29 
8 
North Shields 
•tWick / \ 
Stavanger 
m Aberdeen \ / 
\ \ ° / / 
O max5m 
max8m 
• max5m (t<tmax) 
max8m (t<tmax) 
^Sfumingh 
am / 
Lowestoft / 
\ O Ijmulden / 
\ O TFT 
O Borkum O o Hirtshals 
❖ O Esbjej^ 
^li O Cuxhaven / 
Fig. 5.4.4: Peak water levels at selected sites (input signal: 3 positive signals, T 1800 s, 
H 5 m (dark blue) and H 8 m (light blue), from the north; model: North Sea 2 km). 
5.5 Modification near the coastline 
Near the coastline, it is no longer possible to estimate the modification of simple waves by 
means of analytical solutions to linear equations because this would require the flow of 
mechanical energy and the wave period to be constant during tsunami propagation and 
modification. That applies only as long as the influence of friction is low. In the immediate 
vicinity of the coast, however, mechanical energy is dissipated inhomogeneously and T 
rather is a function of location than of the tsunami generation process (Munk 1962, Sabatier 
1986). 
Fig. 5.5.1 shows the continuation of frictionless simulation. Close to the coast, the wave 
height is of the same order as undisturbed water depth. The propagation velocity thus is 
described more precisely by g{h + rj). In this way, the signal height not only increases with 
decreasing depth, but its front also becomes steeper.