(b) Bluff recession - the amount of horizontal retreat of the 

 bluff face (as used in this report; Davis, Fingleton, and Pritchett, 

 1975; and Davis, 1976). This generally coincides with the movement of 

 the bluff crest. In keeping with the convention used in the two pre- 

 vious reports, the term bluff recession implies a negative (landward) 

 movement of the bluff. 



(c) Bluff toe - the point of intersection between the steep bluff 

 and flatter beach. 



(d) Waterline - the point of intersection between the lake and the 

 beach at any given time. This feature changes with lake level. 

 Watevline ohange refers to the movement of the feature between two 

 surveys. 



(e) Shoreline - the point of intersection of the profile line with 

 a constant vertical datum such as low water datum (LWD). Shoreline 

 change refers to movement of the shoreline. 



Note. — Positive values of shoreline and waterline change indicate 

 lakeward movement of the features; negative values, landward movement. 



(f) Beach width - the distance between the waterline and the bluff 

 toe during any one survey. 



(g) Foreshore - steep active part of the beach adjacent to the 

 lake. 



(h) Backshore - flatter, less active section of the beach between 

 the bluff toe and the foreshore. May be almost nonexistent on narrow 

 beaches. 



(i) Profile volume - the volume per unit length of shoreline of 

 the profile cross section above the vertical datum and lakeward of 

 some horizontal point. Volume change refers to the change in profile 

 volume between two surveys based on common vertical and horizontal 

 bounds. 



(j) Erosion - the removal, by the action of natural forces, of 

 material (negative volume) from the profile or from a section of the 

 profile, e.g., bluff or beach. Similarly, accretion is an increase in 

 volume (positive volume). 



III. STUDY AREA 



The 17 profile lines on the eastern Lake Michigan shoreline (Fig. 2) cover 

 approximately 310 kilometers with an average spacing of 19 kilometers between 

 lines. As indicated in Davis, Fingleton, and Pritchett (1975), profile sites 

 were selected according to location, year-round accessibility, and their vari- 

 ety of coastal morphology and composition. Because of the glacial origins of 

 the Lake Michigan basin, the geology is complex and highly variable along the 

 shore. Consequently, each profile line has a unique combination of beach 

 type, bluff composition, bluff height, wave climate, and shoreline 

 orientation. General characteristics of each profile line are given in Table 

 1. Figure 4 shows the general shape of each profile line and the changes 

 which occurred during the final study period. 



10 



