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EspañolRIVER MOLE, SURREY
The 'River Mole' is a river in southern England, which rises in West Sussex near Gatwick Airport and flows north west through Surrey for 80 km (50 miles) to the River Thames at Hampton Court Palace. The river gives its name to the Surrey district of Mole Valley. At the Island Barn Reservoir near Molesey, the river splits into two distributaries: the northern (and smaller) branch continues as the River Mole and the southern branch is known as the River Ember. The two rivers flow either side of the reservoir, before flowing side by side in a north easterly direction towards the River Thames merging 400 metres before the confluence.
The drainage area of the River Mole is 512 km² and forms 5% of the River Thames catchment area above Teddington. Annually the catchment area receives 761 mm rain each year, the greatest average level of rainfall is 800 mm rain around Crawley. There is only one aquifer in the drainage basin at Fetcham, which means that the majority of the water in the river is from surface drainage, particularly from Gatwick Airport and the urban areas of Horley and Crawley and that the flow rate responds rapidly to rainfall.[1]
The River Mole is so named because in very dry summers the stretch between Dorking and Leatherhead can become completely dry, (most recently in 1976) and appears to have burrowed underground.
The underlying rock type in this part of Surrey is chalk and the water table lies permanently below the level of the riverbed. This allows water to drain out of the river through tiny swallow holes in the banks. (Water is unable to drain through the river bed, due to the clay silt deposits washed downstream from the Weald.) At Leatherhead, the river leaves the chalk and flows across impermeable London Clay. It is at this point that the water table rises sufficiently, enabling the water to flow back into the main river channel. In a survey in 1958, the geologist C.C. Fagg, identified twenty five swallow holes between Dorking and Mickleham.
[1]
At Burford Bridge, Box Hill near Dorking the average flow of the Mole is 63 million gallons a day. Further downstream at Leatherhead the discharge does not increase as expected but falls by 8 million gallons to 55 million gallons. [3] This effect is most noticeable in the summer when the water level is at its lowest, however the process occurs thoughout the year.
The North Downs Way crosses the river at Box Hill via seventeen hexagonal stepping stones, which are frequently submerged after heavy rainfall. The location is popular both with anglers and families, although swimming is strongly discouraged. The stones give their name to the pub in the nearby village of Westhumble.
There are three listed bridges in Leatherhead of which the 14 arch Shell Bridge, built in 1784 is the oldest. It links two small islands in the center of the river with each bank.
The earliest recorded watermill on the river was at Cobham, downstream of Leatherhead, which was noted in the Domesday Book of 1086. The present red brick mill dates from the 1822 and was in use until 1928. In 1953 the main part of the mill was demolished by Surrey County Council to allieviate traffic congestion on Mill Road. The remaining building was restored to full working order by the Cobham Mill Preservation Trust, and is now open to the public from 2pm to 5pm on the second Sunday of each month (between April and October).
The 'Gatwick Stream' is dominated by coarse fish such as brown trout, brook lamprey, and eel. In 2003 the River Mole at 'Meath Green' was enhanced to create a gravel spawning area to encourage chub and dace in addition to roach. In the 'Mole Gap' between Dorking and Leatherhead the river supports populations of chub, dace, barbel, brown trout. Both barbel and brown trout are extremely sensitive to water quality and pollution. Below 'Leatherhead' the river has historically supported larger predatory fish including chub, perch, pike, eels, however in recent years chub and eel numbers have begun to decline. North of 'Esher' the old river channel is dominated by floating pennywort, a highly invasive weed, which cut off all light to the river bed, reducing oxygen levels and resulting in a poor habitat for fish. The Ember flood relief channel has a diverse fish population, including chub, dace, roach, bleak, large pike and barbel.[1]
At the confluence of the Mole and the 'River Thames' it is possible to catch brown trout and flounder.[5]
The Mole Valley Corridor has been designated a local nature reserve.[6] The river's habitat has been enhanced as the river flows over a variety of different rock types: alluviums and gravel, chalk and clay. There are numerous different habitats: scrub, woodland, hedges, banks, and meadows as well as the water itself.
The River Mole originally flowed into the River Thames at the point where the present Hampton Court bridge now crosses the Thames (approximately 500 m upstream of the present confluence).
However, during the early 1930s, when Hampton Court Way and the bridge were built, the River Mole was redirected to flow into the River Ember and both rivers now enter the Thames in a single widened and straightened channel once occupied only by the River Ember. There have been further alterations to the courses of these two rivers in a major flood prevention scheme since serious flooding in the area in 1947 and 1968.[7]
Photograph of the River Ember Flood Relief Channel under construction in 1981. [8]
The order is from the mouth to the source:
★ Leigh Brook
★ Salfords Stream
★
★ Redhill Brook
★ Burstow Stream
★ Baldhorns Brook
★ Gatwick Stream
★
★ Stanford Brook
★ Holmwood Stream
★ Pipp Brook
★ The Rye
★ Bookham Brook
★ River Ember
★ Rivers of the United Kingdom
1. http://www.environment-agency.gov.uk/commondata/acrobat/mole_condoc_p1_1698235.pdf
2. http://www.environment-agency.gov.uk/commondata/acrobat/mole_condoc_p1_1698235.pdf
3. Box Hill information
4. http://www.environment-agency.gov.uk/commondata/acrobat/mole_condoc_p1_1698235.pdf
5. http://www.environmentagency.net/commondata/acrobat/river__tidal__562842.pdf
6. Mole Valley nature reserve
7. http://www.surreyproperty.com/east-molesey-history.html
8. http://www.geograph.org.uk/photo/4412
★ Environment agency
★ Groundwater quality
River Mole Catchment Area
The drainage area of the River Mole is 512 km² and forms 5% of the River Thames catchment area above Teddington. Annually the catchment area receives 761 mm rain each year, the greatest average level of rainfall is 800 mm rain around Crawley. There is only one aquifer in the drainage basin at Fetcham, which means that the majority of the water in the river is from surface drainage, particularly from Gatwick Airport and the urban areas of Horley and Crawley and that the flow rate responds rapidly to rainfall.[1]
Swallow Holes between Dorking and Leatherhead
The River Mole is so named because in very dry summers the stretch between Dorking and Leatherhead can become completely dry, (most recently in 1976) and appears to have burrowed underground.
The underlying rock type in this part of Surrey is chalk and the water table lies permanently below the level of the riverbed. This allows water to drain out of the river through tiny swallow holes in the banks. (Water is unable to drain through the river bed, due to the clay silt deposits washed downstream from the Weald.) At Leatherhead, the river leaves the chalk and flows across impermeable London Clay. It is at this point that the water table rises sufficiently, enabling the water to flow back into the main river channel. In a survey in 1958, the geologist C.C. Fagg, identified twenty five swallow holes between Dorking and Mickleham.
[1]
At Burford Bridge, Box Hill near Dorking the average flow of the Mole is 63 million gallons a day. Further downstream at Leatherhead the discharge does not increase as expected but falls by 8 million gallons to 55 million gallons. [3] This effect is most noticeable in the summer when the water level is at its lowest, however the process occurs thoughout the year.
Crossings of the River Mole
The North Downs Way crosses the river at Box Hill via seventeen hexagonal stepping stones, which are frequently submerged after heavy rainfall. The location is popular both with anglers and families, although swimming is strongly discouraged. The stones give their name to the pub in the nearby village of Westhumble.
There are three listed bridges in Leatherhead of which the 14 arch Shell Bridge, built in 1784 is the oldest. It links two small islands in the center of the river with each bank.
Watermills
The earliest recorded watermill on the river was at Cobham, downstream of Leatherhead, which was noted in the Domesday Book of 1086. The present red brick mill dates from the 1822 and was in use until 1928. In 1953 the main part of the mill was demolished by Surrey County Council to allieviate traffic congestion on Mill Road. The remaining building was restored to full working order by the Cobham Mill Preservation Trust, and is now open to the public from 2pm to 5pm on the second Sunday of each month (between April and October).
Fisheries
The 'Gatwick Stream' is dominated by coarse fish such as brown trout, brook lamprey, and eel. In 2003 the River Mole at 'Meath Green' was enhanced to create a gravel spawning area to encourage chub and dace in addition to roach. In the 'Mole Gap' between Dorking and Leatherhead the river supports populations of chub, dace, barbel, brown trout. Both barbel and brown trout are extremely sensitive to water quality and pollution. Below 'Leatherhead' the river has historically supported larger predatory fish including chub, perch, pike, eels, however in recent years chub and eel numbers have begun to decline. North of 'Esher' the old river channel is dominated by floating pennywort, a highly invasive weed, which cut off all light to the river bed, reducing oxygen levels and resulting in a poor habitat for fish. The Ember flood relief channel has a diverse fish population, including chub, dace, roach, bleak, large pike and barbel.[1]
At the confluence of the Mole and the 'River Thames' it is possible to catch brown trout and flounder.[5]
Mole Valley Corridor Local Nature Reserve
The Mole Valley Corridor has been designated a local nature reserve.[6] The river's habitat has been enhanced as the river flows over a variety of different rock types: alluviums and gravel, chalk and clay. There are numerous different habitats: scrub, woodland, hedges, banks, and meadows as well as the water itself.
River Ember Flood Relief Channel
The River Mole originally flowed into the River Thames at the point where the present Hampton Court bridge now crosses the Thames (approximately 500 m upstream of the present confluence).
However, during the early 1930s, when Hampton Court Way and the bridge were built, the River Mole was redirected to flow into the River Ember and both rivers now enter the Thames in a single widened and straightened channel once occupied only by the River Ember. There have been further alterations to the courses of these two rivers in a major flood prevention scheme since serious flooding in the area in 1947 and 1968.[7]
Photograph of the River Ember Flood Relief Channel under construction in 1981. [8]
Tributaries
The order is from the mouth to the source:
★ Leigh Brook
★ Salfords Stream
★
★ Redhill Brook
★ Burstow Stream
★ Baldhorns Brook
★ Gatwick Stream
★
★ Stanford Brook
★ Holmwood Stream
★ Pipp Brook
★ The Rye
★ Bookham Brook
Distributary
★ River Ember
See also
★ Rivers of the United Kingdom
References
1. http://www.environment-agency.gov.uk/commondata/acrobat/mole_condoc_p1_1698235.pdf
2. http://www.environment-agency.gov.uk/commondata/acrobat/mole_condoc_p1_1698235.pdf
3. Box Hill information
4. http://www.environment-agency.gov.uk/commondata/acrobat/mole_condoc_p1_1698235.pdf
5. http://www.environmentagency.net/commondata/acrobat/river__tidal__562842.pdf
6. Mole Valley nature reserve
7. http://www.surreyproperty.com/east-molesey-history.html
8. http://www.geograph.org.uk/photo/4412
External links
★ Environment agency
★ Groundwater quality
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