MONITORING SHORELINE RESPONSE TO LAKE LEVEL VARIATIONS: EASTERN LAKE ONTARIO SHORELINE

The Eastern shore of Lake Ontario consists of a delicate barrier dune system. The beach-dune system is important for recreation and protects wetlands, endangered species, public and private property. Beach erosion is a concern in this area, especially in the southern portion of the system. Beach profiles have been measured at five locations along this seventeen-mile stretch of sandy coastline. Profiles were measured using the Emery technique, beginning at a datum point in the foredune and moving lakeward. These data are required to quantify changes in the shoreline. Earlier workers conducted the profiling in 2000. This study reports on profiling done since fall 2002, which involved monthly measurements from May through November. Snow cover prevents data collection in other months. Generally, lake level rises in the spring and gradually falls at the beginning of the summer through autumn. During the study period two strong wind storms occurred, one in mid October and another in mid November of 2003. These wind storms are capable of altering lake level on the short term due to wind set-up and seiche. Mean grain size generally fines from south to north along the eastern Lake Ontario shoreline. The beach profile at the southernmost location just north of the mouth of the Salmon River is the steepest and has the highest concentration of gravels. Sandy Island Beach to the north is finer grained, but cobbles are commonly deposited on the beach during storms. Gravel-sized sediments are rare at the three northern beaches, and sand bars commonly form in the shallow nearshore zone during the summer months. Comparisons of monthly profiles at each location show progradation of the swash face in the summer and autumn months as the lake levels fall. At some of the northern locations, the sand bars diminished in size as the beach face prograded during the late summer and fall. As lake levels rose in the spring, the swash face shifted landward and steepened. The wind storms did not have an appreciable effect on subaerial sections of the profiles, except for Montario Point; there the base of the foredune was eroded.