Technical methods of preventing and limiting the effects of natural disasters caused by severe weather conditions in Polish forests

Abstract

Climate change observed in recent years has led to a rise in the frequency and magnitude of meteorological phenomena such as violent storms, intense rainfall or heat events, which have triggered floods, mass land movement, droughts, and wildfire. The intensification of severe weather conditions has put a strain on forest stand regions in Europe. Weather-related stressors are considered the leading factor in the degradation of forest stands and the growing susceptibility of trees to pathogenic agents. The new dynamic situation has substantially altered the external conditions of forest management in Poland. Long-established management methods have had to be revised, and new approaches developed to face the emerging or aggravated threats to forests. It has become apparent in many cases that sole silvicultural techniques will not be sufficiently effective and should be supported or supplemented by technical solutions to respond adequately. We discuss our research and findings in the domain of engineering solutions applied in forests to optimise the road network, limit the effects of natural hazards, implement hydrological restoration, alter water storage and assess the impact of engineering infrastructure on the environment. The article presents the management of natural hazards and adopted engineering approaches from a Polish perspective. Case studies of applied solutions to prevent and limit the damaging effects of natural hazards and disasters on forests are included. Climate change observed in recent years has led to a rise in the frequency and magnitude of meteorological phenomena such as violent storms, intense rainfall or extreme heat events, which have triggered floods, mass land movements, droughts and wildfires. The intensification of severe weather conditions has put a strain on forest stands in many regions of Europe. Weather-related stressors are considered a leading factor in the degradation of forest stands and the growing susceptibility of trees to pathogenic agents. The new dynamic situation has substantially altered conditions for forest management in Poland. Long-established management methods have had to be revised, while new approaches need to be developed to face the emerging or aggravated threats to forests. It has become apparent in many cases that silvicultural techniques alone will not be sufficiently effective and thus should be supported or supplemented by technical solutions to respond adequately to the altered conditions. This study and the obtained findings are discussed in terms of engineering solutions applied in forests to optimise the road network, limit the effects of natural hazards, implement hydrological restoration and enhance water storage. The article presents management of natural hazards and adopted engineering approaches from a Polish perspective. Case studies of applied solutions to prevent and limit the damaging effects of natural hazards and disasters on forests are included.

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ORIGINAL PAPER
www.forestry.actapol.net
pISSN 1644-0722 eISSN 2450-7997
Acta Sci. Pol.
Silv. Colendar. Ratio Ind. Lignar. 20(4) 2021, 273–286
POLISH JOURNAL OF FORESTRY
bernard.okonski@up.poznan.pl, https://orcid.org/0000-0002-0457-4744
Received: 30.11.2021
Accepted: 27.12.2021
TECHNICAL METHODS OF PREVENTING
AND LIMITING THEEFFECTS OF NATURAL DISASTERS CAUSED
BY SEVERE WEATHER CONDITIONS IN POLISH FORESTS
Andrzej Czerniak, Bernard Okoński, Sylwester M. Grajewski, Ewa E. Kurowska,
Anna Krysztofiak-Kaniewska, Adrian Kasztelan
Department of Forest Engineering, Poznań University of Life Sciences
Wojska Polskiego 71C, 60-625 Poznań, Poland
ABSTRACT
Climate change observed in recent years has led to a rise in the frequency and magnitude of meteorological
phenomena such as violent storms, intense rainfall or extreme heat events, which have triggered oods, mass
land movements, droughts and wildres. The intensication of severe weather conditions has put a strain
on forest stands in many regions of Europe. Weather-related stressors are considered a leading factor in the
degradation of forest stands and the growing susceptibility of trees to pathogenic agents. The new dynamic
situation has substantially altered conditions for forest management in Poland. Long-established manage-
ment methods have had to be revised, while new approaches need to be developed to face the emerging or
aggravated threats to forests. It has become apparent in many cases that silvicultural techniques alone will
not be suciently eective and thus should be supported or supplemented by technical solutions to respond
adequately to the altered conditions. This study and the obtained ndings are discussed in terms of engineer-
ing solutions applied in forests to optimise the road network, limit the eects of natural hazards, implement
hydrological restoration and enhance water storage. The article presents management of natural hazards and
adopted engineering approaches from a Polish perspective. Case studies of applied solutions to prevent and
limit the damaging eects of natural hazards and disasters on forests are included.
Keywords: engineering solutions, extreme weather events, forest protection, limiting forest damage
EFFECTS OF SEVERE WEATHER
ON POLISH FORESTS – INTRODUCTION
Water management – drought and flooding
Forests in Poland contribute largely to biodiversity,
but are under growing pressure from the eects of
climatic hazards due to climate instability (Jabłoński,
2019; Jabłoński et al., 2013). Decreasing water re-
sources require more accurate storage monitoring and
implementation of eective hydrological restoration
projects and application of dedicated engineering so-
lutions. While water resources of Poland are among
the poorest in Europe, water conditions are vital for
the growth and development of tree stands and sus-
taining forest habitats. A large share of water balance
inputs in Poland is used by forest vegetation that cov-
ers almost a third of Polish territory.
In recent years Polish winters have become milder.
While the share of snow storage in the water balance
has reduced, droughts often occur in early spring,
with the very onset of the growing period. Rising
http://dx.doi.org/10.17306/J.AFW.2021.4.26

Czerniak, A., Okoński, B., Grajewski, S. M., Kurowska, E. E., Krysztofiak-Kaniewska, A., Kasztelan, A. (2021). Technical methods of
preventing and limiting the effects of natural disasters caused by severe weather conditions in Polish forests. Acta Sci. Pol. Silv.
Colendar. Ratio Ind. Lignar., 20(4), 273–286. http://dx.doi.org/10.17306/J.AFW.2021.4.26
274 www.forestry.actapol.net/
temperatures, higher evapotranspiration totals and ex-
tended warm periods increase the risk of drought dam-
age to the forest during the vegetation period. In order
to limit the consequences of unstable water availabil-
ity for forest vegetation, numerous projects of local
water storage and hydrological restoration are being
implemented in state-owned forests in Poland. These
involve constructing dams, medium and large reser-
voirs and larger-scale hydrologic restoration projects
made by basin managing authorities and other parties.
The frequency and intensity of oods and the total
area endangered by oodwater have increased in Eu-
rope since the end of the nineteenth century (Paprotny
et al., 2018). It is estimated that about 40% of indus-
trial losses resulting from natural disasters have been
caused by oods (Poprawa and Rączkowski, 2003).
High variability and decreasing stability of river ow
regimes, and thus the growing intensity of extreme
hydrological events, increases the impact of oods as
an ecological stressor for forests (Arnell, 1994; Han-
nah et al., 2006; Mikac et al., 2018; Stahl et al., 2010).
Over the last 30 years there have been numerous ood
events in valleys of medium and large rivers in Poland.
These events often occurred locally and only covered
some sections of river valleys. However, in 1997 and
2010 long-term river ooding occurred in the entire
basin of the Oder and the Vistula of south Baltic and
aected valleys of many medium and large rivers in
the area (Grela et al., 1999; Maciejewski et al., 2011a;
2011b). The 1997 ood resulted in prolonged sur-
face oodwater stagnation and sub-surface waterlog-
ging, and in consequence deterioration of forest stand
growth on active terraces.
Due to usually favourable growth conditions, the
high fertility of valley habitats and good access to wa-
ter the uvial terraces are attractive sites for growing
trees of high commercial value (Okoński, 2019). For-
estry practices favouring those locations are related
with good natural growth in the valleys of such species
as pedunculate oak and European ash, whereas other
tree species that do not occur naturally in river valleys
are also included. A good example in this respect is
provided by Scots pine, which grows well in sandy
soils of valley oors in Central Europe (Danielewicz,
2008). Generally, there is a preference towards tree
species that tolerate changeable and periodically shal-
low sub-surface water levels and exhibit resistance
to the impact of river ooding. Management of com-
mercial tree stands in river valleys needs to consider
ooding damage hazards (Kozlowski, 2002). Numer-
ous factors modify tree resistance to oodwater. The
main factors are connected with species tolerance of
anaerobic conditions caused by stagnant water and en-
vironmental characteristics of river regimes, especial-
ly the frequency, magnitude, annual distribution and
duration of ooding, local physiographic and habitat
conditions, mainly the shape of the river valley and
landforms, soil layer permeability in the river valley
bottom, etc. (Glenz et al., 2006).
Forest fire
While Polish forests are exposed to a moderate wild-
re risk (Szczygieł, 2012), they are considered among
the most ammable in Central Europe (Dobrowolska,
2008). In the case of most individual re events in Po-
land forest res usually consume relatively small ar-
eas (Szczygieł, 2012). The average annual number of
forest res in Poland is 8,500, leading to over 7,000
ha being burnt (Grajewski et al., 2019). The most
remarkable re events occurred in Polish forests in
1992, where 9,000 ha of forest was burnt in the Rudy
Raciborskie Forest Unit and almost 6,000 ha in the
Potrzebowice Forest Unit. In both cases the re was
initiated by jammed train brakes. Unlike some other
European countries, in Poland the rising number of
forest res or the increasing average burnt area have
not been conrmed to be linked to climate change. The
high eciency of the re protection and control sys-
tem employed in Polish forests is viewed as a decisive
factor resulting in these favourable statistics (Grajew-
ski, 2017a; 2017b).
Prevention and limitation of re damage can be
achieved by introducing rebreaks in locations im-
portant for forest protection, coupled with early de-
tection systems and proper access to burning areas by
re-ghting teams and equipment. Studies have been
conducted to optimise the re access road density and
layout, which resulted in implementing new directives
on planning the road network in the state forests.
According to Polish law regulations, owners and
managers of forests covering over 300 ha are required
to monitor and patrol forests to detect res and raise
the alarm. Owners are obliged to maintain the water
supply for re-ghting purposes, maintain re access

275
Czerniak, A., Okoński, B., Grajewski, S. M., Kurowska, E. E., Krysztofiak-Kaniewska, A., Kasztelan, A. (2021). Technical methods of
preventing and limiting the effects of natural disasters caused by severe weather conditions in Polish forests. Acta Sci. Pol. Silv.
Colendar. Ratio Ind. Lignar., 20(4), 273–286. http://dx.doi.org/10.17306/J.AFW.2021.4.26
www.forestry.actapol.net/
roads assigned in the management plan for re-ght-
ing, adequately mark water supply locations, maintain
re-ghting equipment stations, and consult re-ght-
ing aspects of their forest management and national
park protection plans with local re-ghting authori-
ties to identify the most re-vulnerable forests.
Mass movement
Flood and heavy rainfall may activate mass move-
ment, also known as mass wasting, causing substantial
local damage to forests in Poland. Research conducted
in 27 European countries has revealed that about 6.5%
of mass movement events recorded between 1995 and
2014 might be linked to oods. It was also noted that
mass movement events immediately followed rainfall
episodes in about 90% of the cases (Haque et al., 2016).
In Poland the Carpathians (about 6% of the country’s
land area) are most susceptible to landslides, account-
ing for 90–95% of all landslides in this country. In gen-
eral, 30% of Poland’s area is mass movement prone
(Grabowski et al., 2008; Poprawa and Rączkowski,
2003) and numerous landslides occur in forests, since
the share of forest cover is high in most mass move-
ment susceptible areas in Poland, such as e.g. the Car-
pathians, share of forest area from 31% in the Beskidy
to 83% in the Bieszczady Mountains.
In Poland landslides are initiated primarily by pre-
cipitation and snowmelt, which activate ltration and
deep inltration processes coupled with saturation of
loose sediment layers on slopes (Gorczyca 2004; Gil
and Długosz, 2006; Starkel, 2006). Landslides occur
after maximum soil saturation is reached in the wake
of heavy rainfall, while a combination of the event
duration and rainfall intensity provides a sucient
amount of water. In the Carpathians the mass wast-
ing is usually initiated on slopes receiving more than
200 mm of precipitation in total, since the eect of
a rainfall event usually lasts for only several days (Gil
and Długosz, 2006).
The pattern of the reactivation of dormant landslide
locations and activation of previously stable adjacent
slopes prevails in Poland (Gil and Długosz, 2006).
Over 20 years of monitoring (starting with a very wet
year of 1997) have revealed an increasing landslide
activity, with serious events being noted every year.
Mass movements often cause signicant dam-
age to technical infrastructure such as buildings and
roads. Monitoring indicates that landslides threaten
500 sites in the central part of the Polish Carpathians
alone (Poprawa and Rączkowski, 2003). Each year the
forest sector suers from substantial damage caused
by mass land movements. The losses aect not only
forest engineering structures, e.g. roads and bridg-
es, but also individual trees and entire forest stands.
Landslides destroy trees, cause mechanical tree dam-
age, reduce tree growth, deteriorate timber quality and
reduce revenue from prospective harvests (Mozgawa
and Kwaśny, 2010).
Strong wind
In August 2017 a derecho called “the storm of the
century” passed over Poland (Pistol and Flaga, 2018).
Due to the disastrous impact of the storm in just one
night aecting over 45,000 ha, about 8 million m3 of
timber were lost in damaged or fallen trees, equiva-
lent to 20.8% of the annual harvest (Raport…, 2018).
Seidl et al. (2017) predicted that severe weather events
will become more frequent because of global warm-
ing. Hence multi-faceted response measures should
be undertaken to prevent and limit the eects of wind
damage to forests.
The main eect of strong wind events on forests is
often connected with the resulting thousands of fallen
trees, which have to be removed very quickly. E-
cient clearing of windfall-aected forest areas results
from the necessity to ensure road passability, prevent
the loss of value and technical quality of windthrows
and windsnaps, decrease re risk and provide ap-
propriate conditions for new plantings. Removing
windthrows and windsnaps in large areas is a techni-
cal challenge posing a hazard both to human operators
and to equipment.
AIM
The article aims to present our ndings and studies
concerning the eects of severe weather conditions
and weather-related natural disasters on forests in Po-
land. The review is intended to provide a background
to show implemented technical solutions and ap-
proaches dedicated to preventing or limiting damage
to forests caused by natural disasters. The methods
were developed to minimise the impact of damage on
forests in Poland thanks to the collaboration between

Czerniak, A., Okoński, B., Grajewski, S. M., Kurowska, E. E., Krysztofiak-Kaniewska, A., Kasztelan, A. (2021). Technical methods of
preventing and limiting the effects of natural disasters caused by severe weather conditions in Polish forests. Acta Sci. Pol. Silv.
Colendar. Ratio Ind. Lignar., 20(4), 273–286. http://dx.doi.org/10.17306/J.AFW.2021.4.26
276 www.forestry.actapol.net/
researchers, forest authorities and other stakeholders.
The presented solutions and approaches aiming to
counteract the impact of severe weather events on Pol-
ish forests may provide some hints or inspiration for
forest managers and decision-makers in other coun-
tries coping with similar problems.
CASE STUDIES. TECHNICAL SOLUTIONS
LIMITING THE EFFECTS OF NATURAL DISASTERS
IN POLISH FORESTS
The mitigation of scarcity of water resources
in lowlands and in a mountain forest
Based on the Karnieszewice and Stuposiany Forest
Districts
To prevent the scarcity of water resources and augment
water availability in river basins various programmes
dedicated surface runo have been introduced. The res-
ervoirs classied as small-scale water retention facilities
retain 0.83 billion m3, while the total volume is 4 billion
m3 (6.5% of the average annual runo). Such small-
scale water retention measures are often employed in
systems to augment water resources in forest areas.
Apart from reservoirs and other engineering stuc-
tures used to retain water, wetlands, being water-de-
pendent ecosystems, may also provide water for ad-
jacent areas. Natural and transformed wetlands cover
over 4 million ha in Poland (13% of the total land
area), substantially modifying water resources at the
national level (Mioduszewski and Pierzgalski, 2009).
Transformed wetlands are often subject to ecological
restoration and water resource alteration projects that
employ environmental engineering methods. Various
approaches have been applied to manage and assess
the eects of these projects on forests. Miler et al.
(2007) proposed the process to follow a specic pat-
tern: current inventory, identication of abiotic and
biotic hazards, establishing the range of passive and
active protection methods, establishing protection task
hierarchy, constant monitoring and reporting of eco-
logical eects after implementation. The State Forests
National Forest Holding, which manages over 80%
percent of forested land in Poland, is an active partici-
pant in water resource alteration programmes. More
than 75% of the State Forest districts nationwide have
participated in these water storage programmes over
the last 30 years. The most prominent programmes
completed in the last decade were implemented in
lowland and mountain forests. The hydrologic goals of
the lowland programme are to increase water resources
available to the forest by slowing down surface runo,
and to provide water to restore wetlands and water-
dependent forest habitats. Other hydrologic goals for
mountainous areas were to protect forests and other ar-
eas from erosion, oods, mass movements caused by
heavy rainfall and to support biodiversity by providing
habitats for water-dependent species.
The Karnieszewice Forest District has participated
in the hydrological restoration programme dedicated
to lowland forests, a typical example for the Polish
Lowlands as far as water resource problems are con-
cerned. The district manages over 17,000 ha of forests
dominated by Scots pine (52%), beech and oaks (20%)
growing in a mosaic of drought-vulnerable fresh habi-
tats varying in fertility. The local hydrologic system
was transformed by extensive drainage and stimula-
tion of channel runo as a result of past water manage-
ment. The project included restoration of 7 dammed
lakes and silted reservoirs, building of 17 damming
structures, such as weirs or embankments to slow wa-
ter ow in streams, rivulets and other channels and re-
store semi-natural hydrologic conditions.
The Stuposiany Forest District, located in the Car-
pathians is an example of a forest district, which has
participated in the programme assigned for mountain-
ous areas. The district area is 95 000 ha and lies on
a low mountain range (536 m to 1015 m a.s.l.). The
forest cover is 98% and the main tree species are beech
(40%), r (32%) and spruce (18%). The main hydro-
logic problems include ash oods and water erosion,
as well as scarcity of open water to support biodiver-
sity. The hydrologic alteration project for Stuposiany
involved building reservoirs to retain and manage
runo from wet meadows (7 new and one restored).
The technical solutions applied for these reservoirs
provided breeding and wintering sites for amphibian
and bird species.
Providing passability of fire access roads
through a waterlogged soil area
Inadequate quality paving of both regular and re ac-
cess roads in the forest road network is still a common
problem in Poland. Insucient load-bearing capacity of
the subgrade found in some road sections is regularly

277
Czerniak, A., Okoński, B., Grajewski, S. M., Kurowska, E. E., Krysztofiak-Kaniewska, A., Kasztelan, A. (2021). Technical methods of
preventing and limiting the effects of natural disasters caused by severe weather conditions in Polish forests. Acta Sci. Pol. Silv.
Colendar. Ratio Ind. Lignar., 20(4), 273–286. http://dx.doi.org/10.17306/J.AFW.2021.4.26
www.forestry.actapol.net/
recognised as a leading cause of poor road quality. For-
est management authorities often seek help of research-
ers and designers to nd eective technical solutions to
provide required passability of challenging road sections
and maintain coherency of the local forest road network.
We present the results of our study to work out op-
timal solutions to improve problematic sections at poor
subgrade conditions caused by high groundwater levels
and insucient bearing capacity of organic soils. We
recommend four low-cost variants of road pavement
structure: geotextile with planar underlay, geotextile
with half-mattress underlay, 0/31.5 mm aggregate and
medium sand (Grajewski et al., 2015; 2019). These
variants of road construction methods were examined
in test road sections to assess their suitability for forest
applications. Polypropylene geotextiles with track rein-
forcement were tested in cooperation with ViaCon Pol-
ska Ltd. The material innovation consists in strengthen-
ing the fabric in two 60-centimetre wide strips typically
used by vehicle wheels. The geosynthetic could pro-
vide higher strength parameters in road surface zones
where the highest pressure is applied. The application
of geotextiles in narrow forest roads appears to be
a promising solution to the problem. Furthermore, the
required strength parameters are achieved at a lower
price. The tensile strength in both directions on the
strengthened strips was 35 kN∙m–1, while outside the
strengthened lanes it was 18 kN∙m–1 with a maximum
elongation of 13% and 14%, respectively. Dynamic
puncture resistance in the strengthened strips was 10.6
mm in the strengthened lanes and 13.8 mm in the non-
strengthened lanes. Static puncture resistance in the
strengthened strips was 4.3 kN and 3.6 kN in the non-
strengthened strips. Water permeability was 9.0∙10–3
and 2.1∙10–2 m∙s–1 for both solutions. Six months after
commissioning of the road the rst assessment of sur-
face load parameters was conducted using a lightweight
deectometer (ZFG 3000 GPS with 10 kg drop weight,
Zorn Instruments) and a single-sensor static plate load
tester (HMP PDG Pro, Prüfgerätebau GmbH).
The examination of each road upgrading variant pro-
duced similar results in terms of load-bearing capacity.
Contrary to expectations, no dierences were indicated
for the geotextiles. The dierences were minor and re-
corded mainly for aggregate and sand pavements. How-
ever, according to the static plate load test results the
planar geotextile layouts were less favourable than the
half-mattress layouts. The benets of the half-mattress
layout may appear over a more extended period. The
test results for the variants of road construction tech-
nologies strongly support the recommended introduc-
tion of these solutions in forests. It should be stated that
the proposed technologies are sucient to support re
trucks and other re-ghting vehicles, although they
are not adequate to support heavy load vehicles such
as timber transport vehicles (Czerniak and Grajewski,
2014; Kamiński, 2012). Adapting these road sections to
timber haulage will require adding a suitable reinforc-
ing layer or layers to the existing subgrade.
Flooding damage of forest stands
in the Oder valley in 1997
Lessons learned to develop a flood mitigation approach
for forests
The Middle Oder river valley (located 502 km to 510
km from the river mouth) was selected to examine the
inuence of river ooding on commercial pine forest
stands and to nd solutions to limit the damaging ef-
fects of ooding on forests. The section of the river
valley was severely ooded during the 1997 ood.
The research sites were set in eight locations along the
river valley between 2.5 km to 4.0 km from the active
channel, with forest stands ranging from the sapling to
mature stand stages (20 to 90 years old). Soil and water
conditions were examined in test soil bores and pits.
For comparison, eight other sites of matching stand
and habitat features were established outside ooded
areas on neighbouring abandoned terraces. Under nor-
mal conditions, the tree stands on these research and
control sites, take up soil water from the aeration zone
as groundwater is beyond the reach of actively grow-
ing tree. Except for the 1997 ood event, the inu-
ence of the river as a stressor for trees, either through
surface ooding or through hydraulic connection with
groundwater, was never observed. Surface ooding
of the research sites in 1997 began on 13th July and
lasted for up to six weeks. The eect of oodwater on
tree stands was examined in the period of 1998–2002
(Czerniak et al., 2002).
Floodwater stagnating in forests disturbed tree
growth in pine stands led to a deterioration of stand
health and, as a consequence, caused tree dieback or
disintegration of some forest stands. Forest stands aged
between 20–40 years during the culmination of height

Czerniak, A., Okoński, B., Grajewski, S. M., Kurowska, E. E., Krysztofiak-Kaniewska, A., Kasztelan, A. (2021). Technical methods of
preventing and limiting the effects of natural disasters caused by severe weather conditions in Polish forests. Acta Sci. Pol. Silv.
Colendar. Ratio Ind. Lignar., 20(4), 273–286. http://dx.doi.org/10.17306/J.AFW.2021.4.26
278 www.forestry.actapol.net/
growth were most sensitive to ooding when the water
stagnated for over six weeks at 0.8–1.2 m height above
the ground level. These forest stands rapidly declined
during the three years following the ood; almost 75% of
the trees died, while 60% of the remaining trees were in
a very poor health condition. Mature forest stands ood-
ed for over six weeks responded by a health decrease in
about 20% of the trees, but the process of tree dieback
occurred very rarely. For maturing forest stands between
70–90 years of age ooded for 5–6 weeks a deteriora-
tion of their health status was observed in 10–15% of
the trees and it was with limited dieback. Shorter ood-
ing periods of less than ve weeks had no signicant
inuence on tree health condition. The height increment
of pine trees was reduced by about 20% after the ood-
ing for all the stand stages before maturity when surface
ooding lasted for three weeks or longer. The most sub-
stantial reduction of height growth was recorded in the
rst and second years after the ood. Growth in height
was restored relatively rapidly, within 4–5 years fol-
lowing the ood. Annual ring width was reduced in the
post-ood period compared to the pre-ood period in
both ooded stands and control forest stands. However,
typical negative pointer years did not occur directly after
the ood, as the annual ring width growth was relative-
ly regular, and the recovery period was probably pro-
longed over time. An exception was found in the stands
of decreased health that suered long-term ooding (of
at least four weeks), for which the increment reduction
after the ood was notable. The ood in 1997 occurred
after droughts of the 1980s and early 1990s. Hence, the
oodwater was both an ecological stressor for long term
ooded stands and a factor stimulating tree ring growth
of forest stands that had not been ooded for a long time
(Czerniak et al., 2002). The post-ood study revealed
that maturing forest stands were worth preserving be-
cause of their stronger resistance to ooding disturbanc-
es, greater commercial value, and shorter-term prospects
of timber harvest. However, preventive removal of the
forest stands, in which decay is substantial and regenera-
tion prognosis poor, is unavoidable.
Mass movements
Stabilising landslides
and securing roads
in the Stuposiany ForestDistrict
The Stuposiany Forest District, located in the southeast
part of Poland (the Eastern Carpathians, the Bieszcza-
dy mountain range, forest cover 98%) was selected as
an example of the application of mass movement con-
trol solutions in Polish forests.
The area of the forest district is mountainous, char-
acterised by a structural nappe with transverse tec-
tonic dislocations, which cut the layers of sandstone
and slates, where deep river valleys had developed.
The dierence of the terrain surface elevation reach-
es around 700 m. A high saturation of soil and high
groundwater levels, as well as high water stages in the
local river system are typically found in spring due to
winter thawing and snowmelt and in summer due to
heavy rainfall, which are the typical annual periods of
mass movement risk.
The main access road in the Stuposiany Forest
District (Road 19) has been under constant risk from
landslides of weathered masses. One of the most vul-
nerable sections of the road is constructed across the
landslide area, with the slope beneath the road inten-
sively eroded by the Roztoki River. The masses of
the landslide colluvium are moved when the slope is
waterlogged, blocking the road and causing extensive
damage.
The slope (the top 861 m to base 800 m a.s.l.) of
this road section has been stabilised applying a bio-
engineering method. A cribwork structure was con-
structed along the slope, and a root- and stem-division
method was applied to provide revegetation of the pro-
tected slope. To secure the landslide beneath the road,
about 4–6 rows of cribs were xed. The slope above
the road was secured by one row of cribs at various
heights. The structure employed debarked round logs
placed horizontally in the scarp; the logs were fastened
by a bracing system of sharpened poles inserted into
the slope at the right angle to the slope surface. In the
niches between the logs, shrubs were planted, while
between the cribwork structures 5.0 m-wide ledges for
passage were established. The rows of cribs beneath
the road were designed to be 6.0 m high and 5.0 m
wide.
Slope reinforcement covered the zone up to 54 m
from the valley oor. Thus, the road became secure
and passability within the forest district was main-
tained. The bioengineering method employed to se-
cure the slope, as opposed to traditional concrete and
metal technical protection, was selected for ecological
reasons. The primary function was to provide slope

279
Czerniak, A., Okoński, B., Grajewski, S. M., Kurowska, E. E., Krysztofiak-Kaniewska, A., Kasztelan, A. (2021). Technical methods of
preventing and limiting the effects of natural disasters caused by severe weather conditions in Polish forests. Acta Sci. Pol. Silv.
Colendar. Ratio Ind. Lignar., 20(4), 273–286. http://dx.doi.org/10.17306/J.AFW.2021.4.26
www.forestry.actapol.net/
strength and stability, which was achieved through the
penetration of plant roots into the soil structure. The
additional advantage was the protection of the slope
against erosion, rockfall and wind.
Plants have improved the water regime of the soil
through interception and evapotranspiration. This is
particularly important in areas prone to landslides be-
cause water is one of the main triggers for clay move-
ments on slopes. Therefore, it is advisable to extend
monitoring of the slope beyond the section of the road
already secured to cover the adjacent area. The analy-
sis of the digital elevation model reveals a texture dif-
ferentiation in the slope surface, implying deformation
of the weathered slope cover, thus indicating a poten-
tial landslide hazard.
Availability of post-hurricane forest areas
Hurricane-aected forest areas are usually inaccessi-
ble by road and transport paralysis makes it dicult to
assess the damage on the ground and thus respond ad-
equately. Such conditions occurred in Poland in 2017.
In numerous districts it was necessary to provide im-
mediate access to forests. Unfortunately, standard road
construction technologies take time and are expensive
to implement. Post-event rapid wood deterioration
lay behind the need to develop a new technology of
temporary road construction employing concrete slabs
in post-disaster areas. The reinforced concrete self-
draining slab technology was developed in coopera-
tion between the Department of Forest Engineering,
the University of Life Sciences in Poznań and the in-
dustry stakeholders (Betard Company Ltd., Poland).
The technology passed eld and laboratory tests, be-
ing currently in the patent pending process.
Compared with standard technology, the advantag-
es of the developed slabs include shorter construction
cycle, increased structural stability, improved traction
control, the ability to facilitate drainage of the road
surface and driving uphill, as well as exposed aggre-
gate surface for improved slab aesthetics.
DISCUSSION
We present various technical approaches applied to
limit the damaging eects of severe weather condi-
tions on forests in Poland. The presented concepts and
technical solutions can raise objections by scientists
who claim that engineering interference with the en-
vironment is not benecial as a rule. We think that an
appropriate design and execution of engineering struc-
tures can mitigate potential negative environmental
impact. In Poland forests cover is 30%, of which more
than 40% is under area-oriented forms of nature con-
servation, 38% of the State Forests (over 2.8 million
ha) are covered by the Natura 2000 network of nature
protection areas. As a principle, the approaches de-
scribed in this paper have been developed to be com-
pliant or support the Natura 2000 protection objectives
to preserve habitats and species.
Water resource management
Two national-scale water management programmes
have already been completed in the State Forests in
Poland, while a new programme is currently under-
way. The main aims of these programmes are to miti-
gate drought eects, protect water-related ecosystems,
adapt forests to climate change, and limit the eects
of water erosion and oods. The hydrologic eect of
the nished programmes is 2.5 million cubic metres
of stored water in thousands of sites in lowland and
mountain forests.
Forest management approaches employed for river
alluvia should recognise the risk of damage caused
by severe oods, since management practices do not
have sucient potential to limit ood losses adequate-
ly. Modifying the species and age structure of forest
stands cannot usually produce a satisfactory eect in
limiting damage in the case of long-term oods. Some-
times redening the aims of forest management is the
only solution left. Supporting forest renaturalisation
while recognising oods as a natural ecological pro-
cess seems to be a reasonable choice (Czerniak et al.,
2008, EEA, 2019; Göthe et al., 2016; Hornung et al.,
2019; Kamiński et al., 2011; Koprowski et al., 2018).
The heaviest oods are dicult to control even by the
most advanced river and valley water engineering sys-
tems. The priority of ood protection is to secure peo-
ple, settlements and industrial areas (Dumieński and
Tiukało, 2016; EEA, 2019; Głosińska, 2014). During
the heaviest oods in Poland, the levees were occa-
sionally breached intentionally to create improvised
polders in areas of lower protection priority, such
as forests and agricultural land (Maciejewski et al.,
2011a; 2011b; NIK, 2013). Under these circumstances

Czerniak, A., Okoński, B., Grajewski, S. M., Kurowska, E. E., Krysztofiak-Kaniewska, A., Kasztelan, A. (2021). Technical methods of
preventing and limiting the effects of natural disasters caused by severe weather conditions in Polish forests. Acta Sci. Pol. Silv.
Colendar. Ratio Ind. Lignar., 20(4), 273–286. http://dx.doi.org/10.17306/J.AFW.2021.4.26
280 www.forestry.actapol.net/
management of river valleys needed to be revised con-
sidering the needs and expectations of the stakehold-
ers. Nowadays, within the integrated management of
rivers developed and implemented after the 1997 and
2010 oods the water management in the river val-
leys has been altered. This systemic approach supports
the creation of polders mainly on sites that will benet
ecologically from ooding. The adopted solutions aim
at limiting the negative impact of ooding on settle-
ments and critical industrial sites, while planning of
polders in the ecological spatial system of river valleys
also includes needs of forest management to protect
these forests that should not be ooded. The ood pro-
tection system focuses on controlling the ood wave
by water reservoirs, dry reservoirs, polders and lev-
ees. Local drainage systems are prepared to eciently
drain oodwater from the bottom of the river valley
for strict oodwater protected sites (Głosińska, 2014;
Matczak et al., 2017; NIK, 2011; 2013; Pawlaczyk,
2020).
The systemic ood control approach has been in-
troduced, for instance, in the Domaszków-Tarchalice
polder system in the Middle Oder valley. The im-
plementation is a multi-partner cooperation between
WWF Poland, the State Forests, the local govern-
ment, valley and river management institutions and
the German Federal Environmental Foundation. The
polder was established in an alluvial valley (about 600
ha) that was opened for ooding by removing some
sections of levees and constructing a system of em-
bankment overows to enable oodwater to enter the
oodplain forest, oxbow lakes and meadows managed
by the State Forests (Królikowska et al., 2015). The
system reduced ooding exposure of the commercial
forest covering about 2000 ha downstream in the Oder
valley. These are pine monocultures located in the val-
ley section that was ooded in 1997 and the conducted
investigations led to the formulation of ood protec-
tion recommendations (Czerniak et al., 2002).
Landslides
In order to prevent the consequences of landslides in
Poland the Landslide Counteracting System (SOPO)
has been implemented. The project is nanced by the
government (the Ministry of the Environment) and
was coordinated and implemented by the Polish Geo-
logical Institute – the National Research Institute. The
main aims of the programme include a detailed survey
of the landslide areas and the areas where the landslide
hazard is the highest, creating documentation, and
monitoring selected locations. The programme was
initiated in 2006 after numerous landslide incidents,
which led to infrastructure damage and signicant
material losses, especially in 1997, and in the period
of 2000–2002. Before implementing the programme
estimated number of landslides was about 20,000. The
inventory conducted by SOPO has indicated about
60,000 landslides so far, but it has been assessed that
approx. 100,000 landslides may be inventoried (Po-
prawa and Rączkowski, 2003; Wójcik and Wojcie-
chowski, 2016).
The results of the SOPO survey are stored in a da-
tabase and mapped to present the location, range, and
activity level of the landslides, together with the docu-
mentation in the form of information cards created for
each landslide following the respective recommen-
dations (Grabowski et al., 2008; http://geoportal.pgi.
gov.pl/portal/page/portal/SOPO). The data indicating
these geological hazards are being used for land man-
agement and planning.
About 60 landslides are currently being monitored
within the state geological survey programme, where
the movements are registered using the depth meas-
urement method (inclinometer measurements) and
the surface measurement method (measurement with
the GNSS satellite navigation system and laser scan-
ning). Hydrogeological observations of groundwater
tables and precipitation are also recorded. The surveil-
lance and monitoring systems are often set up by the
road administration and local government bodies dur-
ing construction works to secure and protect the area
against landslides (Wójcik and Wojciechowski, 2016).
Fire protection
The re protection infrastructure, such as road net-
works providing re access, is a crucial forest man-
agement element. Forest roads can also alter spatial
patterns of ignitions, as well as modify and limit re
boundaries. Roads can function as supplementary
rebreaks supporting safer and more eective wild-
re management (Katuwal et al., 2016; Narayanaraj
and Wimberly, 2012; Simpson et al., 2019; Yocom et
al., 2019). Therefore the distance between any point
in the forest and the nearest public road (excluding

281
Czerniak, A., Okoński, B., Grajewski, S. M., Kurowska, E. E., Krysztofiak-Kaniewska, A., Kasztelan, A. (2021). Technical methods of
preventing and limiting the effects of natural disasters caused by severe weather conditions in Polish forests. Acta Sci. Pol. Silv.
Colendar. Ratio Ind. Lignar., 20(4), 273–286. http://dx.doi.org/10.17306/J.AFW.2021.4.26
www.forestry.actapol.net/
motorways and expressways) or a forest road function-
ing as re access should not exceed 0.75 km or 1.50
km, depending on the assumed re hazard category of
the forest (the National Law and internal regulations
of the State Forests). Fire access roads in forests serve
the same function as re roads in urban areas and pro-
vide the basic transport network to execute all tasks,
including planning and organising rescue and re-
ghting missions (internal regulations). There is about
107,000 km of forest roads within the State Forests,
of which almost 47% can serve as re access roads
(Czerniak et al., 2016; Trzciński and Czerniak, 2017).
Contemporary research on re protection infra-
structure is focused on optimising the utilisation pro-
cedures of re access roads for rescue, operation of re
vehicles, tactics and re-ghting methods (Grajewski,
2019; Grajewski et al., 2019). The research concerns
optimising the network density and geometric param-
eters of re access roads, developing new technolo-
gies to increase load-bearing capacity (Czerniak and
Kamiński, 2003; Kamiński, 2007) and optimising the
eciency of supervision and the commissioning pro-
cess for constructed re access roads. Despite the high
annual costs of modernising road networks in the State
Forests the needs continue to be extensive. Fire access
road systems still require improvement, especially in
terms of the load-bearing capacity of these roads (Gra-
jewski, 2019).
A fundamental problem of re protection in for-
ests is to provide an appropriate amount of water for
reghting. The water supply system includes natural
lakes and ponds, reservoirs, rivers, other water bod-
ies and underground water. The basin permeability is
a common problem in the case of availability of water
resources. Therefore, water bodies and water retention
structures constructed within water management pro-
grammes in the State Forests are adapted to provide
water for reghting. Forest areas of the highest re
risk require establishment of strategic water supply
points. The dierence from the basic water supply
points results from their greater water storage capacity
and the potential of servicing at least three reghting
vehicles and fuelling them simultaneously (Przysiecki
and Fijałkowski, 2015).
The approaches presented in the article show that
it is feasible to limit the damaging eects of drought,
ood, re and landslides on forests by applying
engineering methods. However, it is not possible to
eciently secure tree stands against strong winds.
Modifying the forest stand structure and stand man-
agement methods can decrease susceptibility of trees
to wind damage; however, as practice shows, a major-
ity of forest stands cannot resist the negative impact
of strong winds. Therefore, assuming that storms will
continue to damage forest stands, it is necessary to
focus on developing procedures that more accurately
predict storms, estimate the damage and immediately
provide technical solutions to limit losses.
CONCLUSIONS
We have shown that forests may be protected to some
extent against the eects of severe weather conditions
by the application of engineering solutions. Such solu-
tions contribute to protecting both commercial forests
and habitats, valuable plant and animal species, in-
cluding large mammals (the European bison, bear and
wolf), which are considered important components of
the biosphere in Europe. The selection of any particu-
lar approach has to be adequate, not only to meet spe-
cic needs, but each implementation of engineering
structures and methods requires potential side eects
to be addressed and reduced during the planning and
designing stage.
Extreme weather, droughts and torrential rain
events are becoming increasingly frequent. Dry pe-
riods are often intertwined with wet spells forcing
modication of water management methods applied
in forests. Today, eorts are focused on securing wa-
ter availability to sustain forest habitats and support
the growth and development of forest stands. Water
storage alteration at various spatial scales through
the implementation of water engineering solutions is
the leading water management practice to pursue this
goal. The assessment of completed water storage pro-
jects and implemented engineering solutions usually
reveals various hydrological, ecological and positive
functional eects on the forest environment within
a short period, such as e.g. increased soil moisture
content, improved tree health and growth conditions,
greater biodiversity, and even a rise in forest value for
tourism and recreation.
Damage caused by extreme ooding, especial-
ly during the 1997 and 2010 events, forced forest

Czerniak, A., Okoński, B., Grajewski, S. M., Kurowska, E. E., Krysztofiak-Kaniewska, A., Kasztelan, A. (2021). Technical methods of
preventing and limiting the effects of natural disasters caused by severe weather conditions in Polish forests. Acta Sci. Pol. Silv.
Colendar. Ratio Ind. Lignar., 20(4), 273–286. http://dx.doi.org/10.17306/J.AFW.2021.4.26
282 www.forestry.actapol.net/
authorities to redene approaches and priorities of
management in alluvial forests. Systemic methods
have been developed through the cooperation of all
stakeholders in integrating better protection against
ooding within management practices of rivers and
river valleys. The strategy of mixing strict protection
for some parts of the river valley with reduced protec-
tion and measures enabling ooding in other sites is
central to this approach. Some parts of river valleys
were opened for oodwater to create polders and con-
trol ood waves, thus allowing other valley parts to
be protected from ooding. The State Forests National
Forest Holding benets from these systems, since val-
uable commercial forests, vulnerable to ooding, gain
protection, while forests beneting from ooding are
usually included in the polder system. The water engi-
neering systems have been introduced to support this
strategy. The State Forests participated in introducing
these systems and integrated them into the water man-
agement practice in forests. The eectiveness of this
approach was conrmed during the ood on the Oder
in 2020.
Engineering methods and solutions provided
passability of re access roads in poorly perform-
ing sections by altering the load-bearing capacity of
road pavements. The engineering upgrading of road
networks facilitated strengthening of re protection
systems in forests. The use of geotextiles has been
proven a particularly eective, low-cost solution help-
ing to signicantly reinforce narrow forest roads. The
performance of geosynthetics as an environmentally
neutral, low-cost material has potential for broader
application in the construction of road pavements of
unbound aggregates. Thanks to the use of geosynthet-
ics the thickness of expensive aggregate layers may
be reduced without loss of their load bearing capacity.
The application of a geosynthetic mattress allows to
raise the road surface without extending the width of
the right of way.
Mass movements, especially over the last two dec-
ades, caused increased material losses. Removing or
reducing landslide damage often exceeds the nancial
capacities of the local authorities and land managing
parties. The most widely applied methods to secure
landslides include concrete retaining structures, e.g.
systems of poles, retaining walls, buttresses, grillage,
etc. reinforced by steel anchors. Geosynthetics can also
be used in the protection of shallow landslides. These
methods are widely discussed in geoengineering lit-
erature. Less popular approaches of slope stabilisation
need to be focused on by forest authorities. Environ-
mentally friendly and ecologically neutral solutions to
be promoted, employ natural materials (stone, wood,
reed, fascine). Bioengineering structures provide an
optimal solution in protecting slopes against erosion
by altering soil moisture, controlling surface drying,
forming crevices, and reinforcing soil surfaces. These
natural solutions are gaining in popularity. The land-
slide control project in the Stuposiany Forest District
is a good example of this trend, although steel, con-
crete and geosynthetics still dominate. These methods
are dedicated to forests and areas of high natural value,
which require protection against landslides.
Forest damage caused by severe weather may not
be eectively limited without an ecient road net-
work. Therefore, the re access road network is an
essential component of the forest re protection sys-
tem, which has to be maintained and modernised to
sustain operational capability. The technical solutions
developed for the State Forests have facilitated estab-
lishment of road sections of inadequate load bearing
capacity on waterlogged soils under all weather con-
ditions. The experience gained during the clearing of
windthrows and windsnaps over thousands of hectares
after the 2017 storms in Poland indicates that immedi-
ate actions are crucial. An ecient network of tempo-
rary and logging roads is a necessary asset to accom-
plish this task. Module slabs made of various materials
have been proven to be the most benecial solution.
The most eective solutions in Poland involve rein-
forced concrete slabs placed along the tyre track line.
These slabs can be stored and re-used if another occa-
sion for their need arises.
ACKNOWLEDGMENTS
The authors would like to express their thanks and
appreciation to Rafał Borkowski for his help in the
preparation of this manuscript.
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286 www.forestry.actapol.net/
TECHNICZNE METODY ZAPOBIEGANIA I OGRANICZANIA W LASACH POLSKICH SKUTKÓW KLĘSK
POWSTAŁYCH W WYNIKU EKSTREMALNYCH ZJAWISK POGODOWYCH
ABSTRAKT
Zmiany klimatu, obserwowane w ostatnich latach, manifestują się wzrostem częstości i intensywności zja-
wisk pogodowych takich, jak silne burze, wiatry, opady deszczu, fale upałów, susze. Ich konsekwencją jest
wzrost w lasach szkód powstałych w wyniku powodzi, ruchów masowych, niedoborów wody, pożarów,
wiatrów oraz pogorszenia stanu zdrowotnego drzewostanów w Europie. Czynniki stresu ekologicznego po-
wiązane z klimatem zwiększają podatność drzewostanów na wiele wtórnych zagrożeń chorobowych i szkód.
Ta nowa, bardzo dynamiczna sytuacja zmieniła znacząco warunki prowadzenia gospodarki leśnej w Pol-
sce. Ustalone dotychczas podejścia i sposoby wymagają werykacji oraz wypracowania rozwiązań nowych
w celu sprostania pojawiającym się wyzwaniom i zagrożeniom. Stało się oczywiste, że działania z zakresu
hodowli lasu w tych warunkach powinny być wspierane aktywnie różnymi rozwiązaniami z inżynierii eko-
logicznej i budowlanej, aby zapewnić ich lepszą efektywność. Praca jest próbą przedstawienia aktualnej pro-
blematyki dotyczącej rozwiązań inżynieryjnych stosowanych na potrzeby ochrony, przeciwdziałania i ogra-
niczania skutków ekstremalnych zjawisk pogodowych w polskich lasach. Wykorzystano badania własne oraz
odniesiono się do innych rozwiązań stosowanych w lasach w zakresie optymalizacji sieci dróg leśnych, ogra-
niczania skutków pożarów, powodzi, ruchów masowych i szkód od wiatru, kształtowania warunków wod-
nych i zapobiegania suszy. Przedstawiono też przykładowe rozwiązania inżynieryjne stosowane w Polsce.
Słowa kluczowe: infrastruktura inżynieryjna, ekstremalne zjawiska pogodowe, ochrona lasu, ograniczanie
szkód