GB No. 1(24)/97
FLOOD IN POLAND
SHORT ANALYSIS OF THE CAUSES OF THE FLOODS IN POLAND
The floods in Poland over the last
two weeks had large human and material impacts. Following
intensive rain in the south of Poland and in the Czech Republic,
both the Wisla and Oder river systems were not able to deal with
so much water. In all areas the rivers started to flood the
surrounding land and induced land slides in the mountains. The
floods left behind an area dirty and destroyed. Many people lost
their houses, farmers lost their crops and animals and some even
lost their lives. The victims of the flood needed to be helped
urgently and a large national and international solidarity action
has already partly met their needs. Now that the flood waves have
left Poland it is time to evaluate the causes of the flood. We
have been able to see that the flood waves that took their
destructive path through Poland were very high but rather short:
this indicates that there are serious problems with the way in
which water in the riverbed is absorbed - ie the water
retention capacity of the riverbed. High, short flood wave as
were observed, are caused by a rapid discharge of water in the
upper parts of rivers, and the wave is maintained by a quick flow
through in the lower parts of the river. The following three
elements influence the water retention capacity of the riverbed
and have either a negative or positive impact on it.
- Vegetation types in the riverbed: forests having a high water retention
capacity, while built areas have no water retention capacity.
- Regulation of streams in the riverbed: the better regulated, the
quicker the discharge of water and the higher the flood wave.
The capacity of artificial water retention objects such as reservoirs
and polders that are meant to temporarily stop at least a part of
the water running through the riverbed. All of these elements and
the way they participated in the floods will be discussed.
VEGETATION TYPES IN THE RIVERBED
General data on this
issue is available for all of Poland over a long period of time.
As most of Poland consists of the Wisła riverbed and a
significant other part consists of the river Oder, one may say
that this data can be indicative for the development of
vegetation over the last years. In figure 1 we can see how land
use has changed in Poland from 1946 to 1995. A slow decrease of
fields and a slow rise of forest and woodlands is evident.
Pastures, orchards and other uses remained on the same level.
This suggests that the water retention capacity has been rising
as forests are 17 times better in absorbing water then fields.
Nothing is less true as one considers the enormous impact of
acid-rain. Presumably since 1960 forests have been under severe
pressure. This pressure is not only expressed in the traditional
acid-rain effects, like decrease of needles and leaves, but also
as a general decreased resistance of forests for plague insects,
fungi and illnesses. Acid-rain enhances the growth of grasses in
forests which causes them to function more like orchards than
forests. If one corrects the data and suggests that all forests
which are damaged by more then 25% can be only half as effective
in water retention, than one comes to the conclusion that instead
of a rising water retention capacity in Poland it is decreasing. This is
shown in figure 1.
FIGURE 1
FIGURE 2
Another illustration of this is figure 2 where it is clearly shown that,
while official data suggests that there is
significantly more forest in Poland in 1995 then in 1945 the same
official data suggests that this forest is approximately half as
healthy as in 1945. This prediction is not good when it comes to
water retention capacity of river beds. The fact that the floods
occurred in their most extreme manner along the Oder indicates a
strong connection with the devastation caused by acid-rain and
failing protection of forests - as the upper part of the
riverbed of the Oder consists mostly of the area called the
"black-triangle" (were devastation due to acid-rain is
the highest).
FIGURE 3
REGULATION OF RIVERS AND STREAMS
So-called regulation of
rivers and streams was probably most popular in the beginning of
the 1960's. From that moment, a steep rise in regulation may be
seen. Currently more then 50% of rivers in Poland have been
regulated (as seen in figure 3). Although
many hydrologists suggest that regulation is a way to prevent
flood damage, one may doubt that. The level of regulation of
rivers is rather high, and as we have seen with our own eyes, its
effectiveness in the prevention of floods was rather poor.
Regulation consists of making rivers shorter, straighter and
making their banks and bed out of concrete; for this reason water
discharges much faster. Data gathered in the Netherlands
indicates that often regulation in the upper section of streams
is responsible for floods in areas where, historically, floods
never occurred. Regulation of rivers makes flood waves higher and
stronger and therefore more destructive. If one reviews figure 3
one may conclude that Poland has a high and increasing level of
river regulation. This regulation is one of the causes that
contributes to high and relatively short flood waves. In Poland
there is still a strong tendency to regulate rivers and streams.
Although the Germans, for instance, have already concluded that
this is a dead track. Instead of regulation, re-naturalisation is
implemented as a way to prevent floods. The re-naturalisation of
the Ems river, for example, will take 30 years and an investment
of 4 milliion German marks. In the process, the regulations
established before will be destroyed.
THE CAPACITY OF WATER RETENTION OBJECTS
One of the immediate
suggestions after the floods was that there should be at least 20
more water-reservoirs like Czorsztyn (in the upper-partitions of
the Oder and Wisła). Figure 4 proves just the
opposite.The riverbed of the Oder has, although there is data lacking from the
Czech Republic, a much larger artificial water retention capacity
than the Wisła when compared to its outflow. Nonetheless, damage
along the Oder river was
significantly larger. Instead of preventing flooding, as
suggested in the case of Czorsztyn, the large water retention
reservoirs did not prevent floods. In many cases, one may even
say that they provoked flooding by giving the people living
down-stream the idea that living "in" the riverbed is
safe. This is especially true for the Oder were most of the dams
are much older then in the Wisła riverbed. Also, large water
retention reservoirs are like gas-tanks without a safety outlet
- if things go wrong they really go wrong. The case of the city
Nysa illustrates that, at a certain moment a water-reservoir is
just simply full. Building objects that slow-down the flood
waves, like polders, would be more appropriate than building
large water retention reservoirs. One of the more relevant
arguments for a country like Poland is that they are only used in
periods of flood emergency, and during normal times the areas can
be used for agricultural purposes. Another method,
environmentally friendly, can be to improve small water retention
in forested areas. By these means, often the same water retention
capacity can be established without destroying agricultural land
and creating enormous sewage reservoirs. Building large
water-reservoirs is, indeed, a way to make enormous investments
and allows many people to make money in the short term. However,
it does not guarantee much work in the maintenance phase, and is
therefore an un-sustainable method.
FIGURE 4
DEVELOPMENT OF A CATASTROPHE
It seems obvious that
the main reason of the catastrophic floods in Poland in the last
three weeks is the deterioration of water retention capacity in
both the Wisła and Oder riverbeds. It might be clear that the
situation in the case of the Oder is significantly worse than in
the Wisła. The terrible state of the forests is due to acid-rain
and also ineffective forest management. Although the area of land
given the name forest has increased, their quality has been
decreasing. This has decreased the water retention capacity of
the riverbed as a whole, and rain water quickly found its way
down with the destructive effects we have seen. The rain water
coming down from the mountains out of the forests did not find
many barriers in it's path - as most small streams are
regulated and do not irrigate the land around the river or
stream. The only barrier some rivers found were water retention
lakes, although they were only able to stop the water for a very
short time. The large investments done in water retention and
regulation of rivers in Poland did not bring the tax-payer any
practical benefit. After overcoming the barriers, the huge and
steep flood waves raged down streams not prepared for such waves
without polders, good dikes or anything else that could slow down
so much water
SOLUTIONS
One of the first things
that should be done is to improve the quality of forests and
reduce the emissions responsible for acid-rain. Although it looks
like the quality of forests is improving, the general water
retention capacity in the riverbed can be increased by seeding
new forests. One may also think of increasing the water retention
capacity of forests by means of developing small water retention
objects like small dams and areas were streams are enhanced to
flood the forests. Small rivers in the upper partitions of the
riverbed should be re-naturalized such that they are maximally
allowed to flood areas were they do no harm and their destructive
powers are decreased. Flood forests and polders should be
developed in order to decrease the destructive powers in the
lower parts of the riverbed. As measures in the upper-streams
always have impact on the lower laying partitions of the
riverbed, an integrated management should be created that
monitors the rivers as a whole and is able to prevent
decision-making of local or Voivodship authorities that will have
negative consequences for the lower laying areas.
Spatial-planning should take into account the specifics of the
riverbed and should prevent buildings from being established in
areas with high flood risks. In the process of coming to good and
sustainable flood prevention management in Poland, local,
regional and national authorities should co-operate with the
community and especially those groups interested in participating
practically in undertaking these tasks.
ing. Ernst Jan Stroes
Foundation for the Support of Ecological Initiatives
Ecological Flood Prevention Fund
SOURCES
- Statistical Annual Reports on Environmental
Protection for 1996 and 1994, Central Statistical Service,
Warsaw Poland.
- The channels spill out!, Association for
the Earth - Green Federation Oświęcim Group, 14 July 1997,
Oświęcim, Poland.
Appearing in Polish mass media the past few months were many opinions from
the hydrotechnical lobby about the reasons for the flooding and
methods of flood prevention. Unfortunately these were only
one-sided views. The reason for publishing these ideas was to
gain acceptance of polish society for a technocratical vision of
river channelization through regulation. If this happens, not
only would the most beautiful parts of Polish river valleys be
completely destroyed, we would also witness more flooding in the
future.
Because of these views we would like to present some
facts which will allow you to make objective opinions about the
reasons behind the flooding and make some educated conclusion for
the future.
- The reasons for
the latest floods in Poland are poor forest management
(especially after the Forest Law in 1992), the greenhouse effect,
the regulation of so many rivers and mountain streams, poor
condition of existing hydrotechnical structures, and bad
management of spatial planning and flood prevention.
- The flora that
existed in the past restrained surface water flow and made
conditions better for water infiltration into the soil. It is
well known that large amounts of humus and deeply-rooted trees
improve the capacity of the soil to hold and regulate water flow
much more than arable land or meadows.1 One square
meter of forest soil can hold as much water from rain or snow
melt as seventeen square meters of grazing land.2
The effect of cutting large amounts of trees leads to a decrease
of natural water retention. Instead of water being infiltrated
into the soil, it flows down the watersheds into the rivers much
faster than normal. Besides cutting the trees, there is also the
problem of forest health. Overall, the percent of healthy trees
is decreasing; and is now less than 10% of the entire tree
population. Trees with diseases are currently over 50% of the
total tree population. For example, in the spruce tree population
the disease rate is 70%, and fir tree populations have a disease
rate of 80%. The restructuring of forests in the 19th century for
increased wood production, from broadleaf trees to conifer trees,
completely destroyed the natural water balance.
- In the last few years, because of
irrigation for farming, over 24, 500 km of rivers and streams
were regulated. Rivers and their banks were transformed into
concrete canals (the best examples can be seen in the Zakopane or
Podbeskidzie region), and/or a 'netting' was constructed using
rocks and iron and placed on the river bottoms and banks. There
were also cases of natural river ways being straightened out and
dredged. It is known that when you straighten the natural path of
a river by 20% the speed of the water increases and culminates in
an increased flow of 50%.3 You can see
the effects of this problem by looking at the Odra River;
regulation of this river in the 19th century straightened the
river path by 20% (Zbigniew Jakubiec claims it is more like 30%).
For example, the outlet from Krapkowice to Nysa Kłodzka was
straightened by 14%, below the outlet of Warta it was 24%. On the
last part of the cross-cut there was an increase in the Odra's
median water level about 4 meters above the bottom of the valley.4
You must realize that every method of regulation, excluding
ecologically sensitive ones, more or less caused the shortening
of the rivers length.
- Shortening the natural water path and
time of water flow, because of regulation work, can cause
imposition of water coming from the tributaries. This happened in
1995 on the Ren River from Bazilea to Karslruhe. Because of the
hydrotechnical structures on this river, the flood wave was
intensified from what would have been 64 hours to only 23 hours.
At the same time, the hydrotechincal structure of the upper Ren
caused an increase of flow in the Cologne River by 700-800
m3/sec, raising the water level by about 40 cm.5
It should be noted that the Ren is an example of one of the most
regulated and manipulated rivers. Because of this manipulation,
floods have occurred twice in the recent past, in December 1993
and January 1995. In Poland during the 11th and 12th of July, the
area from Opole to Wroclaw was imposed by the Nysa Kłodzka wave
and the Odra wave.6 Because of this, Wrocław was completely
inundated by the flood waters and runoff from Opole was delayed.
- The regulation work of cutting trees
and flora near the rivers and streams (main ingredients needed
for increasing the water retention capacity of the river's
corridor) caused natural water retention to decline drastically.
It is difficult to say how many forests have been cut up to now
because of regulations. This tragedy can be seen by the
relatively small amount of rivers in forested areas which exist
in the territory of Poland today; only about 5% of the previous
area.7 The rest has been destroyed by river regulators.
A good example of the efficiency of natural water retention and
flood prevention can be seen by the results of scientific
research made in the hydrologic year of 1996-1997. This research
was conducted on the drainage basin of the Czarna Woda; an area
which is covered by 63% forest and 34% grassland. The drainage
basin of the Biala Woda, on the other hand, is only 21% forest
and about 76% grassland. The research showed that from August
until September of 1996 water runoff from the Biała Woda was
higher. The runoff reached a culmination of about 387 dm3/s/km2,
and at the same time the Czarna Woda was about 270 dm3/s/km2. The
hydrotechnical viewpoint of retention and the need for cutting
forests and grasses in the valleys is absurd. This kind of
thinking can only lead to more situations of catastrophic
flooding that we previously experienced.
- Regulation of the rivers, and the
associated cutting of trees close to the rivers, caused the
increased risk of floods-especially on the lower parts of the
rivers.
- The information which is being spread
by the hydrotechnocrats concerning regulation work for making a
shorter path from the rivers to the sea concerns us ecologists.
Revolutionary changes are being made right now in high-tech
countries concerning the prevention of floods; but in Poland the
idea of regulation as a golden rule for flood prevention is still
alive. It is forgotten that the flood wave speed is greater and
much more abrupt than the wave with a slow speed; an abrupt wave
with an identical volume has a higher cumulative flow.8
Channelizing the rivers doubles the speed of the water and
intensifies the power of the water; the same water which
destroyed bridges and houses in the surroundings.9
- The flooding which occurred in 1993
on the Mississippi, Missouri, Ren, Pad, and Mozella Rivers (all
of which are regulated and have many retention reservoirs on
their tributaries) show that it is necessary to change the
attitudes about flood prevention by our government. For example,
on the Mississippi 29 steps were made above the connection with
the Missouri and 36 reservoirs on the tributaries of the
Mississippi along with 1000 km of embankments. Because of this,
the floods overflowed into 12 states causing the evacuation of
37,000 people, the destruction and damaging of 40,000 buildings,
and the death of 47 people.10
- Today, in high-tech countries, large
amounts of money are being spent on the re-naturalization of
rivers. But in Poland, the hydrotechnocrats are playing the
regulation game and are trying to exploit the latest floods as an
opportunity for using our tax zlotys. In Germany's Ruhry basin a
program is underway trying to recover the natural corridors of
fragmented rivers and streams. In Oberhausen they recovered some
hundred meters of natural corridors and water flora, the flora
which is near the water and in the streams of Lapkes Muhleband
has shown the foreigners to be a big success. They have also
worked to recover the corridor of the Emscher River with the
biological surroundings, the farming and the factories in the
area of the Ladschaftparks u Dusibug - Nord.11
This work is very slow in the short-term because
revitalization is really expensive even for rich countries like
Germany. For example, re-naturalization of the Ems River and its
tributaries will take about 30 years and will cost 3 billion DM.
Over half of this money must be paid by 2.4 million citizens who
live in the area surrounding the river; this amounts to 1,000 DM
per person.12 The old path of the Ren can be re-constructed
with the natural corridor as well as the flood plains and will
cost 500, 000 DM/km. Maybe our hydrotechnocrats want to regulate
the river because the future technocrats will find work for
re-naturalization of the corridors that they destroyed. Something
to think about.
- Another reason for the flooding in
Poland is because of the small distance between the embankments
and the corridors, also the embankments are in bad condition. The
embankments close to the corridors radically decreased the flood
plain and increased the speed and the height of the water. The
bad condition of the embankments caused their destruction and
infiltration through the embankments. About 2,000 km of the
embankment need to be modernized. In 1991, according to the main
statistical evidence, Poland regulated 700 km of river and made
64 km of embankments; the primary flood prevention measure. In
the next few years the situation was similar, Poland regulated
more km of the river and built fewer embankments. Also in Poland
were some voivodships which didn't build one meter of embankments
and regulated the rivers and the mountain streams (e.g.
bielskie). There are good reasons for moving the embankments out
from the river corridors. The embankments could be lowered,
increasing the capacity of the flood plain, decreasing the level
of overflow, decreasing the speed of the flow, and helping
prevent destruction (losses on the banks and the flora). The
bigger capacity of the valley flood plain will make better
conditions for the infiltration of the flood water, increasing
the retention and decreasing the risk of catastrophic floods of
the lower parts of the river. If the elimination or moving of the
embankments is impossible, this can be done by making culverts or
partly curving the embankments for controlling flows.13
- In the tributaries of the Odra 16
polders were built with a holding capacity of 167 mln m3 (10
polders above Wrocław and 6 below the outlet of Warta).14
- Right now in Poland the flood
prevention strategy depends on "man moving water out".
Right now there are some leading investments that depend on
building retention reservoirs and regulating the rivers and
encouraging people to invest in the "protected" valley.
Man's pressure on the environment, collectively with the river
valley management, intensified industry and farming production
has destroyed the places for the natural retention. Today there
is no place for flood water to flow freely, but instead it must
flow into the cities. The risk of flooding should be included at
the beginning of the management study. This only makes sense
because the management study in the one municipality can
influence flooding in the streams which are downstream; and right
now there is no communication between municipalities.
- The hydrocrats have destroyed most
of the riparian forest areas, areas which are compared to
tropical rain forests by scientists as they exist in only a few
places in our country, e. g. in Oświęcim they play a special
role in the flood prevention system. It is because of the
riparian areas, because the embankments in the center of the city
are in bad condition, that there wasn't any destruction of the
embankments. During the few floody days they functioned as
buffers and took the whole power of the water on themselves.
- In the last few years in Poland the
network of observation points of the institute of meterology and
water management was eliminated which lead to decreased
information about hydro-meterology thus increasing the chances
for false decision-making forecasts in the future.
- Because of the above fact we propose
some ideas of work which should be done.
15.1 Technical method:
- Re-naturalization of the majority of channelized rivers in Poland
- Modernization of existing protection structures
- Building floods embankments, bypass channels (floodgates), natural polders, and networks of
small retention reservoirs (unregulated) only in special
situations (e. g. in places where the river intensity erodes the
banks of the river......but every case should be treated
individually)
- Re-introduction of beavers
- Expansion of the natural flood plains
- Planting trees in the mountains
- Stop cutting riparian forests in the valleys and re-planting what was cut
- Searching for the reasons of floods, not only in the cities but
in the whole river basin, especially in the upper parts of the
rivers
- Development of warning systems
15.2 Non-technical methods.15
A. Administrative and legislative procedures
- Prepare and make water laws and other laws
connected with spatial planning, where the main purpose is to
stop building or investing on treated places which lead to
decreases and eventual losses
- Regulate spatial management on the
risk areas just like systems of prohibition, expropriation,
economical and fiscal tools, and new ideas on insurance policy
- Exchange the law from 29 August 1997 about protection and
management of environmental protection; especially the paragraphs
which allow cutting trees between the embankments.
- Give the right to the upper committee to make a decision in situations that
contradict with a lower committee and share the competency and
methods of financing between them
- Prepare new mechanisms for making decisions and supporting the decision process in the
matter of flood prevention in accordance with sustainable
development
- Offering alternatives to investors who intend to
build something in the risk area
- Preparing ideas for spatial management of risk areas
B. Operational work
- Preparation and actualization of the operational plants for direct flood
prevention including the possible damage situations
- Coordination of the operation plan
- Organize exercises for decision making
games of improving coordination for every committee of flood
prevention
- Conduct workshops for the services, citizens, owners
of the building in the risk areas, and for preparing the direct
prevention
- Modernization of hydrometerological services which
increase the certainty of a forecast
- Implement modern systems for
collecting, transforming, and distributing information for all
work which is done at every level of a flood prevention committee
Association for the Earth - Green Federation Oswiecim Group
Translation: Tomek Walkowicz and Aaron Rice
1. K. Pazdro, Hydrogeologia ogólna, Warszawa 1997
2. K. Forowicz, Europa traci drzewa; "Rzeczpospolita" 12-13 lipca 1997
3. E. Bobiński, J. Żelaziński; Instytut Meteorologii i Gospodarki Wodnej; Mity i złudzenia ochrony
przeciwpowodziowej; Konferencja "Zagrożenia powodziowe w
zlewniach górskich", Bielsko-Biała, 1997
4. E. Bobiński, J. Żelaziński; ekspertyza: Ocena przyczyn lipcowej powodzi na Odrze - wnioski
do programu ochrony przeciwpowodziowej w przyszłości, 1997
5. O. Schaff, Flood Protection in Cologne; Międzynarodowa Konferencja "Ochrona miast przez
powodzią"; Kraków 1995
6. J. Jurand; Oddajmy rzece co jej; "Gazeta Wyborcza" 19 sierpnia 1997
7. T. Walkowicz; Dlaczego należy chronić lasy łęgowe; Spór o Sołę 1996
8. S. Twardy, T. Szymczak, M. Kostuch; Instytut Melioracji i Użytków Zielonych w Faletach; Wpływ
czynników klimatycznych na kształtowanie się odpływów w małych
zlewniach górskich; Konferencja "Zagrożenia powodziowe w
zlewniach górskich", Bielsko-Biała 1997
9. L. Woźniak, Akademia Rolnicza filia w Rzeszowie; Kij w mrowisko; "Raj" 1995
10. J. Adler, Troubled Waters, "Newsweek", 26 czerwca 1996
11. E. Joseph-Tomaszewska; Przedsiębiorstwo Projektowania studiów, usług i realizacji
TERPLAN Sp. z o. o. Katowice; Dolina Soły w Oświęcimiu - walory, zagrożenia i szanse podniesienia atrakcyjności miasta; Spór o Sołę 1996
12. "Die Welt", 4 stycznia 1990
13. W Jankowski; Instytut Ochrony Środowiska we Wrocławiu; Techniczne sposoby wzbogacania wartości
przyrodniczej rzek i ich dolin; Ochrona przyrody i środowiska w dolinach nizinnych rzek Polski; PAN 1996
14. E. Bobiński, J. Żelaziński; ekspertyza; j. w.
15. E. Bobiński, J. Żelaziński; Instytut Meteorologii i Gospodarki Wodnej; Czy można przerwać błędne koło
ochrony przeciwpowodziowej?; "Gospodarka Wodna", nr 4.
source: ZB 8/97
GB No. 1(24)/97 | Contents