The River Forth is a major river in central Scotland, 47 km (29 miles) long, which drains into the North Sea on the east coast of the country. Its drainage basin covers much of Stirlingshire and Clackmannanshire in Scotland's Central Belt. The Gaelic name for the upper reach of the river, above Stirling, is Abhainn Dubh, meaning "black river". The name for the river below the tidal reach (just past where it is crossed by the M9 motorway at Stirling) is Uisge For.
The River's Course
The Forth rises in the Trossachs, a mountainous area 30 km (19 miles) west of Stirling. Ben Lomond's eastern slopes drain into the Duchray Water, which meets with Avondhu River coming from Loch Ard. The confluence of these two streams is the nominal start of the River Forth, roughly 33 metres (108 feet) above sea level.
From there it flows roughly eastward through Aberfoyle, joining with the Kelty Water about 5 km further downstream. It then flows into the flat expanse of the Carse of Stirling, including Flanders Moss. Just west of the M9, it is joined by the river Teith (which itself drains Loch Venachar, Loch Lubnaig, Loch Achray, Loch Katrine, and Loch Voil). The next tributary is the Allan Water, just east of the M9. From there the Forth meanders into the city of Stirling.
At Stirling the river widens and becomes tidal. This is the location of the last (seasonal) ford of the river. From Stirling, the Forth flows east, accepting the Bannock Burn from the south before passing the town of Fallin. It then passes into Clackmannanshire, meeting firstly Cambus (where it is joined by the river Devon), closely followed by Alloa (just after which it is met by the Black Devon). Upon reaching Airth (on the river’s south shore) and Kincardine (on its north shore), the river begins to widen and becomes the Firth of Forth. From then eastwards, ships ply the waters. In earlier times the river was navigable as far as Stirling, with several ports, including Clackmannan Pow, Alloa Harbour and Stirling Harbour. Nowadays navigation for ships is restricted west of Kincardine Bridge.
River Crossings
Upstream from Stirling, the river is rather narrow and can be crossed in numerous places. (Crossing used to be more difficult before the installation of modern drainage works, because the ground was often treacherously marshy near the riverbank.) However, after its confluence with the Teith and Allan, the river becomes wide enough that a substantial bridge is required. At Stirling, there has been a bridge over the river since at least the 13th century, and it was the easternmost road crossing until 1936, when another road crossing was opened at Kincardine. The Clackmannanshire Bridge, just upstream of the Kincardine Bridge, opened on 19 November 2008. A railway bridge, the Alloa Swing Bridge, previously connected Alloa on the northern shore with Throsk (and beyond) on the southern shore. It opened in 1885 and was closed and mostly demolished in 1970. Only the metal piers remain.
Much further downstream, joining North Queensferry and South Queensferry, is another railway bridge, the famous Forth Bridge, which opened in 1890, and the Forth Road Bridge, which opened in 1964. To the west of the Forth Road Bridge is Queensferry Crossing, which opened in 2017.
Geologically, the Firth of Forth is a fjord, formed by the Forth Glacier in the last glacial period. The drainage basin for the Firth of Forth covers a wide geographic area including places as far from the shore as Ben Lomond, Cumbernauld, Harthill, Penicuik and the edges of Gleneagles Golf Course in Perthshire.
From 1964 to 1982, a tunnel existed under the Firth of Forth, dug by coal miners to link the Kinneil colliery on the south side of the Forth with the Valleyfield colliery on the north side. The shafts leading into the tunnel were filled and capped with concrete when the tunnel was closed, and it is believed to have filled with water or collapsed in places.
The inner firth, located between the Kincardine and Forth bridges, has lost about half of its former intertidal area as a result of land reclamation, partly for agriculture, but mainly for industry and the large ash lagoons built to deposit spoil from the coal fired Longannet Power Station near Kincardine. Historic villages line the Fife shoreline; Limekilns, Charlestown and Culross, established in the 6th century, where Saint Kentigern was born.
The firth is important for nature conservation and is a Site of Special Scientific Interest. The Firth of Forth Islands SPA (Special Protection Area) is home to more than 90,000 breeding seabirds every year. There is a bird observatory on the Isle of May. A series of sand and gravel banks in the approaches to the firth have since 2014 been designated as a Nature Conservation Marine Protected Area under the name Firth of Forth Banks Complex.
Islands
Two islands (known as “inches”) lie in the meandering estuarine waters downstream from Stirling: Tullibody Inch, near Cambus, and Alloa Inch, near Alloa. Both islands are fairly small, and are once again uninhabited, having now become nature reserves. There are a few more islands further east in the firth of Forth, none of which are permanently inhabited These are: -
Bass Rock
Craigleith
Cramond
Eyebroughy
Fidra
Inchcolm
Inchgarvie
Inchkeith
Inchmickery
Lamb
Isle of May