The bedrock topography for the eastern Niagara Peninsula of Ontario and for adjacent areas of New York was reconstructed using more than 7,600 well records and geophysical data. This topography reveals an elaborate system of buried channels dominated by three main passageways connecting Lake Erie to Lake Ontario. These channels are the Erigan, Crystal Beach, and St. Davids. The Erigan, with a depth near 150 ft below Lake Erie water level, precludes the existence of a lake in the Erie basin. North of the Niagara Escarpment, the Erigan channel bifurcates into three outlets that extend into Lake Ontario. The extensive widths and differences in elevation of the outlet valleys suggest that the Erigan channel was active at least three times. Elevations in two of the outlets indicate that water levels in the ancestral Lake Ontario were similar to those of the present-day lake. The third outlet requires water levels at least 30 ft lower than present conditions.

The Crystal Beach channel originates west of Buffalo and trends north along part of the present-day course of the Niagara River. At Niagara Falls, it changes to a southwesterly direction to join the Erigan channel near its southern end. The Crystal Beach system received inflow from Lake Erie through at least 4 inlets with bed elevations only 10–30 ft below the present Lake Erie water level. This suggests the existence of an ancestral Lake Erie similar to present-day conditions.

Limited retreat in the waterfall of the Erigan channel indicates that during the active period of the Crystal Beach and Erigan drainage systems, only the Lake Erie watershed emptied through the Niagara Peninsula. The Upper Great Lakes may have drained through the buried Laurentian valley between Georgian Bay and Lake Ontario.

Drainage of the Upper Great Lakes through the Niagara Peninsula may have first occurred through the St. Davids buried channel. The limited retreat of the St. Davids waterfall suggests a history of only a few thousand years. Its channel above the Niagara Escarpment probably occupied part of the bedrock depression formed by the Crystal Beach drainage system, but at a higher elevation.

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