The shoreline is the intersection of the beach with the Stillwater 

 surface or, if specified, some other datum (e.g., 176.33-meter shore- 

 line) . The relative elevation of the Stillwater level can change with 

 time. Submergence causes the shoreline to retreat by direct encvoaahment 

 of the water over the land. Wifhdrawal of the water during emergence 

 advances the shoreline. 



Total horizontal migration of the shoreline can be more or less than 

 that caused by encroachment, depending on whether erosion or deposition 

 prevails at the shoreline. The lateral migration of a specified aontour 

 is referred to as progradation if the contour moves toward the center of 

 the basin, and as reoession if the contour moves away from the basin. 

 Shoreline retreat (Fig. 5) is thus an inclusive term referring to the 

 total landward horizontal shift or the algebraic sum of encroachment (a 

 function of submergence) plus recession (a function of erosion) . Shore- 

 line retreat implies that either local recession or encroachment has 

 occurred, but is unspecific as to which (or both) is responsible for the 

 landward shift in shoreline position. 



.Retreot 



'Profile adjusted to Submergence [j)^ 



Initial Profile'"^ 



Figure 5. Terminology of retreat. Retreat 



encroachment + recession 

 encroachment = AZ cot a . 



In geology, the terms transgression and reoession have definitions 

 closely related to those discussed above. In fact, these terms were used 

 by Hands (1976) to mean exactly the same thing as encroachment and with- 

 drawal. The reason for substituting encroachment and withdrawal in this 

 study is to avoid using two terms that sound so similar (recession and 

 regression) in reference to two opposite shoreline changes. The meaning 

 and hierarchy of the terms used in this report are shown in Figure 6. 



IV. DATA PRESENTATION 



Shoreline Retreat, 



Although a simple procedure is used for plotting all shore retreat 

 and recession data in this report, the format is slightly different from 

 the usual method. A short step-by-step explanation is given below to 



