Engineering system for prevention, localization and restoration after natural fires
Fire resistance of a mountain ridge is the ability of the territory to:
reduce the risk of ignition;
limit the rate of fire spread;
prevent a ground fire from turning into a crown fire;
maintain escape and access routes;
ensure early detection;
maintain local fire extinguishing;
prevent catastrophic erosion after a fire;
maintain the functionality of the water collection system.
On the ridges, fires are especially dangerous due to a combination of:
strong wind;
low humidity;
thin air;
high solar load;
dry vegetation;
rapid change in wind direction;
difficult access;
limited water supply;
high rate of fire spread along the slope;
transfer of burning particles over long distances.
Fire resistance is not achieved by creating a completely cleared or vegetated area. A bare ridge after clearing loses its protection from wind and water erosion and becomes especially vulnerable after the first heavy rain.
The main principle:
Fire architecture must break the continuity of combustible material, preserve living soil cover and provide controlled corridors for fire, water, equipment and evacuation.
1. Fire as a process of energy transfer
The spread of a natural fire is determined by three main heat transfer mechanisms:
1.1 Thermal radiation
Flames heat vegetation ahead of the fire front.
Under the influence of radiation:
moisture evaporates;
thermal decomposition of organic matter begins;
flammable gases are released;
the fuel temperature approaches the flash point.
Dense shrub areas and continuous crowns increase the radiant load.
1.2. Convection
Hot gases move upward and in the direction of the wind.
On the slope there is a convective flow:
warms the vegetation above the front;
accelerates the upward movement of fire;
carries sparks;
creates local vortices;
changes the direction of the flame.
In strong winds, convection becomes the main accelerator of fire.
1.3. Transfer of burning particles
Sparks, embers, bark, pine needles and small branches are carried by the air flow.
They create:
spot fires ahead of the front;
fire spreading across the road;
fire outside the firebreak;
ignition of roofs and equipment;
multiple independent foci.
Therefore, one cleared strip does not guarantee stopping the fire.
2. Combustible environment of the comb
For engineering analysis, vegetation is considered as a fuel system.
Main parameters:
mass of combustible material;
humidity;
particle size;
vertical structure;
horizontal continuity;
proportion of dry organic matter;
fuel location height;
content of resins and essential oils;
speed of recovery after damage.
3. Classes of vegetable fuel
3.1. Fine fuel
These include:
dry grass;
pine;
leaves;
thin branches;
bark;
mosses in a dry state.
Fine fuel:
dries quickly;
highly flammable;
reacts quickly to the wind;
determines the initial speed of fire spread.
On ridges, it is dry grass that often becomes the main conductor of the fire front.
3.2. Medium fuel
Includes:
shrub branches;
young trunks;
medium diameter wood debris;
dense dry vegetation.
It burns longer and releases more energy.
3.3 Large fuel
These include:
trunks;
stumps;
large branches;
raindrop;
dead trees.
Large wood does not always ignite easily, but once ignited:
retains heat for a long time;
creates smoldering fires;
damages roots;
may re-ignite;
becomes a source of coals.
3.4 Underground fuel
These include:
peat;
thick humus;
dry roots;
organic layers;
wood under the soil.
Underground combustion may continue after the open flame has disappeared.
Particularly dangerous are:
peat areas;
old root systems;
deep forest floor;
dry organic pockets between rocks.
4. Vertical continuity of fuel
The transition from a ground fire to a crown fire occurs through so-called ladder fuel.
The sequence might look like this:
dry grass → low shrubs → tall shrubs → lower branches → tree crown
To break this chain it is necessary:
remove dry grass under dense bushes;
maintain distance between bushes and tree crowns;
remove dead lower branches;
limit the accumulation of dead wood;
separate tall shrubs and trees;
maintain a moist, low cover.
Simply thinning trees without working the understory can increase wind speeds at the surface and intensify ground fires.
5. Horizontal continuity of fuel
Continuous vegetation allows the fire to move without interruption.
To reduce continuity, a mosaic is created:
low-grass areas;
shrub islands;
forest groups;
stone surfaces;
wet areas;
roads;
technical firebreaks;
managed grazing areas.
Gaps must be functionally connected. Random, small gaps between plants do not form a reliable fire protection system.
6. Types of fires
6.1 Grass Fire
Characterized by:
high speed;
relatively short duration;
strong dependence on wind;
the ability to quickly move over the ridge.
The danger lies in quickly reaching the bushes and forest edge.
6.2. Ground forest fire
They burn:
bedding;
grass;
shrubs;
lower branches;
rainstorm.
It can damage the roots and bases of trees even without moving into the crown.
6.3. Crown fire
The fire spreads through the tree crowns.
Basic conditions:
dense forest structure;
availability of ladder fuel;
dry crowns;
strong wind;
steep slope.
A crown fire is characterized by high intensity and difficulty of direct extinguishing.
6.4. Underground fire
Peat, roots and organic soil burn.
He can:
spread unnoticed;
emerge to the surface in new places;
survive after rain;
weaken the roots of trees;
create failures.
6.5. Combined fire
On complex mountainous terrain, ground, crown and underground types of combustion can occur simultaneously.
7. Influence of relief
7.1. Slope steepness
Fire spreads faster upslope because:
the flame leans towards the fuel;
convective flow heats the vegetation above;
sparks rise up the slope;
the distance between the flame and the fuel decreases.
The steeper the slope, the more difficult direct fire extinguishing and evacuation are.
7.2. Comb
On the ridge the following are possible:
wind acceleration;
sudden change of direction;
transfer of fire to the adjacent slope;
vortex formation;
rupture of the convective column;
multiple point foci.
The ridge cannot automatically be considered a natural fire stop line.
7.3. Saddle
The saddle can act as an aerodynamic nozzle.
Here we observe:
increased gusts;
flame acceleration;
coal transfer;
quick transition between pools.
Saddles are considered areas of high fire risk.
7.4. Gorge and hollow
Narrow landforms can act as a chimney.
Fire and hot air:
concentrate;
accelerate upward;
create powerful convection;
make evacuation difficult.
It is dangerous to place fire shelters and main evacuation routes in such depressions.
8. Wind scenarios
The fire model must take into account more than just the average wind.
Required scenarios:
constant background wind;
seasonal dry wind;
thunderstorm squall;
downward flow;
fawn;
abrupt change of direction;
gusty wind in the saddle;
night runoff of cold air;
wind after the front passes;
convective wind of the fire itself.
A large fire can independently change local air circulation.
9. Fire safety architecture design zones
Zone A. Low protective surface
It is located directly on the line of the most likely arrival of fire.
Consists of:
low grasses;
stone mulch;
sparse vegetation;
managed grazing areas;
stable turf.
The task is to reduce the flame length and the intensity of the lower front.
Zone B. Bush fuel rupture
In this zone:
bushes are placed in separate groups;
dry mass is removed;
a continuous wall of shrubs is excluded;
passages for equipment and water are maintained.
Zone C. Sparse tree layer
Trees:
divided by crowns;
have a cleaned lower part of the barrel;
do not connect with bushes;
represented by different ages and species;
do not create a continuous top line.
Zone D. Inner Protected Area
Includes:
wet plantings;
fire tanks;
turning areas;
monitoring stations;
safe zones;
engineering structures.
10. Fire breaks
A firebreak is a strip of reduced flammability, not necessarily a completely vegetation-free surface.
Types of breaks:
mineralized strip;
low grass strip;
pasture strip;
road;
stone zone;
damp hollow;
a wide strip of sparse forest;
combined corridor.
The width is determined by:
vegetation height;
the length of the expected flame;
slope;
wind direction;
possible transfer of coals;
availability of extinguishing;
the purpose of the protected object.
The narrow line does not protect against the transfer of burning particles.
11. Mineralized stripes
The mineralized strip is created by removing combustible organic material down to the mineral soil.
Applies to:
around critical infrastructure;
along individual roads;
around tanks;
near fire sites;
when localizing an active fire.
Flaws:
risk of erosion;
rapid overgrowth;
need for maintenance;
transformation into a surface runoff channel;
disturbance of soil biota.
On slopes, the strip should not be laid directly along the line of maximum slope without drainage.
12. Fire-resistant vegetation strips
Such stripes consist of species with relatively:
high tissue humidity;
low resin content;
slow accumulation of dry mass;
open crown structure;
the ability to recover quickly;
low altitude.
However, there are practically no completely non-flammable plants.
Even moisture-loving vegetation can become fuel during prolonged drought.
13. Mosaic vegetation management
The optimal comb structure includes:
alternation of open and closed areas;
groups of different ages;
gaps between bushes;
local wet zones;
limited woody islands;
areas with low flammability;
accessible fire corridors.
The mosaic reduces the likelihood of the entire area synchronously transitioning to intense combustion.
14. Dry biomass management
Basic operations:
seasonal mowing;
controlled grazing;
crushing;
removal of dry branches;
wood processing;
creating controlled piles outside the paths of fire and water;
limited controlled burning by specialists;
maintaining gaps.
The cut dry mass must not be left in a continuous layer on the surface.
Shredded wood also remains a combustible material and, if thick, can smolder for a long time.
15. Deadwood and brushwood
Dead wood is important for the ecosystem, but its placement must be managed.
It is permissible to save:
individual large trunks;
wood in persistently damp places;
limited ecological areas;
material outside fire corridors.
Wood must be removed or redistributed:
near roads;
under communication lines;
in saddles;
around buildings;
in emergency channels;
under dense crowns;
in places where burning logs may roll down.
16. Rolling burning materials
On steep slopes burning:
branches;
cones;
log;
stones with burning organic matter
can roll down and create new foci.
The following is provided:
transverse stone barriers;
catchment areas;
clearing slopes above roads and buildings;
absence of timber storage facilities on the slope;
safe material stopping zones.
17. Managed grazing
Grazing can reduce the mass of grass fuel.
But if used incorrectly it:
destroys turf;
compacts the soil;
creates trails;
increases erosion;
destroys young vegetation.
It is necessary to regulate:
animal density;
season;
duration;
residual grass height;
access to wet areas;
location of watering places.
18. Controlled burning
Controlled fire may be used to reduce accumulated fuel only if:
approved plan;
qualified team;
weather window;
safe borders;
reserve forces;
wind forecast;
fuel moisture control;
termination plan;
follow-up observation.
On windy ridges the window of safe use is extremely limited.
Unauthorized burning is unacceptable.
19. Roads as fire infrastructure
The ridge road can perform the following functions:
access for fire-fighting equipment;
evacuation route;
observation lines;
fire break;
turning areas;
hose routing lines.
For this, the road must have:
sufficient load-bearing capacity;
safe width;
traveling pockets;
turning areas;
designated dead ends;
protection against falling trees;
stable water drainage;
backup exit.
A single exit road should not be considered a safe evacuation route.
20. Dead-end routes
For each dead end the following are determined:
maximum length;
turning area;
temporary security zone;
connection;
pointers;
emergency pedestrian exit;
lack of dense fuel around.
During a severe fire, a dead-end road can become a trap.
21. Fire safety platforms
The site must:
have a minimal thermal load;
be free of tall trees;
have a low flammable cover;
have two exit directions;
do not be in a hollow;
do not be located under a rocky cliff;
do not be in the path of smoke;
have a connection;
be designated.
The safety area does not replace evacuation.
22. Water supply for extinguishing
Distributed storage of water is necessary on the ridges.
Sources:
closed tanks;
fog water storage tanks;
rainwater tanks;
fire ponds below the ridge;
technical containers;
mobile tanks;
accumulation of overflow discharge of springs.
The system must take into account:
seasonal minimum occupancy;
freezing;
evaporation;
pollution;
technical access;
connection type;
static pressure;
backup power supply for pumps.
23. Placement of fire tanks
The tanks are located:
outside the fall zone of large trees;
outside the emergency watercourse;
outside the landslide area;
below the most wind-dangerous line;
next to the road;
with the possibility of gravity feed;
with protection against direct heating.
One large tank is less reliable than several distributed tanks.
24. Hydraulic network
For key objects, a network can be created:
tank;
highway;
sectional valves;
fire hydrants;
connection points;
drainage valves;
pumping station;
backup power supply.
The system is designed so that damage to one section does not shut down the entire network.
25. Stationary irrigation systems
The following are permitted around particularly important objects:
sprinklers;
water curtains;
roof humidification systems;
remotely controlled injectors.
Limitations:
high water consumption;
food addiction;
wind exposure;
clogging of injectors;
freezing;
low efficiency under extreme heat flow.
This system is an additional, not a primary protection.
26. Early detection
The monitoring system includes:
optical cameras;
thermal imagers;
smoke detectors;
infrared satellite data;
drones;
weather stations;
lightning sensors;
acoustic sensors;
observer reports.
On the ridge, cameras with a view of several slopes are especially important.
27. Meteorological monitoring
Controlled by:
air temperature;
relative humidity;
wind speed;
gusts;
direction;
amount of precipitation;
fuel moisture;
soil moisture;
duration of drought;
lightning activity.
Wind data should be taken directly on the ridge, and not just in the valley.
28. Fuel moisture
Fire hazard is determined by humidity:
dry grass;
bedding;
small branches;
shrubs;
living vegetation;
large timber.
Small fuel reacts to weather changes much faster than large wood.
After a short rain, the grass can quickly dry out again in a strong wind.
29. DREVO Fire Risk Digital Twin
The digital twin fire module contains:
relief;
plant communities;
type and weight of fuel;
humidity;
roads;
reservoirs;
wind direction;
potential ignition points;
power lines;
tourist areas;
evacuation routes;
fire breaks;
historical fires;
soil condition;
fire spread forecast.
The model should show:
possible direction of the front;
speed of propagation;
probability of transition to crowns;
coal transfer;
time to reach objects;
available routes;
dangerous dead ends;
required localization points.
30. Sources of ignition
The following are analyzed:
lightning;
bonfires;
smoking;
transport;
agricultural work;
power lines;
construction equipment;
sparks from brakes and metal;
intentional arson;
controlled burning;
power plants.
For each source, technical and organizational limitations are determined.
31. Lightning protection and thunderstorm fires
After a dry thunderstorm it is necessary:
analyze the discharge map;
perform a thermal imaging flyby;
check dry trees;
observe hidden foci;
control peat and root areas.
Lightning fires can occur long after the thunderstorm itself.
32. Power lines
Risks:
contact of branches with wires;
fall of supports;
broken wires;
sparking;
equipment overheating;
ignition of dry vegetation.
Required:
clearing the adjustable corridor;
tree control;
automatic shutdown of the damaged section;
wind monitoring;
fire-resistant bases;
access for repairs.
33. Communication and autonomy
In case of fire the following is possible:
power outage;
damage to the mobile network;
loss of internet connection;
road blocking.
Required:
backup radio channels;
autonomous repeaters;
local sirens;
satellite communications for key points;
battery powered;
local data recording;
manual plans and maps.
34. Operational zoning
Green zone
Low current danger, normal mode.
Yellow zone
Increased dryness, limitation of fire work.
Orange zone
High probability of rapid spread, closure of individual routes.
Red Zone
Extreme fire weather, access restrictions, evacuation preparedness.
Black Zone
Active uncontrolled fire or loss of access and communication.
35. Evacuation
The evacuation plan must take into account:
fire spread rate;
smoke direction;
wind change;
road capacity;
oncoming traffic of equipment;
falling trees;
decreased visibility;
coal transfer;
blocking the main route.
Minimum required:
main route;
backup route;
safe area;
warning system;
responsible persons;
map of closed areas.
36. Smoke behavior
Smoke can:
climb a slope;
descend at night;
accumulate in saddles;
obscure the view;
block the road;
create a hazard far from the fire.
An evacuation route cannot be designed solely based on the expected movement of the flame.
37. Protection of water collection structures
Fire can damage:
plastic pipes;
sensors;
cables;
reservoirs;
mist eliminators;
wooden structures;
filters;
waterproofing.
Critical elements must have:
non-flammable protection;
deepening;
distance from fuel;
sectioning;
backup lines;
mechanical valves;
access after fire.
38. Impact of fire on soil
Temperature exposure can cause:
death of soil biota;
destruction of organic matter;
loss of structure;
formation of a water-repellent layer;
reduction of infiltration;
increase in surface runoff;
increased erosion.
A hydrophobic layer sometimes forms below the surface, creating a hidden boundary along which water moves quickly downslope.
39. Post-fire flood risk
After a fire, a watershed can produce significantly faster and more polluted runoff.
Reasons:
absence of plant interception;
reduction of roughness;
root damage;
soil hydrophobicity;
presence of ash;
a large amount of loose material;
clogging of riverbeds with wood.
The first heavy rainfall after a fire is often more dangerous than the rain itself in undamaged areas.
40. Post-fire mudflow risk
On steep slopes, a flow can form from:
water;
ash;
soils;
stones;
roots;
burnt trunks.
Particularly dangerous are:
upper troughs;
rocky couloirs;
road dumps;
burnt shrubby slopes;
areas above populated areas.
41. Primary stabilization after a fire
Priorities:
safety assessment;
identification of slopes with mudflow hazard;
restoration of emergency waterways;
protection of roads and bridges;
securing the most active gullies;
protection of springs;
removal of dangerous tree blockages;
rain monitoring;
access restriction;
restoration of soil cover.
42. Anti-erosion measures after a fire
Applicable:
fixed mulch;
tree shafts along the contour;
low stone lines;
biodegradable mats;
sowing of local grasses;
protection of riverbeds;
sediment traps;
sectional road restoration.
Measures should not:
block the emergency drain;
form large tree dams;
direct water to one point;
introduce invasive species.
43. Emergency trees
After a fire, trees may remain upright, but may have damage:
roots;
reason;
trunk;
internal structure;
crown.
They are especially dangerous:
near roads;
near communication lines;
around tanks;
above the paths;
on windy ridges;
on saturated soil.
Removal is carried out based on risk assessment rather than through complete clearing.
44. Vegetation restoration
Subsequence:
Stage 1. Soil protection
Reduced erosion and preservation of surviving roots.
Stage 2. Natural regeneration
Assessing the ability of native species to recover on their own.
Step 3: Invasive Species Control
Disturbed areas are particularly vulnerable to invasion by alien plants.
Step 4: Overseeding with native grasses
Only where natural restoration is insufficient.
Stage 5. Shrub layer
It is restored in a mosaic manner, without forming a continuous combustible wall.
Stage 6. Arboreal layer
It is being returned gradually, taking into account the future fire structure.
45. Fire-resistant restoration
It is not possible to automatically return an area to its previous state if the previous structure contributed to a catastrophic fire.
It is necessary to adjust:
density;
age structure;
distances between crowns;
amount of dry biomass;
arrangement of shrubs;
fire corridors;
technical access;
water supply;
monitoring system.
46. Maintenance
The following are performed regularly:
mowing;
removing dry grass;
pruning lower branches;
shrub control;
road cleaning;
tank inspection;
hydrant testing;
radio communication check;
camera maintenance;
control of power lines;
fuel map update;
checking evacuation routes.
47. Frequency of inspections
Every year before the fire season
Full technical audit.
After a strong wind
Monitoring for falls, breakdowns and new fuel blockages.
After the drought
Re-evaluation of moisture and dry biomass.
After the storm
Checking for possible lightning sources.
After the fire
Geotechnical and hydrological assessment.
After the first heavy rain
Checking erosion, mudflows and drainage systems.
48. Fire resistance indicators
Key indicators:
mass of fine dry fuel;
continuity of grass cover;
distance between shrub groups;
vertical gap between shrubs and crowns;
distance between crowns;
volume of available water;
detection time;
arrival time;
number of independent routes;
communication functionality;
share of territory covered by monitoring;
area of soil protected after fire;
probability of post-fire mudflow.
49. What not to do
It is forbidden:
create continuous even-aged plantings;
plant a dense line of conifers along the ridge;
consider the road as a sufficient fire break;
leave the cut dry mass in place;
lay mineralized strips without drainage;
place one tank without redundancy;
design one evacuation route;
rely only on mobile communications;
leave dead wood in fire corridors;
completely clear the ridge down to bare soil;
ignore the transfer of coals;
restore the original combustible structure after a fire;
postpone hydrological stabilization until next season.
50. Design sequence
Stage 1. Fuel mapping
The type, mass, moisture content and continuity of vegetation are determined.
Stage 2. Relief analysis
Ridges, saddles, hollows and fire acceleration zones are identified.
Stage 3. Wind modeling
Normal and extreme directions are considered.
Stage 4. Distribution scenarios
Grass, ground, crown, underground and combined fires.
Stage 5. Mosaic design
Gaps, low-combustibility zones and fire corridors are created.
Stage 6. Infrastructure
Roads, sites, tanks, hydrants, communications and sensors.
Stage 7. Evacuation
Primary and secondary routes, safe areas and alerts.
Stage 8. Post-fire scenario
Erosion, flooding, mudflow and spring restoration.
Step 9. Maintenance
Fixed work schedule and responsible operators.
Step 10. Model adjustment
After every fire, strong wind and extreme rainfall.
The final principle
The fire resistance of a ridge is not determined by a single firebreak, but by a combination of interconnected solutions:
controlled fuel structure;
mosaic vegetation;
break in vertical and horizontal continuity;
access to equipment;
distributed water supply;
early detection;
backup communication;
safe evacuation;
protection of emergency waterways;
rapid post-fire restoration of soil.
A fire-resistant ridge is an area where the fire does not receive continuous fuel, fire services maintain access, and the first rainfall after a fire does not turn the burned slope into a source of flooding and mudflows.