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A morphological investigation of marine transgression in estuaries

A morphological investigation of marine transgression in estuaries
A morphological investigation of marine transgression in estuaries
The landscape setting for an estuary varies widely and is an important aspect of determining how they evolve. This paper focusses on alluvial estuaries in river valleys and how they respond to sea level rise. We examine the implications of marine transgression, as a response to sea level rise, where the estuary moves upwards and landwards to maintain its position in the tidal frame (so-called “stratigraphic rollover”). Here we encapsulate such kinematic movement of the estuary morphology using a ‘morphokinematic’ model, to assess the potential response to sea level rise and sediment supply. The model of the estuary form includes a single convergent channel, intertidal and surrounding flood plains (the valley) and allows the relative importance of the space available for deposition of sediments, the accommodation space, to be investigated as a function of rates of sea level rise and sediment supply. The transgression of the system is determined using a sediment mass balance, taking account of any supply from the river and marine environment. Model results confirm that the transgression distance, measured as the distance the entity moves landward, varies in proportion to the change in accommodation space, which mainly depends on the flood plain area. As the size of the flood plain reduces, the transgression distance is less and the system becomes much more sensitive to changes in the rate of sea level rise, or changes in sediment supply. The greater demand for sediment when a flood plain is present results in greater cannibalisation of the estuary form (i.e. greater landward movement) to meet the sediment demand. When the flood plain is disconnected from the estuary, the synergistic relationship is lost and the accommodation space increases. The capacity for restoration will depend on the availability of sediment and the prevailing rate of sea level rise.
0197-9337
Townend, Ian
f72e5186-cae8-41fd-8712-d5746f78328e
Zhou, Zeng
f25e1390-6f07-4a32-9ebf-de15c07ded62
Guo, Leicheng
713f7dde-d88a-4f2c-9c66-7f9c6978ceb0
Coco, Giovanni
b5e273dc-1483-4764-9b54-d196075136e4
Townend, Ian
f72e5186-cae8-41fd-8712-d5746f78328e
Zhou, Zeng
f25e1390-6f07-4a32-9ebf-de15c07ded62
Guo, Leicheng
713f7dde-d88a-4f2c-9c66-7f9c6978ceb0
Coco, Giovanni
b5e273dc-1483-4764-9b54-d196075136e4

Townend, Ian, Zhou, Zeng, Guo, Leicheng and Coco, Giovanni (2020) A morphological investigation of marine transgression in estuaries. Earth Surface Processes and Landforms. (doi:10.1002/esp.5050).

Record type: Article

Abstract

The landscape setting for an estuary varies widely and is an important aspect of determining how they evolve. This paper focusses on alluvial estuaries in river valleys and how they respond to sea level rise. We examine the implications of marine transgression, as a response to sea level rise, where the estuary moves upwards and landwards to maintain its position in the tidal frame (so-called “stratigraphic rollover”). Here we encapsulate such kinematic movement of the estuary morphology using a ‘morphokinematic’ model, to assess the potential response to sea level rise and sediment supply. The model of the estuary form includes a single convergent channel, intertidal and surrounding flood plains (the valley) and allows the relative importance of the space available for deposition of sediments, the accommodation space, to be investigated as a function of rates of sea level rise and sediment supply. The transgression of the system is determined using a sediment mass balance, taking account of any supply from the river and marine environment. Model results confirm that the transgression distance, measured as the distance the entity moves landward, varies in proportion to the change in accommodation space, which mainly depends on the flood plain area. As the size of the flood plain reduces, the transgression distance is less and the system becomes much more sensitive to changes in the rate of sea level rise, or changes in sediment supply. The greater demand for sediment when a flood plain is present results in greater cannibalisation of the estuary form (i.e. greater landward movement) to meet the sediment demand. When the flood plain is disconnected from the estuary, the synergistic relationship is lost and the accommodation space increases. The capacity for restoration will depend on the availability of sediment and the prevailing rate of sea level rise.

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Accepted/In Press date: 15 December 2020
e-pub ahead of print date: 25 December 2020

Identifiers

Local EPrints ID: 445651
URI: http://eprints.soton.ac.uk/id/eprint/445651
ISSN: 0197-9337
PURE UUID: 4b80c2b1-1fa5-4c9a-8477-d67853708863
ORCID for Ian Townend: ORCID iD orcid.org/0000-0003-2101-3858

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Date deposited: 05 Jan 2021 17:31
Last modified: 26 Nov 2021 02:45

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Contributors

Author: Ian Townend ORCID iD
Author: Zeng Zhou
Author: Leicheng Guo
Author: Giovanni Coco

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