Trends of sea level series over decades have been examined for the United 

 States and elsewhere, in some cases dating back to the beginning of the 

 century (Hicks 1972b; 1978; Gornitz, Lebedeff, and Hansen 1982). In the 

 analysis of long-term data, Hicks (1972b) found that series exhibited yearly 

 variability and apparent secular trends, which might either be nonperiodic 

 phenomena or segments of very long oscillations. Yearly variability is due to 

 variations in the meteorological and oceanographic parameters of wind, direct 

 atmospheric pressure, river discharge, currents, salinity, and water 

 temperature. In one case, extreme unidirectional change was caused within a 

 few months by the Alaskan earthquake in 1964 (Hicks 1972a). Apparent 

 secular trends result from longer term glacioeustatic, tectonic, climatologic, 

 and oceanographic influences. 



In some cases, it is important to dampen the effects of yearly variability so 

 that the nature of secular trends will become more pronounced. A weighting 

 array may sometimes be applied to reduce yearly effects. Least-squares 

 regression methods are typically inadequate, as the secular trends often show 

 pronounced nonlinearity (Hicks 1972b). It is also important to examine 

 periodic effects in the long-term series, such as the 18.6-year nodal period, 

 which Wells and Coleman (1981b) concluded was important for mudflat 

 stabilization in Surinam. In some cases, such as on the Great Lakes, water 

 level changes in conjunction with existing models can be used to predict 

 erosion and changes in the shore and offshore profile (Hands 1983). 



The geomorphic response of the shoreline to sea level rise may follow one 

 of several scenarios. Applicability of the erosional response model or Bruun 

 Rule has been discussed by Hands (1983). The onshore migration or rollover 

 model often applies to barrier coasts where washover is an important process 

 (Dillon 1970). In other locations where coastal forms change slowly, features 

 may drown in place without transport occurring (Carter 1988). Depending on 

 the location and time scale involved, the geomorphic effects can be studied 

 with a variety of techniques including historic data, seismic data, and strati- 

 graphic methods. 



Currents 



Speed and direction of longshore and cross-shore currents are also impor- 

 tant for understanding coastal changes. Direct measurements of the velocity 

 and direction of current flow can be made by instruments deployed on the 

 bottom or at various heights in the water column. Lagrangian methods such 

 as floats, bottom drifters, drogues, and dye are also used, especially in the 

 littoral zone where current meter data (as well as the current meters) are 

 adversely affected by turbulence. 



Current measurements may be Lagrangian, following the motion of the 

 flow in its spatial and temporal evolution, or Eulerian, defining the motion at 



Chapter 4 Investigation of Environmental Factors 



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