Breaking point: its only a matter of time before erosion blows a hole through the Toronto Islands

Of all the sights to see on Toronto Islands, Gibraltar Point stands out. Its perch on the southwestern corner of.

Of all the sights to see on Toronto Islands, Gibraltar Point stands out. Its perch on the southwestern corner of the Islands also makes it the most vulnerable to wind and waves.

So, when the worst flood waters in modern recorded history came in May, Gibraltar Point was among the worst hit, just as it had been in previous floods dating back decades. Gibraltar Point, in fact, has been ground zero in the Toronto and Region Conservation Authoritys (TRCA) efforts to save Toronto Islands from disappearing into Lake Ontario since 1972, when a storm knocked out water supply lines to the city and rapid erosion of that part of the shoreline was identified as a disaster waiting to happen.

But while the fallout helped stir political discussion, successive city councils have largely ignored the danger posed by erosion, opting to fund failed short-term solutions starting in the mid- to late 1970s.

Thats when the Toronto Harbour Commissioners installed a beach building device known as a sand grabber, as well as 350 metres of gabion baskets in an attempt to stabilize Gibraltar Point. They failed a few years later.

The Toronto Islands are washing away

The TRCA has been warning since it authored a seminal report in 2008 that if something wasnt done to contain erosion at Gibraltar Point immediately, it would only be a matter of time before Lake Ontario blows a hole right through to the Islands inner lagoons, taking sensitive wetlands and habitat with it.

Money and politics

Theyre the reasons the former Metro Council wanted to level residential properties on the Islands and turn the area into green space in the 50s, primarily so it could save the expense of clean up every time a storm blew through to wreak havoc, of which there have been many over the decades. Theyre also the reasons erosion problems have been disregarded for so long, despite evidence dating back to 1983 when a Harbour Commission study revealed that wind and waves were contributing to the washing away of up to eight metres of coastline per year along Gibraltar Point. A shoreline management study in 1994 predicted that nearly one million metres cubed of soil (about 500 Olympic-sized swimming pools) would be lost by 2043 at Gibraltar Point alone.

Too little too late

It was only after a severe storm in 2004 flooded the Gibraltar Point washroom and put at risk a number of structures in the area, including intake lines leading to the Toronto Island Filtration Plant and a water main that provides the only potable water to the Island Yacht Club and Island Airport (not to mention supplies the Island fire department) that the city asked the TRCA to develop a long-term strategy to stem the growing tide of erosion.

It became clear early on in that evaluation process that any measures implemented would have to protect not only Gibraltar Point but the Islands themselves.

A number of options were considered to stabilize the shore, including a very expensive one to bring in sand to raise the levels of the Islands.

But breakwalls and beach nourishment were considered the most economical way to go. Emergency work led to the building of a rock wall to Gibraltar Point. But erosion continued.

The impact of human activity

Much of the dune system from Gibraltar Point to the Island Airport has been vulnerable to erosion since the 80s, but human activity from visitors to Hanlans Point Beach has sped up shoreline deterioration.

Without a sand management program to replace lost sediment, TRCA predicts the dunes will eventually disappear. The fallout is already being seen with the loss of wetlands and wet meadow habitat and reduced water depths along Hanlans Beach and the Western Gap as sediment from the dunes is washed back into the lake.

Wild card

Gibraltar Point and nearby Hanlans Beach make up the largest continuous habitat on the Toronto Islands, containing Cottonwood woodlands that support one of North Americas largest bird populations, including the rare Northern Saw-whet owl. The 260 species of birds that have been identified in the Toronto Bay area rely on the areas wetlands for habitat. Some 34 wetlands cover a sixth of the Toronto Islands total area, some 50 hectares, which is both a blessing and a curse, considering the current rate of erosion along the shoreline that threatens most of it.

Enter Sandman

A sand management plan that involves dumping some 20,000 metres cubed of sand per year along the shore and nearshore of Gibraltar Point was recommended as the preferred option by TRCA. But adding to the complex of issues is something called nearshore down-cutting, a process taking place underneath Gibraltar Point, which is lowering the Islands bottom profile. No amount of local remediation efforts may be able to stop that from continuing. | @enzodimatteo

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