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Patterns, rates and possible causes of saltmarsh erosion in the Greater Thames area (UK)

Van der Wal, D. and Pye, K. (2004) Patterns, rates and possible causes of saltmarsh erosion in the Greater Thames area (UK). Geomorphology, 61, 373-391. ISSN 0169-555X.

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The estuary-dominated coast of the Greater Thames in England has experienced rapid lateral erosion and internal dissection of saltmarshes. This paper provides an overview of saltmarsh development in this area, and re-examines the role of environmental and human forcing factors. It draws on documentary evidence, including historical maps, survey data and time-series data of forcing factors. Lateral marsh retreat began in the 19th century in the Medway and Blackwater Estuaries, followed by other estuaries in the Greater Thames region at the beginning of the 20th century. The outer estuaries and the wider parts of the inner estuaries especially have experienced erosion. Erosion has been modest in wave-sheltered areas, e.g., the Colne and the inner Crouch. In the 1960s and, more widely, the 1970s, a phase of rapid erosion took place, with erosion rates of up to ca. 16 ha year-1 per site, notably along the open coast of Dengie and Foulness, and in the Blackwater and Thames Estuaries. At all sites, vertical sediment accretion was well able to keep up with sea level rise over the past century. Evidence indicates that there may have been several causes for the erosion of saltmarshes. These are notably land claim and embankment construction (increasing the tidal range and current velocities) and a continuous rise of, especially, high and extreme water levels. The latest episode of rapid erosion in the 1970s is largely attributed to changes in the wind/wave climate. For example, erosion at wave-exposed sites coincided with a peak in high magnitude waves combined with a high incidence of southeasterly waves. The study shows that many factors, including natural forcing factors and human activities, have to be taken into account when explaining saltmarsh development. [KEYWORDS: Lateral saltmarsh erosion; Vertical sediment accretion; Land claim; Wind/wave climate; Sea level; Thames]

Item Type:Article
Institutes:Nederlands Instituut voor Ecologie (NIOO)
ID Code:11596
Deposited On:23 Nov 2011 01:00
Last Modified:24 Apr 2012 16:33

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