Home > TWAHRS > Existing Conditions: Physical Processes & Cultural Influrences
Prior to settlement of the Toronto area, the shoreline was very different from the one we know today. The rivers and creeks supplied clear, cool water and provided habitats for river-spawning fish such as salmon. Nutrient-rich estuaries supported wetlands teeming with wildlife. Sandy spits provided protection from winds and wave action. Sheltered stretches of shoreline were lined with lush stands of emergent vegetation. Much of the nearshore was covered with sand, gravel and stonei.
Forest Clearing
 Colonization of the Toronto watersheds in the late 1700s and early 1800s resulted in profound changes to physical conditions in the rivers and creeks, which in turn affected waterfront habitats, fish and wildlifeii. These changes began with extensive clearing of the dense forest cover that originally blanketed the uplands. As the forest trees and understory plants were removed, and land contours altered by grading, water and sediment runoff to the creeks and rivers increased, resulting in increased flooding and bank erosion downstream. Estuaries and rivermouth wetlands were choked by excessive inputs of sediments
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Sawmills and Gristmills
Numerous sawmills and gristmills were built along the banks of the creeks and rivers. They discharged their wastes directly into the watercourses, resulting in water pollution and siltation of fish spawning grounds. The millponds increased water temperatures, trapped sediments and altered flow regimes. The dams created barriers to fish moving upstream. The native salmon populations that were once plentiful in this area declined rapidly, with the last recorded catch in Toronto Bay occurring in 1874iii.
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Stonehooking
 From 1850-1910, stonehooking — the removal of aggregate materials from the lake bottom for use in construction — was a major force in changing physical conditions and shoreline processes. During this time period, 1 million cubic metres of materials were removed from Toronto Harbour alone — enough to cover the entire waterfront from Etobicoke Creek to the Rouge River with a layer 1 metre thick and extending 25 metres offshore, as shown below. As a consequence of the loss of aggregate materials, large amounts of valuable aquatic habitat disappeared, and the shoreline was exposed to accelerated erosion.
In areas that still have an abundant supply of stone material (eg Northumberland County) it is an important component of the physical structure of the shoreline. The movement of stone material along the shoreline forms bays, points and bars which are critical elements of aquatic habitats, as shown in these two photos.
 
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Shoreline Alterations
Other early shoreline alterations included weed removal, filling of wetlands and small streams, hardening of the shoreline, and channelization of watercourses. Starting in the 1790s, aquatic plants were frequently removed from Toronto Bay because they impeded navigation. A map of Toronto Bay in 1813 shows early shoreline modifications in the form of docks, jetties and filling of small creeks.
By 1913, further alterations included navigable channels such as the Western and Eastern Gaps and the Keating Cut. Ashbridge's Bay at the mouth of the Don River became severely polluted by wastes from the growing Town of York, the Gooderham and Worts Distillery, and associated cattle byres.
Alterations to Toronto Bay, 1813
Alterations to Toronto Bay, 1913
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Toronto and Region Area of Concern
 By 1987, environmental conditions were so badly impaired that the Toronto waterfront was included on the International Joint Commission's list of 42 Areas of Concern around the Great Lakes requiring remedial actioniv. The impairments noted for Toronto's waterfront were:
- Restrictions on fish and wildlife consumption
- Degradation of benthos
- Restrictions on dredging
- Eutrophication and undesirable algae
- Beach closures
- Degradation of aesthetics
- Degradation of fish and wildlife populations
- Loss of fish and wildlife habitat
The key factors contributing to these problems are combined sewer overflows, contaminated stormwater, loss of habitats, and degradation of natural landscapes. In the past 25 years, eutrophication has been reduced, sediment quality has improved, and habitat availability and diversity have been increased, but Toronto remains on the list of Areas of Concern.
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Wet Weather Flow Management Master Plan
The City of Toronto's 2002 Wet Weather Flow Management Master Plan (WWFMMP) provides important direction for ongoing improvementsv. The plan proposes a program totalling $1 billion over the next 25 years, including public education, municipal operations, shoreline management, stream restoration, and control measures at the end-of-pipe, during conveyance, and at the source. The shoreline management proposals include structures at the waterfront, near the mouths of Etobicoke Creek and the Humber River, to deflect ongoing inputs of pollutants away from waterfront beaches. These are proposed because the WWFMMP is limited to the City of Toronto, and there will be continued contributions of bacteria, nutrients and sediments into the watercourses from the "905" municipalities north of the City of Toronto.
Over the next 25 years, implementation of the WWFMMP will improve waterfront aquatic habitats by reducing inputs of nutrients, sediments and chemical pollutants to the watercourses and Lake Ontario. It will also improve habitat conditions in the rivers and creeks, with benefits to aquatic species that migrate upstream from the Lake and estuaries
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Invasive Species
Invasive species have also been responsible for major alterations in aquatic communities. Since the 1800s, more than 140 exotic aquatic organisms of all types — including plants, fish, algae and mollusks — have become established in the Great Lakes. One of the most dramatic recent invasions has been the zebra mussel, which colonizes rocky substrates and other hard surfaces. Zebra mussels are highly efficient filter feeders, removing substantial amounts of phytoplankton and zooplankton from the food chain. They have also caused significant improvements in water clarity, which in turn is increasing the diversity and productivity of aquatic plants in the nearshore zone.
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Lakefilling
During the industrial period from 1900-1960, extensive lakefilling transformed the 826 hectare Ashbridge's Bay wetland complex, most of the central waterfront south of Front Street, portions of the Toronto Islands including the airport, the Leslie Street Spit, Ontario Place and the Western Beaches, as seen below.
In the 1970's, the Metro Toronto and Region Conservation Authority began to develop a series of lakefill parks along the waterfront (Colonel Sam Smith, Humber Bay, Ashbridge's Bay, and Bluffers Parks) to provide recreation opportunities for a rapidly increasing urban population.
Industrial Period Alterations to the Toronto Bay, 1900 to
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Dredging Activities
The Toronto Port Authority undertakes dredging in the Keating Channel, Inner Harbour, East Gap, Western Channel, Coatsworth Cut and Ashbridges Bay
Each year, 35,000 to 40,000 cubic metres of sediment settle in the Keating Channel. The material originates from run-off and erosion upstream in the Don River. Annual dredging is undertaken in the channel for flood protection and maintenance of navigable water. The channel is dredged to a depth of 5.8 metres below chart datum and the dredged material is transported by tug and barge to the Toronto Port Authority's Confined Disposal Facility (CDF) within the Leslie Street Endikement. The project is subject to ongoing environmental monitoring by the Port and Conservation Authorities. The dredging operation is jointly funded by the City of Toronto, the Toronto and Region Conservation Authority (TRCA) and the Toronto Port Authority.
Although the majority of sediment from the Don watershed is captured in the Keating Channel, aerial photographs plainly show a plume of sediment that makes its way further, into the Inner Harbour. When needed, small quantities of material are dredged at berths to maintain the required depth for shipping. Quantities in the order of 3,000 cubic metres are dredged every three to five years. Similar to the Keating Channel dredgate, the material is transported to the Toronto Port Authority's CDF. In general, Berth Nos. 275, 352 and 353 are dredged to 8.2 metres below chart datum while Berth Nos. 243 and 245 are dredged to 5.8 metres below chart datum.
The East Gap represents a portion of the main shipping channel into Toronto Harbour. Prior to the construction of the Leslie Street Spit, regular dredging of the Gap was required to maintain the navigation depth of 8.2 metres below chart datum. Some sediment continues to intrude into the Gap from western littoral drift and erosion off the Centre Islands. The quantity of this sediment is in the order of 3,500 cubic metres per year. The Toronto Port Authority is currently undertaking a five-year program to remove approximately 60,000 cubic metres of material from the Gap. This material consists of clean sand suitable for open water disposal in accordance with MOE guidelines. The Port Authority has worked with TRCA to use the clean material in Embayment "A" of Tommy Thompson Park to improve aquatic habitat conditions and develop an emergent vegetation wetland area.
Similar to the East Gap, erosion of the shoreline of the Toronto Islands results in transportation of material into the Western Channel and restricts navigation. Preliminary work is currently underway to assess possible alternatives for the disposal of the dredged material. An environmental assessment will be undertaken and dredging will probably commence within the next two years. The current design depth of the channel is 8.2 metres below chart datum, but may be reduced as a result of the environmental assessment.
Maintenance dredging is required in the Coatsworth Cut channel in Ashbridge's Bay every two or three years. The design depth of the channel is 1.8 metres below chart datum. The Toronto Port Authority has permitted this dredge material to be transported and disposed in the Toronto Port Authority's Confined Disposal Facility. This dredging is funded by the City and coordinated by TRCA.
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Shoreline Regeneration Initiatives
Cultural modifications of the shoreline changed dramatically with the advent of the 1967 Waterfront Plan developed by Metro Toronto. Lakefilling activities were directed away form creating port and industrial lands and focussed on creating a series of regional waterfront recreational parks. The parks provided waterfront access, local greenspace, boating facilities, and — most important to this strategy — aquatic habitats. Following is a summary of the key projects.
Sam Smith Waterfront Park incorporates many successful habitat creation projects, including wetlands, coastal meadows, shoals and reefs.
 Humber Bay Park Park is the site of a range of intensive habitat restoration works. They include a Ministry of Natural Resources habitat project that placed extensive amounts of woody debris in a sheltered embayment. Test scale wetlands were established in the estuary of Mimico Creek in 1995 and additional wetlands were created in association with the pedestrian bridge over the Creek. The estuary now provides an excellent opportunity to recreate a coastal wetland estuary complex. As part of the development of the Humber Bay Shores area, habitat islands, beaches and shoals have been strategically built along the east side of Humber Bay Park, including one of the largest wetland creation projects to date.
 The Toronto Bay area was the focus of a study by the Toronto Bay Initiative (A Living Place: opportunities for habitat regeneration in Toronto Bay) that outlines many habitat opportunitiesvi. The wetland project and pike spawning habitat at Spadina Quay is an excellent example of created habitats within the harbour and is a useful design template for larger initiatives. The restoration of the lower Don River and the wetland at the mouth of the Don River is one of the largest proposed restoration schemes for the Toronto Waterfront.
Within the Toronto Islands at the trout pond, a large wetland complex was enhanced and reconnected to the lagoons. This lacustrine marsh provides critical habitat functions for the fish and wildlife community of the islands. Works undertaken in the mid 1990's on the islands focussed on repairing vertical seawalls with a variety of shoals and riparian improvements. Of particular interest is the wetland shoreline that was created at the Queens City Yacht Club that provides vegetated shorelines and improved public access.
 The potential for Tommy Thompson Park to act as an aquatic habitat catalyst for the waterfront is based on the habitat opportunities in the 160 hectares of lagoons and bays associated with the park. The Cell One wetland capping project is the single largest wetland gain to date on the waterfront. Additional wetland creation projects in the Park include Triangle Pond, Embayment A, and Embayment C.
Ashbridge's Bay and Bluffer's Parks are the location of two of the very first shoal and reef features within a boat basin on Toronto's waterfront. Both parks have tremendous potential for additional habitats works.
 East of Ashbridge's Bay, the open coast shoreline is characterized by groynes and headland features. Overall these structures function well as aquatic habitat with the best example being the recent headland structure west of the RC Harris Water Filtration Plant. East of Bluffer's Park, the Sylvan Avenue project is an outstanding example of integrating aquatic habitats into the form and function of an erosion control project. The Port Union Road shoreline improvement project is another example of the integration of aquatic habitats into a shoreline management structure.
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i Whillans, T. Waterfront Ecosystems: Restoring is Remembering. In Roots, B.I, Chant, D.A. and Heidenreich, C.E. 1999. Special Places: the changing ecosystems of the Toronto Region. Royal Canadian Institute.
ii Etobicoke and Mimico Creek Watersheds Task Force. 2002. Greening our Watersheds: Revitalization Strategies for Etobicoke and Mimico Creeks. Toronto and Region Conservation Authority.
iii Whillans, T. Waterfront Ecosystems: Restoring is Remembering. In Roots, B.I, Chant, D.A. and Heidenreich, C.E. 1999. Special Places: the changing ecosystems of the Toronto Region. Royal Canadian Institute.
iv Toronto and Region Remedial Action Plan. 2001. Clean Waters, Healthy Habitats. Progress Report 2001. Waterfront Regeneration Trust.
vCity of Toronto. 2003. Wet Weather Flow Management Master Plan. www.city.toronto.on.ca/wes/techservices/involved/wws/wwfmmp
viKidd, J. 1998. A Living Place: Opportunities for Habitat Regeneration in Toronto Bay. Toronto Bay Initiative.
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