Interesting, that old 'dip in the road' was where Walmsley Brook used to flow (no doubt for large storms that would have exceeded the culvert capacity under Eglinton). The creek's entire 400 hectare watershed has now been piped and the overland flow system has been blocked off (including recently by development east of Laird). Chronic basement flooding in Leaside and other Toronto neighbourhoods has been linked to the loss of these overland flow paths - basically, during extreme storm events overland flow will continue to pool into low lying windows well and walkouts along the flow path. That water eventually gets into floor drains connected to the sanitary sewer system and soon the entire street or neighbourhood has sewage back-ups. The emerging terminology for this is in the insurance industry is 'concurrent causation' - its a pain because the back-up peril is insured but the overland peril is not, yet one condition affects the other.
So the brook is lost but its function is not. This enclosure of creek systems was the standard grading and municipal servicing practice up to the mid 1980's in Canada when preservation of the 'major' storm overland flow system to complement the 'minor' storm underground system became common. Intensification in Canada's urban centres often results in blockage of major flow paths, generally because the development occurs in a site plan or as a building permit, and not as part of a holistic assessment of the neighbourhood's drainage patterns and needs. Typically a developer's consultant matches grading at the property boundaries and is free to block off a lot of the rest, which can include the overland flow path through the site.
An example of the infilling of Walmsley Brook further downstream is shown on the attached images. Top left is Eglinton and Bayview where the dip in the road was at the old creek crossing in the early 19th century.
The plan shows the old alignment and the extensive flooding experienced upstream and the air photo obliques show where development has blocked off the old flow path.
Detailed analysis correlating the overland flow paths with flood locations in Toronto from May 2000, August 2005 and July 2013 storms is on my blog:
http://www.cityfloodmap.com/2015/08/toronto-overland-flow-factors-affect.html
Blocking off overland flow paths creates a 'flood by a thousand plugs'. Let's hope the site design at Sunnybrook Plaza respects the flow path of the old brook.