COASTAL CHANGES, EASTERN LAKE MICHIGAN, 1970-73 



by 



Richard A. Davis } Jr. 



I. INTRODUCTION 



Each time lake levels rise in the Great Lakes system there is appar- 

 ently a corresponding increase in coastal erosion, and thus in property 

 damage and loss. Coincident with these phenomena is an increase in con- 

 cern by coastal residents and officials at all levels of government. 

 Unfortunately, this concern generally diminishes as lake levels subside 

 and coastal areas stabilize. As a result, there has been limited long- 

 term planning or research associated with these periodic problems which 

 directly or indirectly affect several million people. 



A systematic monitoring of three beach locations in southeastern Lake 

 Michigan was begun during June 1968 (Davis, 1972). These sites were sur- 

 veyed and beach sediment was collected every 2 weeks. After more than a 

 year of collecting these data it became apparent that coastal erosion was 

 increasing and that this was coincident with rather rapid rises in lake 

 level. These factors suggested that a widespread monitoring program 

 along the eastern coast of Lake Michigan might serve as the basis for 

 both determining the specific causes of coastal erosion and predicting 

 patterns of erosion during periods of future lake level changes (see Davis', 

 Fingleton, and Pritchett, 1975). 



After nearly 2 years of profile surveys it became apparent that there 

 were few, if any, patterns in the erosion rates, both with respect to time 

 and space. It was necessary to expand the investigation to include the 

 nearshore topography and a long-term aerial photo study. Nearshore topo- 

 graphy was included because of the probable local effects in sedimentation 

 caused by sandbars controlling the energy reaching the beach. The aerial 

 photos were studied to determine if the locations being surveyed had re- 

 acted in a similar manner during previous periods of rising lake level. 



This report summarizes the field observations and the aerial photo 

 study, covering a 3-year period ending August 1973. The report supple- 

 ments Davis, Fingleton, and Pritchett (1975) which contains a discussion 

 of the first 2 years of profiling, a compilation of profile data for those 

 2 years, aerial photos of the 17 profile sites, and preliminary profile 

 bench mark information. 



1. General Coastal Geology and Morphology. 



The study area is along the eastern coast of Lake Michigan between 

 Point Betsie in the north and Lakeside in the south (Fig. 1; Table 1). 

 This coastal area is underlain by Pleistocene glacial drift and character- 

 ized by reworked glacial drift which may take the form of dunes, lake or 

 estuarine sediments, or beach sediments. No bedrock is exposed along the 

 study area. Two aerial photos, along with pertinent geomorpho logical data 



