77 research outputs found
A review of wildland fire spread modelling, 1990-present 3: Mathematical analogues and simulation models
In recent years, advances in computational power and spatial data analysis
(GIS, remote sensing, etc) have led to an increase in attempts to model the
spread and behvaiour of wildland fires across the landscape. This series of
review papers endeavours to critically and comprehensively review all types of
surface fire spread models developed since 1990. This paper reviews models of a
simulation or mathematical analogue nature. Most simulation models are
implementations of existing empirical or quasi-empirical models and their
primary function is to convert these generally one dimensional models to two
dimensions and then propagate a fire perimeter across a modelled landscape.
Mathematical analogue models are those that are based on some mathematical
conceit (rather than a physical representation of fire spread) that
coincidentally simulates the spread of fire. Other papers in the series review
models of an physical or quasi-physical nature and empirical or quasi-empirical
nature. Many models are extensions or refinements of models developed before
1990. Where this is the case, these models are also discussed but much less
comprehensively.Comment: 20 pages + 9 pages references + 1 page figures. Submitted to the
International Journal of Wildland Fir
Cellular automata simulations of field scale flaming and smouldering wildfires in peatlands
In peatland wildfires, flaming vegetation can initiate a smouldering fire by
igniting the peat underneath, thus, creating a positive feedback to climate change by
releasing the carbon that cannot be reabsorbed by the ecosystem. Currently, there are
very few models of peatland wildfires at the field-scale, hindering the development of
effective mitigation strategies. This lack of models is mainly caused by the complexity of
the phenomena, which involves 3-D spread and km-scale domains, and the very large
computational resources required. This thesis aims to understand field-scale peatland
wildfires, considering flaming and smouldering, via cellular automata, discrete models
that use simple rules. Five multidimensional models were developed: two laboratory-scale
models for smouldering, BARA and BARAPPY, and three field-scale models for flaming
and smouldering, KAPAS, KAPAS II, and SUBALI. The models were validated against
laboratory experiments and field data. BARA accurately simulates smouldering of peat
with realistic moisture distributions and predicts the formation of unburned patches.
BARAPPY brings physics into BARA and predicts the depth of burn profile, but needs 240
times more computational resources. KAPAS showed that the smouldering burnt area
decreases exponentially with higher peat moisture content. KAPAS II integrates daily
temporal variation of moisture content, and revealed that the omission of this temporal
variation significantly underestimates the smouldering burnt area in the long term.
SUBALI, the ultimate model of the thesis, integrates KAPAS II with BARA and considers the ground water table to predict the carbon emission of peatland wildfires. Applying
SUBALI to Indonesia, it predicts that in El Niño years, 0.40 Gt-C in 2015 (literature said
0.23 to 0.51 Gt-C) and 0.16 Gt-C in 2019 were released, and 75% of the emission is from
smouldering. This thesis provides knowledge and models to understand the spread of
flaming and smouldering wildfires in peatlands, which can contribute to efforts to
minimise the negative impacts of peatland wildfires on people and the environment,
through faster-than-real-time simulations, to find the optimum firefighting strategy and
to assess the vulnerability of peatland in the event of wildfires.Open Acces
Forest fire spreading: a nonlinear stochastic model continuous in space and time
Forest fire spreading is a complex phenomenon characterized by a stochastic
behavior. Nowadays, the enormous quantity of georeferenced data and the
availability of powerful techniques for their analysis can provide a very
careful picture of forest fires opening the way to more realistic models. We
propose a stochastic spreading model continuous in space and time that is able
to use such data in their full power. The state of the forest fire is described
by the subprobability densities of the green trees and of the trees on fire
that can be estimated thanks to data coming from satellites and earth
detectors. The fire dynamics is encoded into a density probability kernel which
can take into account wind conditions, land slope, spotting phenomena and so
on, bringing to a system of integro-differential equations for the probability
densities. Existence and uniqueness of the solutions is proved by using
Banach's fixed point theorem. The asymptotic behavior of the model is analyzed
as well. Stochastic models based on cellular automata can be considered as
particular cases of the present model from which they can be derived by space
and/or time discretization. Suggesting a particular structure for the kernel,
we obtain numerical simulations of the fire spreading under different
conditions. For example, in the case of a forest fire evolving towards a river,
the simulations show that the probability density of the trees on fire is
different from zero beyond the river due to the spotting phenomenon.
Firefighters interventions and weather changes can be easily introduced into
the model.Comment: 25 pages, 27 figure
Monitoring and Cordoning Wildfires with an Autonomous Swarm of Unmanned Aerial Vehicles
Unmanned aerial vehicles, or drones, are already an integral part of the equipment used by firefighters to monitor wildfires. They are, however, still typically used only as remotely operated, mobile sensing platforms under direct real-time control of a human pilot. Meanwhile, a substantial body of literature exists that emphasises the potential of autonomous drone swarms in various situational awareness missions, including in the context of environmental protection. In this paper, we present the results of a systematic investigation by means of numerical methods i.e., Monte Carlo simulation. We report our insights into the influence of key parameters such as fire propagation dynamics, surface area under observation and swarm size over the performance of an autonomous drone force operating without human supervision. We limit the use of drones to perform passive sensing operations with the goal to provide real-time situational awareness to the fire fighters on the ground. Therefore, the objective is defined as being able to locate, and then establish a continuous perimeter (cordon) around, a simulated fire event to provide live data feeds such as e.g., video or infra-red. Special emphasis was put on exclusively using simple, robust and realistically implementable distributed decision functions capable of supporting the self-organisation of the swarm in the pursuit of the collective goal. Our results confirm the presence of strong nonlinear effects in the interaction between the aforementioned parameters, which can be closely approximated using an empirical law. These findings could inform the mobilisation of adequate resources on a case-by-case basis, depending on known mission characteristics and acceptable odds (chances of success)
A multi-scale network with percolation model to describe the spreading of forest fires
Forest fires have been a major threat to forest ecosystems and its biodiversity, as well as the environment in general, particularly in the Mediterranean regions. To mitigate fire spreading, this study aims at finding a fire-break solution for territories prone to fire occurrence. To the effect, here follows a model to map and predict phase transitions in fire regimes (spanning fires vs. penetrating fires) based on terrain morphology. The structure consists of a 2-scale network using site percolation and SIR epidemiology rules in a cellular automata to model local fire Dynamics. The target area for the application is the region of Serra de Ossa in Portugal, due to its wildfire incidence. The study considers the cases for a Moore neighbourhood of warm cells of radius 1 and 2 and also considers a heterogeneous terrain with 3 classes of vegetation. Phase transitions are found for different combinations of fire risk for each of these classes and use these values to parametrize the resulting landscape network.info:eu-repo/semantics/publishedVersio
Modeling the risk of invasion and spread of Tuta absoluta in Africa
Tuta absoluta is an invasive insect that originated from South America and has spread to Europe Africa and Asia. Since its detection in Spain in 2006, the pest is continuing to expand its geographical range, including the recent detection in several Sub-Saharan African countries. The present study proposed a model based on cellular automata to predict year-to-year the risk of the invasion and spread of T. absoluta across Africa. Using, land vegetation cover, temperature, relative humidity and yield of tomato production as key driving factors, we were able to mimic the spreading behavior of the pest, and to understand the role that each of these factors play in the process of propagation of invasion. Simulations by inferring the pest’s natural ability to fly long distance revealed that T. absoluta could reach South of Africa ten years after being detected in Spain (Europe). Findings also reveal that relative humidity and the presence of T. absoluta host plants are important factors for improving the accuracy of the prediction. The study aims to inform stakeholders in plant health, plant quarantine, and pest management on the risks that T. absoluta may cause at local, regional and event global scales. It is suggested that adequate measures should be put in place to stop, control and contain the process used by this pest to expand its range
Using cellular automata to simulate wildfire propagation and to assist in fire management
Cellular automata have been successfully applied to simulate the propagation
of wildfires with the aim of assisting fire managers in defining fire
suppression tactics and in planning fire risk management policies. We present
a cellular automaton designed to simulate a severe wildfire episode that took
place in Algarve (southern Portugal) in July 2012. During the episode almost
25 000 ha burned and there was an explosive stage between 25Â and 33 h
after the onset. Results obtained show that the explosive stage is adequately
modeled when introducing a wind propagation rule in which fire is allowed to
spread to nonadjacent cells depending on wind speed. When this rule is
introduced, deviations in modeled time of burning (from estimated time based
on hot spots detected from satellite) have a root-mean-square difference
of 7.1 for a simulation period of 46 h (i.e., less than 20 %). The
simulated pattern of probabilities of burning as estimated from an ensemble
of 100Â simulations shows a marked decrease out of the limits of the observed
scar, indicating that the model represents an added value to help decide locations of
where to allocate resources for fire fighting.</p
Development of a Model for Mitigating Fire Spread in Multi-Storey Buildings
In the developing nations that are located in the tropical region; there is a growing trend of fire incidence in buildings without adequate development of fire prevention and/or reduction protocol. Thus, this study addresses the growth and spread of fire in multi-storey buildings. The rooms are structured as cells in order to reduce the flame spread from a single fuel item, by heat release, to other neighbouring items or rooms (otherwise known as cells). The philosophy is to reduce the advent of vertical and horizontal fire spread. Thus, the mathematical model for the spread of fire in buildings over a solid fuel surface is therefore developed using the adaptation, development and simulation of cellular automata (CA) discrete model. The von Neumann neighbourhood cell configuration is adopted. Hence, the surface of the fuel is analysed using a regular square array (i.e. cells), while the flame spread is depicted as a series of ignitions of surface elements. In which case, ignition of an element is evaluated by a combination of critical surface ignition temperature and cellular automata discrete techniques. The work displays the movement of fire, from its origin of ignition to other fuel igniting elements around it. Consequently, this spread to other parts of the building. However, the technique presented in this work attempts to reduce the rate of growth of the fire spread using the predictive fire growth probability approach. In other words, the application of the cellular automata, using a multi-storey building, is herein presented. The study has potential to advance knowledge of technical approach to stop fire spread in multi-storey building. Thus it improves fire risk management as well as reducing magnitude of fire disaster and losses in the multi-storey buildings
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