Sandy tidal flat morphodynamics? Examples from Strangford Lough in Northern Ireland

GC Malvarez, F Navas, J Alcantara, DWT Jackson

Research output: Contribution to journalArticle

Abstract

In coastal research tidal flats are often classified and investigated in the context of estuarine dynamics due to the widely accepted view that tidal forces are the main responsible for their geomorphological evolution and that biological variables need to play a major role in its evolution. On the other hand coastal morphodyanmics deals mostly with geomorphological evolution of beaches taking a purely geological view on sediment dynamics. In this paper, a discussion is presented in relation to the adequate treatment of tidal flat research by illustrating various numerical and empirical methods used to address morphodynamics on the sandy tidal flats of Newtownards. Common to other sandy tidal flats, the intertidal shores of Newtownards in Strangford Lough (Northern Ireland) are affected by tidal flows (c 0.1 ms(-1)) given the average tidal range of 3.5 m and the action of wind generated waves over the fine grained siliciclastic sediments which frequently shows rippled Surfaces. The results from a wide range of investigations (previously published) that utilized mainly numerical modeling indicated that the flats of Newtownards characterized by a RTR (relative tidal range) factor of 2.3 to 7, are very sensitive to sediment redistribution due to combined water level / wave height effects which implies that wave energy dissipation due to bottom friction the primarily shoaling process during relative high energy events. Using empirical methods designed for beach morphodynamics research, it was found that (i) waves exceeded predicted values given short fetch under westerly winds, (ii) wave penetration was a parameter that proved extremely sensitive for sediment entrainment and was not sufficient to generate bedload sediment transport and (iii) further numerical simulations need to be conducted to achieve further understanding on the role of shoaling and spatial distribution of wave energy dissipation on the translating surf and nearshore zones to achieve a complete morphodynamic classification of these ultra-mega dissipative wave dominated environments.
LanguageEnglish
Pages160-167
JournalJournal of Coastal Research
Volume41
Issue numberSp. Is
Publication statusPublished - 31 Mar 2002

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morphodynamics
tidal flat
tidal range
wind wave
energy dissipation
wave energy
sediment
beach
estuarine dynamics
bottom friction
fetch
wave height
bedload
westerly
entrainment
sediment transport
water level
penetration
spatial distribution
modeling

Cite this

Malvarez, GC ; Navas, F ; Alcantara, J ; Jackson, DWT. / Sandy tidal flat morphodynamics? Examples from Strangford Lough in Northern Ireland. In: Journal of Coastal Research. 2002 ; Vol. 41, No. Sp. Is. pp. 160-167.
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Sandy tidal flat morphodynamics? Examples from Strangford Lough in Northern Ireland. / Malvarez, GC; Navas, F; Alcantara, J; Jackson, DWT.

In: Journal of Coastal Research, Vol. 41, No. Sp. Is, 31.03.2002, p. 160-167.

Research output: Contribution to journalArticle

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AU - Malvarez, GC

AU - Navas, F

AU - Alcantara, J

AU - Jackson, DWT

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N2 - In coastal research tidal flats are often classified and investigated in the context of estuarine dynamics due to the widely accepted view that tidal forces are the main responsible for their geomorphological evolution and that biological variables need to play a major role in its evolution. On the other hand coastal morphodyanmics deals mostly with geomorphological evolution of beaches taking a purely geological view on sediment dynamics. In this paper, a discussion is presented in relation to the adequate treatment of tidal flat research by illustrating various numerical and empirical methods used to address morphodynamics on the sandy tidal flats of Newtownards. Common to other sandy tidal flats, the intertidal shores of Newtownards in Strangford Lough (Northern Ireland) are affected by tidal flows (c 0.1 ms(-1)) given the average tidal range of 3.5 m and the action of wind generated waves over the fine grained siliciclastic sediments which frequently shows rippled Surfaces. The results from a wide range of investigations (previously published) that utilized mainly numerical modeling indicated that the flats of Newtownards characterized by a RTR (relative tidal range) factor of 2.3 to 7, are very sensitive to sediment redistribution due to combined water level / wave height effects which implies that wave energy dissipation due to bottom friction the primarily shoaling process during relative high energy events. Using empirical methods designed for beach morphodynamics research, it was found that (i) waves exceeded predicted values given short fetch under westerly winds, (ii) wave penetration was a parameter that proved extremely sensitive for sediment entrainment and was not sufficient to generate bedload sediment transport and (iii) further numerical simulations need to be conducted to achieve further understanding on the role of shoaling and spatial distribution of wave energy dissipation on the translating surf and nearshore zones to achieve a complete morphodynamic classification of these ultra-mega dissipative wave dominated environments.

AB - In coastal research tidal flats are often classified and investigated in the context of estuarine dynamics due to the widely accepted view that tidal forces are the main responsible for their geomorphological evolution and that biological variables need to play a major role in its evolution. On the other hand coastal morphodyanmics deals mostly with geomorphological evolution of beaches taking a purely geological view on sediment dynamics. In this paper, a discussion is presented in relation to the adequate treatment of tidal flat research by illustrating various numerical and empirical methods used to address morphodynamics on the sandy tidal flats of Newtownards. Common to other sandy tidal flats, the intertidal shores of Newtownards in Strangford Lough (Northern Ireland) are affected by tidal flows (c 0.1 ms(-1)) given the average tidal range of 3.5 m and the action of wind generated waves over the fine grained siliciclastic sediments which frequently shows rippled Surfaces. The results from a wide range of investigations (previously published) that utilized mainly numerical modeling indicated that the flats of Newtownards characterized by a RTR (relative tidal range) factor of 2.3 to 7, are very sensitive to sediment redistribution due to combined water level / wave height effects which implies that wave energy dissipation due to bottom friction the primarily shoaling process during relative high energy events. Using empirical methods designed for beach morphodynamics research, it was found that (i) waves exceeded predicted values given short fetch under westerly winds, (ii) wave penetration was a parameter that proved extremely sensitive for sediment entrainment and was not sufficient to generate bedload sediment transport and (iii) further numerical simulations need to be conducted to achieve further understanding on the role of shoaling and spatial distribution of wave energy dissipation on the translating surf and nearshore zones to achieve a complete morphodynamic classification of these ultra-mega dissipative wave dominated environments.

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