Along the southern shore of Lake Ontario, the most prevalent geomorphic types are cohesive and bedrock bluffs. Low banks and gravelly beaches are also common on much of this coastline, with bedrock becoming the dominant feature in the northeastern portion of the lake, near where it meets the St. Lawrence River. A barrier island-dune complex is located between Oswego, New York, and the St. Lawrence River, and Oswego Harbor contains artificial sections of shoreline.
The Canadian coast of Lake Ontario is similar to the U.S. portion, with bluffs and beaches primarily in the western portion and bedrock to the east. The shorelines around the cities of Hamilton and Toronto also feature artificial structures.
Water levels on Lake Ontario are controlled by man-made structures and regulation plans that are determined by the International Joint Commission (IJC). Lake levels are important because they influence how much of the shore is at risk of erosion, the capabilities of navigational harbors and channels, and the composition of wetlands. Thus, shoreline types and changes on Lake Ontario are heavily dependent on anthropogenic controls.