Die Küste, 74 ICCE (2008), 31-44 
Seabed Morphology and Sediment Dynamics 
By Manfred Zeiler, Klaus Schwarzer, Alexander Bartholomä and Klaus Ricklefs 
Contents 
1. Introduction 31 
2. North Sea 31 
2.1 Offshore Waters 32 
2.2 Tidal Flats 35 
2.3 Estuaries 36 
3. Baltic Sea 37 
3.1 Offshore Waters 39 
3.2 Nearshore Zone 40 
3.3 Coast 41 
4. References 41 
1. Introduction 
The German coasts extend along two different seas, the tide-dominated North Sea and 
the intra-continental non-tidal Baltic Sea. While the North Sea has an open transition to the 
Atlantic Ocean, the Baltic Sea has its only connection to the world’s oceans through the 
North Sea and the shallow and narrow Danish straits and sounds (Fig. 1). Both shelf seas are 
not only different in their hydrographic characteristics, but also in their geological develop 
ment (Schwarzer et al., 2008, this volume), their sediment conditions and their geo-morpho- 
logical features. 
Although the seafloor in the German sectors of North and Baltic Sea is built up mainly 
of loose Quarternary deposits, the driving forces leading to environmental changes are quite 
different. While in the North Sea the sedimentological and geomorphological development 
(morphodynamics) is ruled by tides and waves, waves and wind driven currents are relevant 
for the seafloor conditions and sediment dynamics in the Baltic Sea. In both seas, however, 
phases of storm-induced high water levels often lead to severe changes of the coastal geo 
morphological environment. For the German North Sea coast this holds especially for storms 
from (north-)westerly directions, which can induce water levels of up to five meters above 
mean sea level usually for the duration of one or two tidal cyles. For the western Baltic Sea 
coast, storms from north-easterly directions have the strongest influence on coastal changes. 
Here, high water levels and therefore hydrodynamic extremes can last for days (Schwarzer, 
2003). 
2. North Sea 
The German Bight is a meso-tidal to low macro-tidal environment with a tidal range 
between two and four meters. According to geo-morphological features and sedimentologi 
cal environments, the German sector of the North Sea can be divided into the three zones: 
the offshore waters, the tidal flats of the Wadden Sea and the funnel-shaped estuarine river 
mouths (Fig. 2). In the meso-tidal environment, the barrier island chain of the East Frisian as