“When Dent started the project, Castle Frank Brook rose in three small creeks in the Lawrence and Dufferin area and flowed southeast about 12 kilometres to the Don River south of where the Prince Edward Viaduct now is. The brook was named after Castle Frank, built in 1794 as the summer home and country retreat of Lieutenant-Governor John Graves Simcoe and his family. Situated on a high ridge that Simcoe’s wife, Elizabeth, hoped would ‘secure us from Musquetos,’ Castle Frank afforded a view of both the brook and the river, which met less than half a kilometre from the house at what is now Bayview Avenue and Rosedale Valley Road. Though little surface water can be found today along the stream’s course, its erosive force is manifest in three surviving topographical features. The most northerly is Cedarvale Ravine, the most southerly is Rosedale Valley and between the two lies Nordheimer Ravine.”
The book states that over the 20th century bits of the ravine were buried due to the requirements of water mains. The major changes came in preparation for the proposed Spadina Expressway, when the Spadina South Trunk Drain Sewer was completed in 1970.
“The threat posed by the Spadina Expressway came to an end in 1971, though more cut-and-cover work undertaken for its transportation successor, the Spadina subway, impacted both Nordheimer Ravine west of Spadina Road and all of Cedarvale Ravine.There, the grades were raised and the valley floor flattened, and any semblance of natural water flow was eliminated by 1978.”
Source: Toronto’s Water from Lake Iroquois to Lost Rivers to Low-flow Toilets, edited by Wayne Reeves and Christina Palassio Coach House Press, 2008. Wayne Reeves’ article: “Addition and Subtraction: the Brook, the Ravine and the Waterworks” pp. 122-132