Netham lock is the point at Netham in Bristol

Bristol

Bristol is a city, unitary authority area and ceremonial county in South West England, with an estimated population of 433,100 for the unitary authority in 2009, and a surrounding Larger Urban Zone with an estimated 1,070,000 residents in 2007...

 at which boats from the River Avon

River Avon, Bristol

The River Avon is an English river in the south west of the country. To distinguish it from a number of other River Avons in Britain, this river is often also known as the Lower Avon or Bristol Avon...

, acting as part of the Kennet and Avon Canal

Kennet and Avon Canal

The Kennet and Avon Canal is a waterway in southern England with an overall length of , made up of two lengths of navigable river linked by a canal. The name is commonly used to refer to the entire length of the navigation rather than solely to the central canal section...

, gain access to Bristol's Floating Harbour.

Construction started in 1804 to build the tidal New Cut

New Cut (Bristol)

The New Cut is an artificial waterway which was constructed between 1804 and 1809 to divert the tidal river Avon through south and east Bristol, England. This was part of the process of constructing Bristol's Floating Harbour, under the supervision of engineer William Jessop...

 and divert the River Avon

River Avon, Bristol

The River Avon is an English river in the south west of the country. To distinguish it from a number of other River Avons in Britain, this river is often also known as the Lower Avon or Bristol Avon...

 along the Feeder Canal to the harbour; a system designed and built by William Jessop

William Jessop

William Jessop was an English civil engineer, best known for his work on canals, harbours and early railways in the late 18th and early 19th centuries.-Early life:...

 and later improved by Isambard Kingdom Brunel

Isambard Kingdom Brunel

Isambard Kingdom Brunel, FRS , was a British civil engineer who built bridges and dockyards including the construction of the first major British railway, the Great Western Railway; a series of steamships, including the first propeller-driven transatlantic steamship; and numerous important bridges...

.

A weir

Weir

A weir is a small overflow dam used to alter the flow characteristics of a river or stream. In most cases weirs take the form of a barrier across the river that causes water to pool behind the structure , but allows water to flow over the top...

 carries the river into the New Cut and boats use the adjacent lock

Lock (water transport)

A lock is a device for raising and lowering boats between stretches of water of different levels on river and canal waterways. The distinguishing feature of a lock is a fixed chamber in which the water level can be varied; whereas in a caisson lock, a boat lift, or on a canal inclined plane, it is...

. High tide

Tide

Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....

s often pass over the weir, and the river is effectively tidal to the next lock upstream at Hanham

Hanham Lock

Hanham Lock is situated on the River Avon, at the village of Hanham near Bristol, England.Hanham Lock is the first lock east of Netham where boats leave the Bristol Floating Harbour. A weir carries the river and boats use the adjacent lock. It is numbered as 1 and is officially the first on the...

. Some spring tides can also pass over the weir at Hanham, making the river tidal as far as Keynsham lock

Keynsham Lock

Keynsham Lock is situated on the River Avon at Keynsham, England.The lock opened in 1727.Just above the lock are some visitor moorings and a pub, on an island between the lock and the weir. The weir side of the island is also the mouth of the River Chew....

.

Access to the harbour is only possible during the day when the lock keeper will open the gates unless the water level in the river between Netham and Hanham is above or below the level of the harbour.

The maximum dimensions of a vessel which can pass through Netham Lock are:

• Length: 24.4 metres (80.1 ft)
• Beam: 5.4 metres (17.7 ft)
• Draught: 1.9 metres (6.2 ft)
• Headroom: 3.1 metres (10.2 ft)

The lock-keeper's cottage, built in the early nineteenth century, is a grade II listed building and has a plaque listing it as Bristol Docks building number 1. The floral displays around the cottage and on the banking have attracted praise.

Netham Lock and the weir form part of Bristol's flood defence mechanisms and it was announced in December 2008 that they would be upgraded as part of the £11 million City Docks Capital Project.

See also

• Locks on the Kennet and Avon Canal
  Locks on the Kennet and Avon Canal
  The Kennet and Avon Canal is a canal in southern England. The name may refer to either the route of the original Kennet and Avon Canal Company, which linked the River Kennet at Newbury to the River Avon at Bath, or to the entire navigation between the River Thames at Reading and the Floating...