Kenneth Pye
Associates
Ltd.
Scientific Research,
Consultancy and Investigations
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Patterns, rates and possible causes of saltmarsh erosion in the Greater Thames area (UK)
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Abstract 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. 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 nineteenth century in the Medway and Blackwater Estuaries, followed by other estuaries in the Greater Thames region at the beginning of the twentieth century. Especially the outer estuaries and the wider parts of the inner estuaries have experienced erosion. Erosion has been modest in wave-sheltered areas, e.g. the Colne and inner Crouch. In the 1960s and, more widely, 1970s, a phase of rapid erosion took place, with erosion rates of up to ca 16 ha a-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 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. Contact us to obtain a PDF version of this paper (574 KB). |
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