Table A. 5. 



257 



Mean Sea Level Rise and Mean Increase of High Water, Low Water, 

 and Tidal Range in cm per Century Over the Period 1901-1986 



No regular trend. 

 **Over the period 1933-1986, because of the closure of the Zuider Sea in 

 1932. 



the high water level, the low water level, and the tidal range. The 

 relative mean sea level rise along the Dutch coast fluctuates between 10 

 and 22 cm per century. In the north of Holland the mean sea level rise is 

 less than in the south, which agrees well with the known tilting of this 

 region, due to the glacial rebound of Scandinavia. 



It can be seen from Table A. 5 that not only the mean sea level but 

 also mean high and low water and mean tidal range are changing. So for our 

 dikes we have to deal with a rise of 19 to 33 cm per century (rise of high 

 water) instead of the 10 to 22 cm rise of mean sea level per century. The 

 different rise of mean high and low water is due to an increasing tidal 

 range. The increase of tidal range can partly be explained by dredging and 

 harbour works. Due to sea level rise the tidal range changes, but only in 

 a minor way (less than 3 cm per century, assuming 20 cm sea level rise per 

 century); see also the next section. This means that a part of the 

 increase of the tidal range cannot be accounted for with our present 

 knowledge . 



It is not surprising that the Dutch coast as a whole has been eroded 

 due to the sea level rise and the increase of tidal range, shown in the 

 previous section. This does not mean that the coast is eroding everywhere; 

 at some locations the coast is even moving seaward. Places along the coast 



