River Mole

River Mole. The River Mole is a significant watercourse in southern England, flowing primarily through the counties of Surrey and a portion of West Sussex. It rises near Horsham and travels northwards for approximately 50 miles before joining the River Thames at Hampton Court Palace. The river is notable for its distinctive behaviour of disappearing underground in sections of its upper course, a phenomenon known as 'moles', which gives the river its name. Its catchment area supports diverse settlements and habitats, playing a key role in the regional landscape.

Course

The river originates from several springs to the south of Horsham in the Weald. It flows initially northwards, passing near the village of Rusper and through the town of Crawley. Continuing north, it enters the Surrey Hills Area of Outstanding Natural Beauty, flowing through the market town of Dorking where it passes through the famous Box Hill beauty spot. The course then turns northwest, skirting the edges of Leatherhead and Esher, before its final confluence with the River Thames on the reach above Teddington Lock at East Molesey. Major tributaries include the River Eden, which joins near Painshill Park, and the Pipp Brook which meets it near Westcott.

Hydrology

A defining hydrological feature is its tendency to sink into the underlying chalk and sandstone in the area between Dorking and Leatherhead, particularly in the Mickleham valley near the Swiss Cottage. These swallow holes, historically a hazard to milling, cause sections of the riverbed to run dry seasonally. The river is prone to significant flooding, with notable events impacting Dorking, Leatherhead, and East Molesey throughout history. Management of its flow is influenced by structures like the Ember Court weir and its interaction with the underlying Greensand Group geology, which affects groundwater recharge and discharge patterns.

History

The river is recorded in the Domesday Book as the *Emlyn* stream. Its fords were historically vital crossing points, influencing the location of settlements like Cobham. From the medieval period, the river's power supported numerous watermills, including those at Betchworth and Slyfield. The landscape around it was shaped by estates such as Norbury Park and Claremont Landscape Garden. The arrival of the London and Southampton Railway and later lines like the Epsom and Leatherhead Railway bridged the valley, with notable structures including the Mole Gap viaducts. During the Second World War, its valley was part of the GHQ Line, a defensive stop-line against invasion.

Ecology

The river and its riparian zones support a variety of habitats, from chalk streams to wet woodland. It is a designated site for several protected species, including the endangered European eel and the white-clawed crayfish. The river corridor through the Mole Gap is a Site of Special Scientific Interest noted for its geological exposures and invertebrate populations. Conservation efforts are undertaken by organizations like the Surrey Wildlife Trust and the Environment Agency, focusing on improving water quality and managing invasive non-native species such as Himalayan balsam. The floodplain meadows provide important habitats for birds and insects.

Cultural references

The river has inspired numerous artists and writers. It is famously mentioned in John Milton's pastoral poem *Lycidas* and is depicted in landscapes by the painter J. M. W. Turner. The novelist Daniel Defoe commented on its disappearing act in his *Tour*. In the 20th century, it featured in the works of local author E. M. Forster. The river's name is echoed in local landmarks like the Mole Valley district and is celebrated in the annual River Mole environmental activities. Its scenic beauty around Box Hill is immortalized in Jane Austen's novel *Emma*. Category:Rivers of Surrey Category:Rivers of West Sussex Category:Tributaries of the River Thames