EVALUATION OF POTENTIAL USE OF VEGETATION FOR EROSION 

 ABATEMENT ALONG THE GREAT LAKES SHORELINE 



by 



V.L. Hall and J.D. Ludwig 



I . INTRODUCTION 



The present physical characteristics of the Great Lakes shores in 

 the United States resulted from natural changes in the Great Lakes 

 region since the glacial recession and from the man-induced developments 

 of recent years. The shore varies from high clay, shale, and rock 

 bluffs, to lower shores of rock, sandy beach, and marsh. Except where 

 bedrock is already exposed or protective works have been constructed, 

 the shores of the Great Lakes are being altered by water and wind 

 erosion. 



Wave erosion is the most severe type of erosion occurring along the 

 open shores of the Great Lakes. Damage from wave erosion has been more 

 pronounced since lake levels have risen, the result of recent increases 

 in rainfall over the Great Lakes basin. The average annual rainfall 

 from 1900 to 1972 for the basin was about 32 inches; since 1964, how- 

 ever, the annual rainfall has been above that 72-year figure (Inter- 

 national Great Lakes Levels Board, 1973, 1974). 



Surface runoff, the second most prevalent type of erosion along 

 the Great Lakes shores, is most destructive on steep, unprotected 

 slopes. If protection is inadequate, gullies form rapidly. A related 

 problem, seepage, causes slumping, which increases the erosion rate and 

 probability of landslides. 



Other agents of lesser concern causing shoreline erosion are 

 freezing and thawing and the action of floating ice. Freezing in- 

 creases the volume of water and thawing reduces the volume; the expan- 

 sion-contraction process can move soil or rock sufficiently to cause 

 landslides or rockfalls. In addition to the displacement from freezing, 

 thawing may also cause an unstable layer to form between the ice and 

 substrate, thus increasing the tendency toward bank failure. 



Floating ice has a variable effect on shore erosion. Driven ashore 

 by strong winds, it can cause extreme land scouring. On the other hand, 

 ice may move onto shore and form a protective barrier against wave 

 action that would otherwise erode the shore. 



Wind erosion, normally a dry-weather phenomenon, occurs around 

 Great Lakes dune areas that are droughty and barren. Wind is espe- 

 cially destructive in dune areas, blowing sand inland. The deposited 

 sand may bury established vegetation and perhaps develop a new dune area. 



