Mardyke (river)

Mardyke
Mar Dyke
River
The Mardyke near Purfleet
Country	England
Counties	Essex
Towns	Thurrock
Source	Holden's Wood
- location	Between Great Warley and Little Warley
- coordinates	51°35′52.13″N 0°17′36.3″E / 51.5978139°N 0.293417°E / 51.5978139; 0.293417
Mouth	River Thames
- location	Purfleet
- coordinates	51°29′9.29″N 0°13′41.14″E / 51.4859139°N 0.2280944°E / 51.4859139; 0.2280944Coordinates: 51°29′9.29″N 0°13′41.14″E / 51.4859139°N 0.2280944°E / 51.4859139; 0.2280944
Length	18 km (11 mi)
Basin	90.7 km2 (35 sq mi)
Discharge	for Stifford
- average	0.48 m3/s (17 cu ft/s)

The Mardyke (sometimes, but less frequently, Mar Dyke, occasionally Mardike) is a small river, mainly in Thurrock, that flows into the River Thames at Purfleet, close to the Queen Elizabeth II Bridge. In part, it forms the boundary between the Essex hundreds of Barstable and Chafford. The river gives its name to the Mardyke Valley—a project aimed at increasing appreciation and usage of recreational land around the Mardyke.

The main source of the Mardyke is in Holden's Wood between Great Warley and Little Warley. It flows roughly 11 miles (18 km) from the source to the Tideway of the Thames at Purfleet, close to the Queen Elizabeth II Bridge. There are two tributaries flowing south from Thorndon Country Park, in the grounds of Thorndon Hall. One of these flows south from Old Hall Pond. The pond has a sluice gate that could be opened to allow the water to flow over artificial waterfall – the sort of water feature popular with landscape gardeners such as Lancelot "Capability" Brown who landscaped the grounds of Thorndon Hall in the 18th century, although the pond itself dates from the 13th century. Another tributary flows west from Dunton Plotlands section of the Langdon Nature Reserve in Langdon Hills and another flows east from Upminster.

The name means "boundary ditch". It is mentioned in an Anglo-Saxon charter dated 1062 (S 1036) as part of the boundary for Upminster, although this charter is probably a post-conquest forgery. It has also been called "the Flete" (flete is derived from flēot, an Old English word for "small estuary") and more simply "the brook". One of the Mardyke's tributaries flows from Childerditch. This name appears as "celta" in a 7th-century charter (S 1246). Celta may be the pre-Saxon name for the ditch which flows into the Mardyke and may also be an early name for the Mardyke itself. For most of its course, the river acts as a parish boundary and in part, the river forms the boundary between the Essex hundreds of Barstable and Chafford.