User:Atrian/Don River

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Don River (Ne cheng qua kekonk)
The river as it runs beneath the Bloor Viaduct
Country	Canada
State	Ontario
Major cities	Toronto, Markham, Vaughan, Richmond Hill
Length	38 km (24 mi)
Watershed	360 km² (139 sq mi)
Discharge at	Keating Channel in the Toronto Harbour
- average	4 m³/s (141 cu ft/s)
Source	Oak Ridges Moraine
- coordinates	43°59′20″N 79°23′57″W / 43.98889, -79.39917
Mouth	Keating Channel
- coordinates	43°39′4″N 79°20′51″W / 43.65111, -79.3475
- elevation	75 m (246 ft)
Major tributaries
- left	Castle Frank Brook, Taylor-Massey Creek
- right	German Mills Creek

This article is about the river in Toronto, Canada. For other rivers with the same name, see Don River (disambiguation).

The Don River is one of two rivers bounding the original settled area of Toronto, Canada along the shore of Lake Ontario, the other being the Humber River to the west. The Don is formed from two rivers, the East and West Branches, that meet about 7 km north of Lake Ontario while flowing southward into the lake. The area below the confluence is known as the lower Don, and the areas above as the upper Don. The Don is also joined at the confluence by a third major branch, Taylor-Massey Creek. The Toronto and Region Conservation Authority (TRCA) is responsible for managing the river and its surrounding watershed.

[edit] Geography

[edit] Geology

The Don Valley is notable because of its deep wide valley in the lower reaches. At the Bloor Street Viaduct, the valley is about 400 m wide while the river is only about 15 m wide.^[1] This is due to its glacial origins. The Don River and its deep valley were formed about 12,000 years ago at the end of the Wisconsinan Glaciation. During that glaciation which lasted for 35,000 years, all of Ontario was covered in ice. As the climate warmed the glaciers began to melt. As the ice front retreated in southern Ontario, several rivers were formed that drained into Lake Iroquois, a glacier lake which was the precursor to Lake Ontario. The Don River is now small in comparison to the deep and wide valley that resulted from its glacial origin. The Don River is now classified as an underfit river.

The landscape at that time was loose glacial till so the large amounts of glacier melt water eroded deep valleys over thousands of years. As time progressed, isostatic uplift caused the earth's plate to rise and tilt. This caused Lake Iroquois to drain towards the south. A remnant of its shoreline can be seen on the north side of Davenport Road in Toronto. In the Don Valley, the old shoreline is evident just north of Eglinton Avenue.^[2] Today the source of the Don River is the Oak Ridges Moraine, another legacy of the Wisconsin glaciation.

The location of the old shoreline is important when considering soils in the Don watershed. Soils north of the old shoreline are mostly luvisolic Halton Till while south of the shoreline they are still sandy glaciolacustrine deposits.

The Don Valley contains one of the most interesting locations for studying the regional geological history. The Don Valley Brick Works was an old brick making factory with a quarry where they extracted shale. At the rear wall, local geologists discovered a record of the past three glaciations. There are nine distinct layers visible dating back 120,000 years.^[3]

[edit] Hydrology

Due to the urbanized nature of the watershed, the Don River experiences low base flows interspersed with high volume floods. The water level can rise very quickly following a moderate to heavy rainfall, up to 1-2 metres inside of three hours. The average base flow for the Don River is about 4 m³/s.^[4] Peak flows occur in late February and late September which corresponds to seasonal variation in the Toronto region. Maximum flows, based on a Hurricane Hazel style flood have been estimated at nearly 1700 m³/s.^[5] On August 19, 2005, an unusually strong summer storm caused short term flooding in the Don Valley. Peak flow rates for that event were measured at 55.3 m³/s. Since high flow rates occur during storm events, the resulting floods tend to scour the bottom of the river which reduces fish habitat. In addition, the flood waters carry a large amount of sediment washed into the river from surrounding tablelands. The sediment collects in the Keating Channel just past the mouth of the river. The TRCA which is responsible for the dredging estimates that the amount of sediment dredged is 35,000 m³/year weighing nearly 60,000 tonnes.^[6]

[edit] Physical description

The east branch of the Don, also called the Little Don River, rises at the south edge of the Oak Ridges Moraine just to the west of Yonge Street, flowing south-eastward through ravine forests in Richmond Hill, Thornhill, east of Willowdale and Don Mills. A second branch of the eastern Don, known as German Mills Creek, parallels the main eastern branch and joins it at Steeles Avenue, the northern boundary of Toronto. South of Lawrence Avenue the river passes through the Charles Sauriol Conservation Reserve. This area is mostly undeveloped parkland. The reserve occupies the valley south to the forks of the Don. It was at one time home of a Maple sugar shack and tapline, which was visited yearly by students from across East York. Charles Sauriol was a historic protector of the Don.

The western branch starts near Maple, Ontario, flowing south-east through the suburban industrial belt of Concord (Vaughan), and the G. Ross Lord Reservoir. It crosses Yonge Street as it flows through Hoggs Hollow, past York University's Glendon ("valley of the Don") campus, and then flows on to Leaside before joining the eastern half.

Downstream from the forks, the river flows through a wooded area known as Crothers' Woods which is designated as an Environmentally Sensitive Area due to the high quality beech-maple forest that grows on the ravine slopes. South of Pottery Road it enters a more degraded section and ends up in a straightened section that includes cement and steel dock wall, a remnant from an earlier industrial era. The river flows unceremoniously into the Keating Channel at Lake Shore Blvd. East which is at the north east corner of the Toronto Harbour.

The western section of Taylor-Massey Creek and the southern portion of the western branch are surrounded by parkland (see also: Toronto ravine system). In more recent years the retreat of the industrial plants and rail infrastructure has freed up room which is now being turned into bicycling trails, which now extend from the shore of Lake Ontario northward in several directions to provide some 30km of off-road paved trails. While Toronto is fairly flat in general, local cyclists have developed a number of technically challenging singletrack trails throughout the area, following the main trails.

[edit] History

Humans first arrived in the Don approximately 12,500 years BP most likely as nomadic hunters.^[7] While there is little archaeological evidence in the Don valley itself, regional finds in the Great Lakes St. Lawrence area have revealed that permanent settlements started to occur about 6000 BP.^[8] The most significant recorded find is known as the Withrow Site. It was discovered in 1886 during road building just east of Riverdale Park. It contained human remains and other artifacts dating back to about 5000 years BP.^[7]

It is unclear whether the Don River had an native Canadian name. In 1788, Alexander Aitkin, an English surveyor who worked in southern Ontario, referred to the Don River as Ne cheng qua kekonk.^[9]. Elizabeth Simcoe, wife of Lieutenant Governor John Graves Simcoe, reported in her diary that another named used was Wonscotanach.^[10] This is an Anishnaabe phrase meaning black burnt grounds which could refer to an earlier forest fire. The Don River was named by J.G. Simcoe because the wide valley reminded him of the River Don in Yorkshire.

After the founding of York in 1793, several mills were constructed along the lower Don. One of the first was at Todmorden Mills. These mills initially turned out lumber, flour and paper products. By the 1850s, the Lower Don was becoming an industrial setting. Petroleum storage facilities, poultry and pork processing plants were constructed along the banks of the Don. In 1879, the Don Valley Brick Works opened.^[11] Polluted effluent from these factories and the growing city nearby was turning the Don and its marshy mouth into a polluted hazard.

In the 1880s the lower part of the Don south of the former Winchester St. bridge was straightened (east of the original mouth) and placed in a channel to create additional harbour space and industrial dock space for boats. Known as Don Improvement Project, the straightened river was also supposed to divert the polluted waters into the Ashbridges Bay marsh. This proved unsuccessful so the mouth was turned 90 degrees west where it empties into the inner harbour. This short extension of the harbour is known as the Keating Channel. The channel north of Lake Shore Blvd. East ceased being navigable when the Gardiner Expressway was constructed in the 1950s. Boats may still enter the Keating Channel by going underneath a lift bridge at Cherry St.

During the early part of the 20th century the river and the valley continued to be neglected. 31 separate sewage treatment facilities were built along the river.^[12] Over 20 places in the valley and adjacent ravines were used as landfills for garbage and industrial refuse.^[13] In 1917, the Don Destructor was built beside the Don just north of Dundas Ave. East. It was used as a garbage incinerator for 52 years burning about 50,000 tonnes per year.^[14]

After World War II, rapid urban expansion occurred in the northern reaches of the watershed. In 1954, Hurricane Hazel struck the Toronto area. Intensive flooding affected the lower reaches. Flood waters affected downtown Toronto as far east as Leslie Street and as far west as Bay Street. While no loss of life occurred in the Don Watershed the result of this storm was that the TRCA was given a mandate to construct flood control features as well as acquire property in the Don Valley as well as along its major tributaries. Large tracts of industrial land adjacent to the river were added to the regulatory floodplain. This meant that the TRCA had a veto on any developments that were not floodproofed.

In the early 1960s, the Don Valley Parkway was constructed through the Lower Don to serve the growing commuter traffic. The increasing development reduced the natural areas of the watershed. This impacted the Don with increased pollution, heavy flooding, and turbid sediment laden waters. The combined result meant that by the 1960s the river was a neglected, polluted mess. In 1969, Pollution Probe held a much celebrated “Funeral for the Don” to highlight the plight of the river.^[11]

Efforts to restore the Don gathered steam in 1989 with a public forum at the Ontario Science Centre which was attended by about 400 people. The result was the formation of the Task Force to Bring Back the Don, a citizen’s advisory body to Toronto City Council. Their mandate and vision was to make the Don “clean, green, and accessible”. Since then they have hosted garbage cleanups, tree plantings, and help to create or restore eight wetlands in the lower reaches of the valley, including Chester Springs Marsh, a 3 ha site south of the Bloor Viaduct.^[15] Other groups also became active including Friends of the Don East. The TRCA created the Don Watershed Regeneration Council to coordinate restoration efforts throughout the watershed.

In 1991 Bring Back the Don released a document called “Bringing Back the Don” which laid out plans for restoration, including a renaturalized mouth of the Don. In 1998 a plan to revive Toronto’s waterfront was initiated. One of the four projects mentioned was a natural mouth for the Don River. In 2001 an environmental assessment was started to look into a natural mouth of the Don. The project was also coupled with a plan to handle a major flood modeled on the expected output from a Hurricane Hazel size storm. In 2007, the Toronto Waterfront Development Corporation (now WaterfrontToronto) held a design competition that looked at four different configurations for the mouth of the Don. The winning bid was made by Michael Van Valkenburgh Associates.^[16] The environmental assessment is expected to be complete in 2000 and construction is scheduled to begin in 2010.^[17]

[edit] Current issues

[edit] Wet weather flow

One of the biggest problems of the Don is wet weather flow (rainfall and snowmelt). In the older part of Toronto, most of the sewers were built as combined sewer overflows. These sewers carry both sanitary effluent and storm runoff. Several of them empty directly into the river. During regular flows the effluent is directed to sewage treatment plants. However when it rains, the storm runoff mixes with the sanitary sewage and this flows directly into the river. This causes pollution levels to rise especially such dangerous pollutants such as e.coli.

[edit] Infrastructure

The Lower reach of the Don Valley is crowded with transportation and power corridors. At the Gerrard St. bridge there is the Don Valley Parkway, the Bayview Extension, two railway lines, one hydroelectric power line, two pipelines and one pedestrian/bicycle path. The river itself is encased concrete and steel dockwall which leaves little room for natural function.

Castlefrank Brook, a tributary of the Don, has been completely buried so that roads and subways could be constructed.

Sewer pipes have been placed in various places. These cause problems of disturbance not only during construction but also in the future when they are in need of repair.

Even today, future infrastructure is still being contemplated. In the Wet Weather Flow Management Master Plan, there is a plan to build a stormwater containment cistern underneath the Don Valley Parkway. Similar to reservoirs built underneath Toronto beaches, it would be designed to capture output from CSOs before it enters the river.

[edit] Invasive species

Before European colonization, the Don Valley was mostly covered with a beech-maple forest which was common in Southern Ontario. Since then, most of it has been removed for agricultural and urban uses

[edit] See also

Wikimedia Commons has media related to:

Don Valley

• List of Ontario rivers

[edit] References

[edit] External links

• Don Watcher weblog
• Don Watershed Regeneration (by Mark Wilson)
• Environment Canada (Toronto Remedial Action Plan) Great Lakes Portrait: Bringing back the Don River
• Friends of the Don East
• Lost Rivers Walks and Local History
• Map of and links to the buried waterways of the Lower Don
• Task Force to Bring back the Don
• Todmorden Mills Wildflower Preserve
• TRCA’s page on the Don Watershed

[edit] Pictures

Foot of the Don, just before it exits into the shipping channel. The overpass in the foreground is the foot of the Don Valley Parkway as it exits onto the elevated Gardiner Expressway seen in the background. Note the algae covering most of the river.