262 



It is clear that one must be careful with the interpretation of short 

 time series of coastal erosion and accretion. This is especially the case 

 when the phenomenon of "Sand Waves" is important along a certain part of 

 the coast. Along the Dutch coast there are major sand waves moving along 

 the southern and the northern part; along the central part the sand waves 

 are rather small (Kohsiek, 1988) . The sand waves migrate to the north in 

 the southern and central part and to the east in the northern part. The 

 amplitudes on the Wadden Islands vary between 10 and 1200 m, while the 

 migration speed varies between 220 and 450 m per year, e.g., the sand waves 

 moving along the northwestern part of the island Schiermonnikoog have a 

 period of about 30 years and an amplitude of about 300 m (Fig. A. 8). Along 

 the central part, amplitudes are 25 to 50 m and migration speed is 30 to 

 100 m per year. In the southern part of the Dutch coast, the sand waves 

 have amplitudes between 25 and 200 m and migrate 30 to 300 m per year. 



Impacts of Sea Level Rise on the Netherlands 



Due to the greenhouse effect, mean sea level along the Dutch coast 

 will rise more rapidly in the coming century than in the recent past. In 

 this presentation a certain rise (in most case 1 meter) in sea level over 

 the next 100 years is chosen in order to investigate the possible impacts 

 of future sea level rise in the Netherlands. The results presented herein 

 are a summary of a Dutch report entitled "Zeespiegelrijzing - Worstelen met 

 wassend water" (de Ronde et al . , 1986). 



A sea level rise of 1 meter or more has serious implications for: 



* Safety of dikes and other defense structures along the coast and the 

 lower parts of the main rivers. 



* Morphology of dunes, shore face, and estuarine systems. A critical 

 issue is whether the bed can rise as fast as the sea level rises. 



* Stability of ecosystems. How will vegetation and animal life change 

 with sea level rise? The Wadden Sea is of great importance for North 

 Sea fish and migratory birds. 



