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Evaluation Of The Impact Of The 1997 Flood Event On The Baltic Sea
Workshop Participants
(Source: Pro Memoriam from the HELCOM Scientific Workshop on the Effects
of the 1997 Flood of the Odra and Vistula Riversl2-14 January 1998, Hamburg, Germany)
1. Development in the rivers
The meteorological situation in Central Europe was unusual for mid-summer. A stationary
low over Poland transported humid air from the Mediterranean Sea to the north. Passing the
mountain chain in North Bohemia and South Poland the air lost much of its humidity in three
successive rain events. The first rain saturated the soil with the consequence, that the
continuous precipitation ran off on the surface and caused flood waves within the drainage
area of the upper Odra and Vistula rivers (cf. the attached map).
Besides the meteorological factors, deficits in natural and artificial reservoirs and difficulties
in managing the water played an important role in the development of the flood. Therefore,
the flooding of the Odra river banks occurred. The middle and the lower course of the Vistula
river were able to handle the volume of water.
In the Vistula water level gaugings showed two successive flood waves. Maximum flow rates
at the mouth of Vistula (station Kiezmark) were 3700 m 3 /s, average flow rate during the flood
period was about 2500 m 3 /s over more than 1 month. The rates did not exceed Mean High
Flow for the period 1951 - 1990.
In the Odra water level gaugings showed two successive flood waves. Maximum flow rates
estimated by different institutions showed diverging rates from 2700 m 3 /s up to 3400 m 3 /s at
the outflow of the river into the estuary (station Krajnik). Flow rates exceeded significantly
the rates ever observed. Due to the difficulties in estimating flow rates accurate values for
total discharge are presently not available.
Nutrients were mainly supplied to the river water by river bank sediments, by flooded
industrial plants (fertilizer industry), by municipal wastewater treatment plants, as well as by
drowned farms and farm lands.
Metals were mainly supplied by contaminated river and river bank deposits, by flooded
industrial areas, especially in the Katowice-Olkusz and in the Lubin-Glogow regions.
Organic contaminants were mainly supplied by contaminated river and river bank deposits,
by flooded industrial chemical plants, by municipal waste disposals, by drowned agricultural
areas, as well as by flooded fuel storages.
2. Development in the Szczecin Lagoon
The Szczecin Lagoon is the transition zone between the Odra River and the Baltic Sea. Most
of the water (about 75%) discharges to the Pomeranian Bay by the Swina Strait. About 15%
of the water reaches the Baltic Sea via the Peene Stream and about 10% of the water flows
over the Dziwna.
