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Causal Loop Analysis of coastal geomorphological systems

Causal Loop Analysis of coastal geomorphological systems
Causal Loop Analysis of coastal geomorphological systems
As geomorphologists embrace ever more sophisticated theoretical frameworks that shift from simple notions of evolution towards single steady equilibria to recognise the possibility of multiple response pathways and outcomes, morphodynamic modellers are facing the problem of how to keep track of an ever-greater number of system feedbacks. Within coastal geomorphology, capturing these feedbacks is critically important, especially as the focus of activity shifts from reductionist models founded on sediment transport fundamentals to more synthesist ones intended to resolve emergent behaviours at decadal to centennial scales. This paper addresses the challenge of mapping the feedback structure of processes controlling geomorphic system behaviour with reference to illustrative applications of Causal Loop Analysis at two study cases: (1) the erosion–accretion behaviour of graded (mixed) sediment beds, and (2) the local alongshore sediment fluxes of sand-rich shorelines. These case study examples are chosen on account of their central role in the quantitative modelling of geomorphological futures and as they illustrate different types of causation. Causal loop diagrams, a form of directed graph, are used to distil the feedback structure to reveal, in advance of more quantitative modelling, multi-response pathways and multiple outcomes. In the case of graded sediment bed, up to three different outcomes (no response, and two disequilibrium states) can be derived from a simple qualitative stability analysis. For the sand-rich local shoreline behaviour case, two fundamentally different responses of the shoreline (diffusive and anti-diffusive), triggered by small changes of the shoreline cross-shore position, can be inferred purely through analysis of the causal pathways. Explicit depiction of feedback-structure diagrams is beneficial when developing numerical models to explore coastal morphological futures. By explicitly mapping the feedbacks included and neglected within a model, the modeller can readily assess if critical feedback loops are included
systems analysis, behavioural model, emergent behaviour, feedback analysis, causal loop diagram, directed graph, high angle wave instability
0169-555X
1-28
Payo, A
755309ea-3c8a-4461-a533-d2fe25121d83
Hall, Jim W.
6084cd9f-ef4b-451c-8756-f0e8c14b26b5
French, Jon
37c7291b-e675-4dfe-a0df-ddf650668b4b
Sutherland, James
bf70e6ac-c2fb-4aa4-b470-ea2bd4003b6e
van Maanen, Barend
47cb6ae2-9baf-4f37-a138-067d72966597
Nicholls, Robert J.
85ca94ed-b373-43fa-aa62-e0f13b5eb080
Reeve, Dominic E.
e278f093-b56c-430b-a058-660aa4eabcbc
Payo, A
755309ea-3c8a-4461-a533-d2fe25121d83
Hall, Jim W.
6084cd9f-ef4b-451c-8756-f0e8c14b26b5
French, Jon
37c7291b-e675-4dfe-a0df-ddf650668b4b
Sutherland, James
bf70e6ac-c2fb-4aa4-b470-ea2bd4003b6e
van Maanen, Barend
47cb6ae2-9baf-4f37-a138-067d72966597
Nicholls, Robert J.
85ca94ed-b373-43fa-aa62-e0f13b5eb080
Reeve, Dominic E.
e278f093-b56c-430b-a058-660aa4eabcbc

Payo, A, Hall, Jim W., French, Jon, Sutherland, James, van Maanen, Barend, Nicholls, Robert J. and Reeve, Dominic E. (2015) Causal Loop Analysis of coastal geomorphological systems. Geomorphology, 1-28. (doi:10.1016/j.geomorph.2015.07.048).

Record type: Article

Abstract

As geomorphologists embrace ever more sophisticated theoretical frameworks that shift from simple notions of evolution towards single steady equilibria to recognise the possibility of multiple response pathways and outcomes, morphodynamic modellers are facing the problem of how to keep track of an ever-greater number of system feedbacks. Within coastal geomorphology, capturing these feedbacks is critically important, especially as the focus of activity shifts from reductionist models founded on sediment transport fundamentals to more synthesist ones intended to resolve emergent behaviours at decadal to centennial scales. This paper addresses the challenge of mapping the feedback structure of processes controlling geomorphic system behaviour with reference to illustrative applications of Causal Loop Analysis at two study cases: (1) the erosion–accretion behaviour of graded (mixed) sediment beds, and (2) the local alongshore sediment fluxes of sand-rich shorelines. These case study examples are chosen on account of their central role in the quantitative modelling of geomorphological futures and as they illustrate different types of causation. Causal loop diagrams, a form of directed graph, are used to distil the feedback structure to reveal, in advance of more quantitative modelling, multi-response pathways and multiple outcomes. In the case of graded sediment bed, up to three different outcomes (no response, and two disequilibrium states) can be derived from a simple qualitative stability analysis. For the sand-rich local shoreline behaviour case, two fundamentally different responses of the shoreline (diffusive and anti-diffusive), triggered by small changes of the shoreline cross-shore position, can be inferred purely through analysis of the causal pathways. Explicit depiction of feedback-structure diagrams is beneficial when developing numerical models to explore coastal morphological futures. By explicitly mapping the feedbacks included and neglected within a model, the modeller can readily assess if critical feedback loops are included

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GEOMOR-4967R2_reviewed_edited_amended.pdf - Accepted Manuscript
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More information

Accepted/In Press date: 31 July 2015
Published date: August 2015
Keywords: systems analysis, behavioural model, emergent behaviour, feedback analysis, causal loop diagram, directed graph, high angle wave instability
Organisations: Energy & Climate Change Group

Identifiers

Local EPrints ID: 381707
URI: http://eprints.soton.ac.uk/id/eprint/381707
ISSN: 0169-555X
PURE UUID: 883d6aa3-0997-40cd-a37d-2697558e704e

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Date deposited: 18 Sep 2015 13:28
Last modified: 15 Mar 2024 05:21

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Contributors

Author: A Payo
Author: Jim W. Hall
Author: Jon French
Author: James Sutherland
Author: Barend van Maanen
Author: Robert J. Nicholls
Author: Dominic E. Reeve

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