230 Long Waves in Canals and Standing Waves in Closed Basins 



velocity and direction, all at the place where the effect was observed. Such 

 methods are largely statistical in kind and require large numbers of observa- 

 tions to give any kind of precise average effect, and large enough to include all 

 variations in direction and velocity of wind. Thus, it is possible to find for a coast 

 the most effective winds for raising sea level. Such investigations of a more 

 statistical nature have great practical value, as they are the basis for most 

 storm warnings. These studies were mainly concerned with the relations 

 between the generating factors, mostly of meteorological nature, and the 

 changes in water level, without dealing with the actual causes of storm surges. 

 This method of investigating well-developed, single cases was used by Dood- 

 son (1929), in the tabulation of storm surges in the North Sea by Corkan 

 (1948) and in the Summary by Doodson (1947). Two especially strong storm 

 surges in the North Sea, namely those of 8 January 1949 and 31 January/ 

 1 February 1953, were investigated by Corkan (1950) and Rossiter (1954), 

 who associated the changes in water level with the passage of atmospheric 

 disturbances. 



As to the theoretical part of the problem, the reader is referred to the 

 previously treated relations between the water level and currents in more 

 or less closed water-masses and the atmospheric disturbances at the surface. 

 These relations form the basis for explaining the occurrence of storm surges. 

 We wish to call attention to the work of Goldsbrough (1954), treating the 

 wind effects on the motion of the sea in an infinite channel and in a rectangular 

 gulf. The basic equations are the equations of motion with the Coriolis force, 

 vertical and lateral friction and the equation of continuity, which can be 

 solved by considering the conditions valid at the boundary of the channel, 

 using infinite series. The results will show only by solving numerical examples. 

 The case of a channel closed at one end is of special interest, in that the 

 dimensions used are an approximate representation of the North Sea. The 

 effect of a transverse and a longitudinal wind, i.e. of a west-east and a north- 

 south wind in the case of the North Sea, has been investigated. Table 28 

 gives the surface disturbances at the east and west ends of the southern shore, 

 the last two columns give the corresponding surface disturbances in the north 

 where the effects of the southern boundary are evanescent. A transverse wind 

 is much more effective than a longitudinal wind in producing a surface dis- 

 placement. It has to be mentioned that the surface disturbance at any point 

 diminishes in magnitude with increase in depth, for the same wind strength. 



Thus, the following is to be expected: near the southern end of the sea 

 a westerly wind always provides a depression on the English shore and rise 

 on the Continental shore. But in the north, where the effect of the southerly 

 boundary on the motion has disappeared, the displacement depends for both 

 sign and magnitude on the depth. Northerly wind produces a depression on 

 the English shore near the southern end and a rise farther north when depth 

 is 20 or 60 fathoms, but gives the reverse effect at 40 fathoms. 



