sources of fire risk, ultimately enhancing fire safety and protection of forested regions.

3.3 Assessment of the Factors in the Detection of a Wildfire

The risk of late detection of wildfires is influenced by various factors. Several elements can hinder the timely detection of fires, including atmospheric phenomena such as clouds, gas pollution, and smoke, as well as terrain features like high altitudes and steep inclines in hillslopes. Additionally, social factors play a role in detecting wildfires. The assistance of pedestrians, workers from different enterprises, and drivers (including those operating vehicles, river vessels, railways, aircraft, etc.) is crucial in identifying emerging fires and communicating this information to relevant fire department personnel.

The effectiveness of a forest fire detection system depends on a combination of organizational and technical factors. These factors include the presence of a territorial control system and the availability of means for transmitting operational information swiftly, all of which contribute to the overall efficiency of the wildfire detection and response efforts.

The wildfire probability detection function relies significantly on ground monitoring, which encompasses various components such as:

• Fire monitoring posts: These are strategically placed locations equipped for monitoring and detecting forest fires.

• Lightning rods: Devices used to capture lightning strikes, as lightning is a common cause of forest fires.

• Television installations: These may include towers, antennas, and other communication equipment that can aid in the detection and reporting of fires.

• Patrolling: Regular patrolling of forested areas using various means, including drones, roads, motor transport, and river vessels, plays a crucial role in monitoring for potential fires.

To assess the probability of detecting a forest fire, coefficients are assigned to each of these factors to indicate their significance. These coefficients influence the overall assessment of the likelihood of detecting a forest fire based on whether these factors are present or absent during the survey of a specific area.

The structural diagram of how risk forms in the context of detecting a forest fire is illustrated in Fig. 2. Diagram providing an overview of the key conditions and factors that contribute to the risk associated with detecting forest fires.

Fig. 2

Structural diagram of risk formation upon detection of a forest fire

3.4 Assessment of the Factors for the Development of Wildfires

When assessing the risk of forest fires, it's crucial to consider not only the possibility of ignition but also the potential for the fire to develop and spread uncontrollably. As a wildfire evolves, its risk level increases significantly. To account for this, the assessment of wildfire risk involves evaluating both the likelihood of a fire starting and the potential for it to escalate and become unmanageable. This comprehensive approach helps in better understanding and managing the risk associated with forest fires. Figure 3 outlines the main conditions and factors that contribute to the risk of forest fires, emphasizing the importance of considering both ignition and fire development in the risk assessment process.

Fig. 3

Structural diagram of forest fire development risk formation

3.5 Assessment of the Factors for Extinguishing Wildfires

In the forest fire risk assessment process, the focus shifts to considering measures aimed at minimizing the consequences of emerging and spreading wildfires. This involves evaluating a combination of physical and organizational measures designed to combat wildfires effectively. Effective wildfire suppression depends on a range of factors falling into categories such as natural, social, technical, and organizational. These factors interact in complex ways to influence the ability to control and extinguish wildfires. Figure 4 illustrates the intricate structure of these key factors involved in wildfire suppression.

Fig. 4

Structural diagram of risk formation when extinguishing a forest fire

Implementing effective measures to protect forests from fires requires a collaborative approach involving various government departments and organizations. This includes cooperation with the Ministry of Interior, Ministry of Agriculture, Forest Executive Agency, departmental fire services, forest fire services, forestry and agricultural enterprises, and tenants. To facilitate this cooperation, it is recommended to establish a plan for interaction with these organizations. The effectiveness of wildfire suppression efforts is also influenced by the entity responsible for the assessed forest area, whether it is owned by the state, municipality, church, scientific organizations, cooperatives, or other entities. Each of these entities may have varying capabilities and resources related to fire safety, making it essential to consider these factors in the assessment process.

3.6 Calculation and Formalization of Forest Fire Risk

The process of conducting a wildfire risk assessment involves several logical steps, with the questionnaire being a central component of this methodology. The developed questionnaire is designed to gather information and assess various factors related to the risk of wildfires. It aims to provide quantitative values for wildfire risk by combining probabilities associated with fire occurrence, development, detection, extinguishing, and the potential consequences of fires.

To ensure the accuracy of the assessment, it is essential to involve not only experts and survey results but also administrative staff, forestry specialists, and other relevant organizations. Additionally, available materials such as statistical data, maps, and forestry records should be utilized during the assessment process. The questionnaire consists of questions grouped by key factors, and each question is designed to produce quantitative or qualitative (yes/no) values that reflect the impact of each indicator. These values are then used for data processing and analysis to calculate the risks associated with fire occurrence, development, detection, extinguishing, and the overall integrated risk for a specific forest area, whether it be a division, subdivision, forest section, or forest enterprise. The risk of occurrence, late detection, development, and extinguishing risks—R_i) is determined by Eq. (4):

$${R}_{i}=\sum_{i=1}^{k}{A}_{ij}{a}_{j}$$

(4)

where a_i—quantitative (qualitative) values of various factors (natural, social, organizational and technical); A_ij is a weighting factor that takes into account the effect of the j-th parameter on the i-th type of fire hazard. The algorithm for calculating the i-th risk is (Eq. 5):

$$ \begin{aligned} R_{i} & = \left( {r_{0} = \sum KO_{i} KL_{i} } \right) \to \left( {r_{i} = \sum R_{0} K2_{i} } \right) \to \left( {r_{2} = \sum r_{1} K3_{i} } \right) \\ & \quad \to \left( {r_{3} = \sum r_{2} K4_{i} } \right) \\ \end{aligned}$$

(5)

where r_i—intermediate values of risks of values, conditions, and factors. The total risk of fire is calculated by Eq. (6):

$${R}_{tot}=\sum {R}_{i}{K5}_{i}$$

(6)

Then, the risks of forest occurrence of fires, development risks, detection, and extinguishing risks and the integrated (total) risk for forest division, subdivision, forest section, or forest enterprise are determined as weighted averages, taking into account the areas of these units and the total calculated area:

$${R}_{S}= \frac{{R1}_{S1}+{R2}_{S2}+\dots +{Rn}_{Sn}}{S}$$

(7)

where R_s—risk (occurrence, development, detection, extinguishing, and integral) for forest subdivision, forest section or forest enterprise; R_n—the similar risk of forest division, subdivision, forest section or forest enterprise; s_n—an area of forest subdivision, forest section or forest enterprise, hectares; S is the total estimated area, hectares.

Depending on the obtained numerical indicators for the risks of wildfires, the range of their possible values is divided into several intervals, each of which corresponds to a certain level of risk according to the accepted world gradation of risks (fire, industrial, etc.). Based on the results of the assessment of the main types of risks of forest fires (occurrence, development of fire, late detection, and unsuccessful extinguishing) for the forest division, subdivision, forest section, or forest enterprise is determined integrated risk assessment of wildfires and the corresponding level (Table 1).

Table 1 Classification values of forest fire risk (FFR)

4 Conclusions

The forest fire risk assessment process concludes with the development of an action plan that includes recommendations for reducing the level of fire risk to a specific limit or maintaining it at an acceptable level. Even if the current level of fire danger is deemed acceptable, these recommendations can facilitate the use of more cost-effective measures for preventing and extinguishing forest fires. The presented methodology for assessing forest fire risk is designed to assist practitioners in accurately evaluating risk at the smallest territorial divisions within forestry, including forest enterprises, forest sections, forest divisions, and subdivisions. It can be easily implemented at various levels of forest management and can contribute to improved risk classification within forestry operations.