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15 10 5 5 10 

 ENCROACHMENT WITHDRAWAL 



15 (m) 



( due to rising water ) ( due to falling water ) 



Figure 11. Encroachment versus recession as a cause of shoreline retreat. 

 The total retreat of the shore is the sum of encroachment by 

 the higher waters plus recession of the beach. Given only the 

 initial profile shape, the encroachment that would result from 

 different water level changes can be predicted exactly. Re- 

 cession would be more difficult to predict, and though sometimes 

 neglected, recession was by far the more significant of the two 

 components contributing to retreat on the sandy lake shore. 



26 



