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Multi-timescale morphological modelling of a dune-fronted sandy beach

Harshinie Karunarathna Orcid Logo, Jennifer Brown, Antonia Chatzirodou, Pushpa Dissanayake, Paul Wisse

Coastal Engineering, Volume: 136, Pages: 161 - 171

Swansea University Author: Harshinie Karunarathna Orcid Logo

Abstract

Medium/long term trends (annual to decadal scale) of beach change are mostly used to make coastal management decisions. However, short term, extreme episodic events (short term) can erode the beach to exceed sustainable erosion thresholds thereby impacting long term trends of coastal change. Therefo...

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Published in: Coastal Engineering
ISSN: 0378-3839
Published: 2018
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa39004
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Abstract: Medium/long term trends (annual to decadal scale) of beach change are mostly used to make coastal management decisions. However, short term, extreme episodic events (short term) can erode the beach to exceed sustainable erosion thresholds thereby impacting long term trends of coastal change. Therefore, understanding coastal change at short and medium-long term (years to decades) timescales is essential to provide sustainable solutions to beach erosion. In this paper, we investigate and simulate the change of a beach-dune system for a megatidal coastline in the UK at storm timescale and at medium-long term timescale corresponding to sea level rise, in order to assess their significance in terms of beach management. The field site of choice is the Sefton coast, located in Liverpool Bay, United Kingdom. The approach used here involves process based modelling to determine storm-induced beach erosion and the application of modified Bruun Rule (Dean and Houston, 2016) to determine medium-long term evolution associated with climate change impacts. The application of the process-based model, XBeach, reveals that storm-induced short term beach erosion can be in the same scale or may surpass average medium/long term erosion thresholds and therefore, should be taken in to account when managing coastlines. Despite the complexities of the megatidal Sefton coast, the modified Bruun Rule proved to be capable of capturing long term beach profile change and assures that it can be confidently used to determine medium-long term beach-dune change due to sea level rise, once reliable estimates of longshore transport and sediment sources/sinks are made.
Item Description: The paper presents a novel combined process-based and behavioural coastal morphodynamic modelling approach for forecasting multi-timescale coastal change. This paper is a product of EPSRC FloodMEMORY (EP/K013513/1) and an Impact Acceleration Grant ‘Are simple estimates of coastal recession enough for sustainable coastal management?’ projects. The methodology developed in this paper led to NERC Mitigating hydro meteorological hazard impacts through transboundary river management in the Ciliwong River basin (NE/S003282/1) project and two invited talks in Ocean University China and Kanazawa University Japan.
Keywords: Morphology change; Bruun rule; XBeach; Sefton coast; Storm impact; Beach-dune erosion
Start Page: 161
End Page: 171