User:Alaney2k/Bridges of the Don Valley

The Don River valley of Toronto, Ontario is an ancient natural glacial spillway. Because of the high discharges during the melting of ice sheets, a large amount of sedimentary land was displaced, causing a wide valley with steep sides. European settlers found the valley to be an ideal location to set up mills and local industry. Alongside the valley, the city of Toronto grew and numerous streets were needed and several crossed the Don River. Today there are several dozen bridges over the Don River; several are notable engineering achievements; several are abandoned bridges from settler times or abandoned roadways cut off during the construction of the Don Valley Parkway and Gardiner Expressway.

The bridges of the Don River can be classed into three separate classes:
 * railway bridges (serving the Canadian National Railway (CNR) and Canadian Pacific Railway (CPR)
 * roadway bridges
 * pedestrian bridges

Railways entered the Don River valley starting in the 1870s. The CPR entered the valley in the 1880s.

The bridges of the Don River valley are organized from south (location of the mouth) to north. At Don Mills Road, the Don forks into the West Don River, the East Don River and Massey Creek.

Lower Don River bridges
The Lower Don valley extends from Lake Ontario north to the 'Forks of the Don' around the interchange of Don Mills Road and the Don Valley Parkway. There are several large bridges of the Lower Don that extend from one side of the valley to the other, including the Leaside Bridge and the Prince Edward Viaduct, but most are at the level of the floodplain.

The Lower Don is dominated by the Don Valley Parkway freeway, inhabiting the entire eastern bank except for some flats around Riverdale Park. The Parkway passes under several bridges of the valley, making overpasses only over the Bayview/Bloor off-ramp, Pottery Road and Beechwood Avenue.

West Don valley
North-east of the Leaside bridge, the Don River forks into east and west forks. The West Don River flows from the north-west, originating north of Toronto, north-west of Dufferin Avenue. It continues in a south-east direction in a wide deep valley with from north of Sheppard to south of Yonge and York Mills Road, then to east of Bayview Avenue and Lawrence Avenue. The valley narrows, reaching the Forks of the Don in a tall, narrow ravine.

There are several large bridges built to cross the valley, from the Highway 401 overpass, the bridges at Hogg's Hollow at Yonge and York Mills Road and at Bayview, just north of Lawrence. Most of the West Don valley floodplain has never been urbanized due to the steep slopes making the floodplain difficult to reach, though it has been lumbered and farmed in some locations.

East Don valley
North-east of the Leaside bridge, the Don River forks into east and west forks. The Taylor Massey Creek flows into the East Don a short distance from the fork of the east and west Don branches. The East Don fork continues in a north-easterly direction. Near Steeles Avenue, the German Mills Creek feeds into the East Don.

The East Don is impacted by the Don Valley Parkway, which follows the East Don just east of the Forks, then crosses the East Don at Lawrence Avenue. Both the CNR and CPR rail lines cross the East Don valley, with the CNR tracks following the East Don north of Toronto.