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Toronto’s majestic cliffs are one of the wonders of our bioregion, but somehow the Toronto and Region Conservation Authority doesn’t have the guts to freeze development even though it’s washing the sandy heights into the lake. See them while you still can.
Natural wonder The bluffs stretch for 15 kilometres along Lake Ontario and in some places tower more than 90 metres above it. But for all their physical beauty, the bluffs have a fatal geological flaw – cliffs of sand and clay are highly susceptible to erosion. Wave action, wind, groundwater runoff and intensive building on tableland up top are causing the crest of the bluffs to retreat by up to half a metre a year. For the Toronto and Region Conservation Authority, it’s become prohibitively expensive to stop the erosion.
Living on the edge More than half a dozen homes have fallen over the bluffs in recent history. Remnants of their foundations can still be seen protruding from the banks at the foot of Birchmount (pictured here) and on nearby Springbank. Provincial policy directs development outside a “hazard zone” 10 metres from the “stable top of bank.” But that hasn’t prompted the Authority to intervene when residents decide to build massive additions to their homes or add tennis courts or swimming pools to their ever-shrinking backyards.
Thar she blows “Blowholes” like these popping up all over the face of the cliff, some triggering mudslides that stretch from the top to the bottom of the bluffs, are a sure sign of rapid erosion. Geotechnical experts say the blowholes are the result of infill development concentrating runoff in bulges at the top and then blowing out of the face of the bluffs.
When the levee breaks The Toronto and Region Conservation Authority has constructed a system of groynes to break waves and slow erosion at the foot of the bluffs east of Birchmount. But other areas of the bluffs have no erosion control save for a few slabs of concrete placed along the shore. There’s also little evidence that the Authority has taken any steps to deal with the erosion caused by wind and groundwater, especially at the top of the bluffs, where little has been done to discourage development destabilizing the banks.
A chunk or slab won’t do ya Other projects to stabilize the bluffs, including the laying of huge slabs of concrete on the slope, have in most cases been undertaken too late to save homes above. The concrete solution also prohibits the growth of vegetation that could help slow erosion. Do we really want a natural wonder littered with concrete?
Sand trap There’s been no comprehensive study undertaken to determine how development at the top of the bluffs – more roofs and pavement mean more runoff – is contributing to overland drainage. But piles of sand like these along beaches at the foot of the bluffs are a bad sign. They suggest that streams of water are carrying sand down the face of the bluffs.
