COASTAL GEOMORPHOLOGY AND LITTORAL CELL DIVISIONS ALONG THE ILLINOIS-INDIANA COAST OF LAKE-MICHIGAN

The 156-km Illinois-Indiana coast of Lake Michigan can be divided into three geomorphic areas: (1) the 19-km-long Zion beach-ridge plain alo ng the extreme northern Illinois coast (12 percent total length), (2) the 25-km-long Lake Border moraines bluff coast along most of the nort hern half of the Illinois coast (16 percent total length), and (3) the 112-km-long Chicago/Calumet lacustrine plain along the southern half of the Illinois coast and the entire Indiana coast (72 percent total l ength). Bluffs rise as much as 27 m above the shore in Illinois, and d unes rise as much as 57 m above the shore in Indiana. However, within 1 lan of the shore, 58 percent of the Illinois-Indiana coast is 10 m o r less above mean lake level, and 43 percent is no more than 5 m above mean lake level. Before coastal development, net erosion dominated ne arly all of the Illinois coast. The regional transition from net erosi on to net accretion occurred on the western Indiana shore near present -day Buffington Harbor. The eastern half of the Indiana coast was the zone of net convergence of two littoral transport cells that extended along the entire western and eastern shores of the southern half of La ke Michigan. Coastal development has segmented the Illinois-Indiana co ast into 10 littoral cells bounded by total or near-total barriers to littoral transport. Within these 10 primary cells are a total of 25 se condary cells having partial littoral sediment bypass across the cell boundaries.