GB No. 1(24)/97



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.

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.


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.





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).




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.


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.




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


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




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.

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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
  8. 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
  9. 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.
  10. 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
  11. 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
  12. 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.
  13. 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.
  14. 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.
  15. Because of the above fact we propose some ideas of work which should be done.

15.1 Technical method:

15.2 Non-technical methods.15
A. Administrative and legislative procedures

B. Operational work

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