120. Wood (1978) discusses perigee-syzygy and the occurrence of coastal 

 flooding (when coincident with strong, persistent onshore winds) associated 

 with the reduced lunar distances during perigean spring tides. Wood attrib- 

 utes this to the reinforcing effect of the alignment of the sun and moon's 

 gravitational forces on the earth and gives many examples of the effects this 

 may have on the coast. This perigee-syzygy alignment, Wood states, may cause 

 tidal flooding within a period of 1 to 3 days following (or in some few cases, 

 a day or so preceding) the mean phase or epoch of the perigee-syzygy align- 

 ment. Tide heights in excess of 100 cm were in fact observed on 16-19 January, 

 17 February, 24 October, and 22-24 November. 



121. The highest tidal heights, though, were not coincident with the 

 perigean alignment but more nearly correlated to strong nonastronomical forces 

 such as persistent onshore winds and high waves. The highest and second high- 

 est water levels observed were 118 cm on 2 March and 116 cm on 5 January, 

 respectively. 



122. The lowest water level observed was -119 cm on 16 March, a time 

 when tides were expected to be higher than normal. A high-pressure system 

 and sustained offshore winds dominated the water level producing forces and 

 resulted in the annual extreme lowest tide height. 



Water characteristics 



123. Temperature . Daily sea surface water temperatures at the seaward 

 end of the FRF pier are presented as a function of time in Figure 22, and the 

 distribution of temperatures is shown in Figure 23. The difference in daily 

 temperatures was greatest during July when a 9° C change was observed over a 

 24-hour period, see Figure 22. This difference is attributed to frequent off- 

 shore winds which blow the warm surface water offshore allowing upward and 

 landward circulation of the much colder bottom water. Onshore winds, on the 

 other hand, reverse the circulation pattern, piling up surface water along the 

 shoreline and creating a seaward return flow along the bottom. 



124. As can be seen in Figure 23, for less than 20 percent of the time 

 during 1980 the water temperature exceeded 20° C, while for less than 10 per- 

 cent of the time the temperatures were lower than 4° C. Seasonal distribution 

 of the temperature indicates the coldest temperatures occurred from January- 

 March, while the warmest were from July-September as might be expected. 



125. The monthly mean sea surface temperatures measured at the seaward 

 end of the FRF pier (see tabulation below) varied in phase with the air 



59 



