48 



example, the bay to have a gentle boundary slope as opposed to a vertical 

 wall- like perimeter would reduce the changes in superelevation and tidal 

 range compared with the vertical wall case (Fig. 4.3). In general, 

 however, it was concluded that due to an increase in sea level, "additional 

 coastal flooding may occur beyond that due merely to the changes in sea 

 level." Observations by Fuhrboter (1986) in the German Bight estuaries 

 seem to corroborate such a trend. 



4.5 RESEARCH NEEDS 



Fast computers with large memory storage have made numerical modeling 

 of tides rather sophisticated. In many cases, it seems, modeling 

 capabilities have "outstripped" data quality such that inaccuracies in 

 collected data limit the accuracy of mathematical prediction. Data 

 limitations arise from many causes; it suffices to note two factors. 



One pertains to a lack of physical understanding, on a microscale , of 

 phenomena which ultimately affect water level prediction. An example is 

 our understanding of bed forms, the manner in which they change with flow, 

 and the precise relationship between their occurrence and the flow 

 resistance they generate. Such forms may be as small as ripples to large, 

 migratory sand waves found in estuaries and in nearshore waters. 



The second factor is related to historic tide records. Many records 

 are highly contaminated by such unaccounted for effects as arising from 

 land subsidence, poor leveling between gages, shifting gage locations, and 

 a general lack of knowledge of the physical surroundings and variations in 

 parameters characterizing these surroundings over the duration of tidal 

 record. Thus, an accurate, quantitative evaluation of superelevation 

 effects would require the deployment of better monitored gages. In 

 addition, Mehta and Philip (1986) noted that our understanding of bay 

 response and its relation to response outside would be considerably 

 enhanced by: 1) establishment of additional primary stations along the open 

 coast, 2) collection of long-term records at several presently designated 

 secondary stations in bays, 3) accurate geodetic leveling connecting 

 additional outside and inside stations, and 4) publication of relevant data 

 in a user-oriented format. National Ocean Service initiated marine 

 boundary programs and tidal datum survey programs appear to be directed 



