Introduction 
7 
1. Introduction 
1.1. Background 
Extreme oscillations of coastal sea levels pose a 
threat to the national economy and ecology of 
many countries. Considerable technical and sci 
entific effort has been invested worldwide to 
reduce the impacts of such phenomena, which 
may reach catastrophic proportions. Storm 
surges are water level extremes which have been 
investigated quite extensively because they 
represent a major threat to the coastal popula 
tion. By contrast, the existing body of research 
on extremely low water levels, so-called negative 
surges, is much smaller. As negative surges may 
cause small harbours to fall dry and obstruct 
navigation in general, an understanding of nega 
tive surges is crucial to the safety and efficiency 
of navigation. Future ships will be larger and have 
deeper draughts, and sailing times to and from 
harbours will be reduced further in order to save 
costs. Also the loading rate is a very important 
factor for shipping companies. Ferry traffic of 
course depends on water levels, and shipyards 
need enough water for docking and undocking. 
To ensure the safety of navigation in the difficult 
waters of the southern Baltic Sea, reliable water 
level data are essential, particularly in case of 
negative surges. 
The present study of negative surge events in the 
western and central parts of the southern Baltic 
Sea coast has been prepared by the Polish/ 
German W-1 Group on Hydrology and Hydro 
geology in the Polish/German boundary waters 
and is a sequel to a co-operative study of histo 
rical storm surges that have occurred on the 
same coast, which was completed in 2005. How 
ever, the period covered by the present study is 
five years longer than that of the first study. The 
project was implemented jointly by Bundesamt 
fur Seeschifffahrt und Hydrographie Hamburg - 
Rostock (BSH), Germany, and Instytut Meteor- 
ologii i Gospodarki Wodnej, Oddziat Morski 
(IMGW-OM), Poland. 
In the first part of the monograph, the phenome 
non of negative surges in the western and central 
parts of the southern Baltic Sea coast is ana 
lysed for the period 1955-2005 using historic 
records of gauge stations along the German and 
Polish coasts. A compilation of all negative 
surges recorded at selected water gauges is pre 
sented, complete with a statistical analysis of the 
parameters contributing to their occurrence. The 
second part contains detailed descriptions of the 
twenty most dangerous negative surges recorded 
in the above period, in each case outlining the me 
teorological situation and describing the impact of 
atmospheric conditions on coastal sea levels. 
1.2. Brief review of scientific con 
tributions 
Of all publications dealing with sea level changes 
in the Baltic Sea, that of E. Lisitzin [1974] is the 
most important one. Several papers have been 
published to date which discuss extreme water 
level changes in the Baltic Sea [Majewski 1983, 
1961, Stanislawczyk 2001, Sztobryn 2005] or ana 
lyse the impacts of dangerous weather situations - 
atmospheric circulation disturbances, steep 
pressure gradient and strong wind force - on sur 
face water oscillations at the coast [Stanislaw 
czyk 2002, Wielbinska 1964]. Unlike storm 
surges, which cause rising water levels on the 
coast, negative surges causing water levels to 
fall have been dealt with to a much lesser extent. 
Few papers have been published on this subject 
[Majewski 1985, Stanislawczyk 2001,2003, 
Sztobryn 2001, Wroblewski 1970], among them 
“The low sea levels in the Baltic Sea” which dis 
cusses general characteristics of low sea levels. 
The most comprehensive study of negative 
surges along the Polish coast so far is that of 
Majewski and Dziadziuszko [1985]. 
The authors investigated negative surges in the 
period from 1951 to 1976. In most of the more 
recent studies, negative surges have been dis 
cussed only in the context of water level fluctua 
tions in general. The most important recent 
projects are “Studies and Modelling of Severe 
Hydrometeorological Conditions Along the Polish 
Coast” (Project ERB CE PDCP 925076 in con 
nection with the SELF project) and “Forecast of 
Extreme Sea Levels by Artificial Neural Network- 
Western Coast of Poland” (Project 3T09003/200/98 
of the Scientific Committee of Poland). 
Three main factors account for the occurrence of 
negative surges on the coast of Poland: wind, the 
inverse barometric effect, and the filling level of 
the Baltic Sea. The general atmospheric condi 
tions leading to extreme water levels are known 
in principle. 
Negative surges on the coast of the German 
Democratic Republic in the period from 1900 to 
1980, also including those on the Danish coast, 
were investigated by Schmager (1984). 75 storm- 
triggered negative surge events occurred during