Baltic storm floods

In the Baltic Sea which water level is referred to as a storm flood and how often did this occur in the recent past?
Wolfgang Althof, Rostock, by e-mail

In the Mare Balticum, the Federal Office for Shipping and Hydrography speaks of storm floods, if the water level is higher than the mean sea level by one to 1.5 meters. Levels from 1.5 to two meters above the norm are referred to as severe storm flood. If the water masses are even higher, then the coastal population have to deal with a very severe storm flood. As on the 13th November 1872 when the level on the Baltic coast in Schleswig-Holstein rose up to 3.30 meters above sea level (NN).

Interestingly, the authorities in Mecklenburg-Vorpommern have a different set of standards with regard to measures for civil protection. On the outer coastal area a plus of 1.71 while in the inner coastal areas a plus of 1.31 meters are referred to as servere storm floods. "For example within a time period of about 100 years there were 15 cases in Wismar, eight cases in Warnemünde and seven cases in Greifswald of storm floods with peak values of above 1.50 above the normal sea level", is reported in a coastal protection report for Mecklenburg-Vorpommern: "On average Wismar was afflicted by a very severe storm flood every seven years, Warnemünde every 12.5 years and Greifswald every 14 years."

A systematic overview on the Baltic Sea storm floods during the last decades will probably be available to the general public shortly under www.bsh.de on the web sites of the Federal Office for Shipping and Hydrography.

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