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The influence of shell transport on the morphology and erosion of a salt marsh : Hythe, Southampton Water

The influence of shell transport on the morphology and erosion of a salt marsh : Hythe, Southampton Water
The influence of shell transport on the morphology and erosion of a salt marsh : Hythe, Southampton Water

The present research has concentrated on the investigation of an intertidal area (Hythe intertidal flats) located in Southampton Water, Hampshire, UK.  The Hythe salt marshes are suffering significant erosion (1 to 3 m yr-1) and a major characteristic of its intertidal zone is the widespread presence of chenier deposits.  These deposits are composed largely of cockle shells (Cerastoderma edule) and are found on the salt marshes.  The process of abrasion acting on the seabed is occurring along the seaward edge of the salt marshes, where a well-defined cliff (approximately 1.5 m high) is observed.

Based on this background and on the significant input of cockle shells to the intertidal area of Hythe, this study has investigated the potential influence of shell movement on the erosion of intertidal (cohesive) beds and the resultant morphology.  These processes are investigated by combining in situ measurements and laboratory experiments.  The main objective of the investigation is to determine the contribution of shells moving as bedload to the erosion rates and morphological evolution of Hythe salt marshes.

Overall, the results showed that shell movement across Hythe intertidal flats can influence the geomorphology and erosion at the site.  The main mechanism of cliff erosion is the combination of wave attack and the abrasive effects of shell.  No seasonal pattern in bed level changes was observed.  Hence, bed erosion/stability appeared not to be controlled by biological fluctuations throughout the year, which indicates that the prevailing hydrodynamic processes are the main factors controlling bed behaviour of the Hythe intertidal flats.  Results from in situ measurements combined with laboratory experiments showed that shells (and potentially other debris, such as sand), moving as bedload, decrease the threshold and increase the erosion rate of cohesive beds.  Hence, shell-induced erosion can become an important parameter on the morphological evolution of a coastal area.

University of Southampton
Quaresma, Valeria da S
Quaresma, Valeria da S

Quaresma, Valeria da S (2004) The influence of shell transport on the morphology and erosion of a salt marsh : Hythe, Southampton Water. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The present research has concentrated on the investigation of an intertidal area (Hythe intertidal flats) located in Southampton Water, Hampshire, UK.  The Hythe salt marshes are suffering significant erosion (1 to 3 m yr-1) and a major characteristic of its intertidal zone is the widespread presence of chenier deposits.  These deposits are composed largely of cockle shells (Cerastoderma edule) and are found on the salt marshes.  The process of abrasion acting on the seabed is occurring along the seaward edge of the salt marshes, where a well-defined cliff (approximately 1.5 m high) is observed.

Based on this background and on the significant input of cockle shells to the intertidal area of Hythe, this study has investigated the potential influence of shell movement on the erosion of intertidal (cohesive) beds and the resultant morphology.  These processes are investigated by combining in situ measurements and laboratory experiments.  The main objective of the investigation is to determine the contribution of shells moving as bedload to the erosion rates and morphological evolution of Hythe salt marshes.

Overall, the results showed that shell movement across Hythe intertidal flats can influence the geomorphology and erosion at the site.  The main mechanism of cliff erosion is the combination of wave attack and the abrasive effects of shell.  No seasonal pattern in bed level changes was observed.  Hence, bed erosion/stability appeared not to be controlled by biological fluctuations throughout the year, which indicates that the prevailing hydrodynamic processes are the main factors controlling bed behaviour of the Hythe intertidal flats.  Results from in situ measurements combined with laboratory experiments showed that shells (and potentially other debris, such as sand), moving as bedload, decrease the threshold and increase the erosion rate of cohesive beds.  Hence, shell-induced erosion can become an important parameter on the morphological evolution of a coastal area.

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Published date: 2004

Identifiers

Local EPrints ID: 465375
URI: http://eprints.soton.ac.uk/id/eprint/465375
PURE UUID: 30edab83-75a5-4709-a9d6-839e326d9d7a

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Date deposited: 05 Jul 2022 00:40
Last modified: 05 Jul 2022 00:40

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Author: Valeria da S Quaresma

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