|- location||Confluence of Hunsworth Beck and Nann Hall Beck in Cleckheaton|
|- elevation||81 metres (266 ft)|
|River Calder at Dewsbury|
|42 metres (138 ft)|
|Length||8 kilometres (5.0 mi)|
|Basin size||46.3 square kilometres (17.9 sq mi)|
The River Spen, known colloquially as Spen Beck, is a river in the county of West Yorkshire, England and is a tributary of the River Calder. It rises north of Cleckheaton, runs through Liversedge and flows into the River Calder, West Yorkshire south of Dewsbury at Ravensthorpe. The average rainfall for the river valley is between 600-1000mm per annum. Combined with the steep narrow river channel, this makes the Spen susceptible to regular flooding.
The river becomes the Spen at the confluence of Hunsworth Beck and Nann Hall Beck in Cleckheaton. It flows south past local Industrial premises parallel to a dismantled railway line before turning south east on the outskirts of Liversedge. It continues flowing in this direction through the heart of the Industrial centre of the town before returning southwards along the edge of Heckmondwike. On the outskirts of the village of Ravensthorpe it turns south east again before joining the River Calder.
The river is mainly an urban waterway and has suffered from sewage effluent and industrial waste, though levels of pollutants and mine water discharges have decreased since 1999. Heavy rain can cause pollutant levels to rise and the river suffers from tipping and urban litter.
There are several non-native species of plant found along the river including Giant Hogweed, Himalayan Balsam and Japanese knotweed. Bistort, wild garlic, nettles and dandelions are found in abundance in the meadows between the conurbations.
The disused railway line next to the riverbank is used as part of the Spen Valley Greenway (National Cycle Route 66) from Dewsbury to Oakenshaw near Bradford. The path is home to a collection of artworks, including A Flock of Swaledale Sheep, constructed from recycled industrial scrap by Sally Matthews, and Rotate by Trudi Entwistle which comprises 40 giant steel hoops set in a circle.
Ordnance Survey Open Data