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Effects Of The 1997 Flood Of The Odra And Vistula Rivers 
Eugeniusz Andrulewicz 1 and Bogumila Kaczorek 2 
'Sea Fisheries Institute 
Department of Oceanography 
Kollataja 1 
81-332 Gdynia 
2 Polish HELCOM Secretariat 
Kossaka 1 
80-249 Gdansk 
Abstract 
The catastrophic flood in the central part of Europe in July and August 1997 affected most of 
the southern part of Poland, in the upper parts of the Odra and Vistula drainage basins of the 
largest Baltic Rivers (Fig. 1). Flood water covered densely populated regions including 
towns, factories, agriculture land, animal farms, chemical storage sites, sewage treatment 
plants, scrap yards, cemeteries, etc. There was also a fear that the Baltic Sea would be 
seriously polluted when flood waves reached the sea. Therefore it was important to undertake 
investigations at the time when flood outflows reached the sea. These studies were 
undertaken by the research vessel r/v „Baltica”. 
An unusually large algae bloom occurred in the open Baltic at the same time as flood water 
discharges, but it appears to have been fueled primarily by the „summer of the century” 
which was unusually warm and dry for an extended period of time. In short, the effects of 
discharges of flood waters were limited to short-term effects in areas near the river mouths. It 
appears that the consequences to the Baltic Sea were minimal relatively to the highly polluted 
condition of waters in flooded areas. 
The amount of self-purification which appears to have taken place suggests that the self- 
purification capacity of these rivers has generally been underestimated. The natural filtration 
capacity of the Odra estuary and the unregulated state of the Vistula River which allows for 
high natural ability for self-purification were the primary factors in mitigating the pollution 
load that reached the Baltic Sea. These processes were further enhanced by the relatively long 
time span before flood waters reached the sea, the spreading of flood waves over a large 
surface enabling sedimentation and photooxidation, and high air and water temperatures. 
Unfortunately the effects of self purification of flood waters were not studied. However it can 
be assumed that a similar flood event occurring close to the sea would result in much greater 
consequences to the Baltic Ecosystem. 
Socioeconomic effects directly and indirectly related to the flooding as well as international 
solidarity and help are highlighted. The discussion of socioeconomic effects is based on a 
more comprehensive document prepared by the Polish Flood Committee. According to the 
recent estimation presented by the Polish Flood Committee and based on Voivodship 
Committee reports, losses due to the flood amounted to 14.450 billion PLN (approx. 4 billion 
USD), including 12.437 billion PLN (approx. 3.5 billion USD) in the Odra drainage area and 
2.013 billion PLN (approx. 0.5 billion USD) in the Vistula drainage area. The socioeconomic 
effects of the flooding will be longer lasting and potentially more profound. Flood waters 
destroyed or damaged many homes and businesses, and flooded agricultural land. The Polish 
government has instituted a special program which provides longer-term assistance to those 
in need.