Approximately 10,500 years ago, the water level of Lake Erie rose 3 – 4 meters above its present water level. At this time the Upper Great Lakes drained through North Bay and the Mattawa River, to the Ottawa River into the St Lawrence River Valley. This resulted in the water drainage through the Niagara River being reduced to only 1/10 of its present flow (representing only the drainage of Lake Erie). The reduction of water flow through the Niagara River continued for approximately 6,500 years before the drainage route returned to its previous course through the Niagara River. This water reduction through the Niagara River correlates to the narrowness of the Niagara River Gorge.
Isostatic rebound had lifted the land surrounding North Bay cutting off the out flow of water from the Nipissing Lakes (Upper Great Lakes). The rising waters on the southern shores of Lake Huron breached the Lake Huron moraine and discharged the entire flow into the Lake Erie basin. This new direction of flow was initially shared with an exit at the southern shore of current Lake Michigan. Over several hundred years, the water level of the Lake Erie Basin rose 3 – 4 meters increasing the flow through the Niagara River. This increased flow caused the rapid recession of the Niagara Falls through the gorge south of the current Niagara Glen.
Glacial Lake Agassiz had a great influence on the Lake Erie basin. 11,000 years ago, proglacial Lake Aggassiz initially drained southward over a divide into the Mississippi River basin. As the divide rose from isostatic rebound, the entire flow of the Upper Great Lakes flowed into the Lake Erie basin through the Niagara River.
The increased flow into Lake Erie caused water levels to rise in the basin up to five meters. Water levels of Lake Tonawanda increased accordingly.
Today, the winds can cause the water level in Lake Erie to rise 2 – 5 meters in several hours. Lake Erie is the shallowest of the Great Lakes with an average depth of sixty (60) feet.