Bar Migrations on a Macrotidal Ebb Delta over a Period of Six Years Using Lidar Survey

Bas, Xavier Pellerin Le; Levoy, Franck

doi:10.2112/si85-030.1

Cited by 4 publications

(5 citation statements)

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“…The role of swash bars in the development of sandy barrier spits has been studied in some macrotidal inlets (Robin & Levoy, 2007; Robin et al., 2009a, 2009b; Montreuil et al., 2014; Le Bas & Levoy, 2018). These morphologies are integrated into the terminus of the sandy spits (Robin et al., 2009b, 2020) and have even been found in the architecture of some barriers in microtidal (Nielsen & Johannessen, 2009), mesotidal (Lindhorst et al., 2008, 2013; Costas & FitzGerald, 2011) and macrotidal environments (Fruergaard et al., 2020).…”

Section: Discussionmentioning

confidence: 99%

Morphostratigraphy of an active mixed sand–gravel barrier spit (Baie de Somme, northern France)

et al. 2022

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This study focuses on the architectural characterization of a mixed sand‐and‐gravel spit in relation to its multi‐decadal evolution. The spit, located in the Somme estuary in northern France, is a 5 km long sedimentary body made of several amalgamated ridges with a hooked terminus. Flint pebbles originating from the erosion of Cretaceous chalk cliffs and sands reworked from the tidal flat constitute the spit. Aerial photographs demonstrate that the spit formation started in the 1940s and document its growth through time. The architecture of the spit has been characterized by ground‐penetrating radar (GPR) investigation using 400 MHz and 900 MHz antennas. The GPR data are used to distinguish progradational, aggradational and transgressive geometries that are related to cross‐shore and longshore construction, respectively. Three main morpho‐stratigraphic domains characterize the spit from the root to the terminus: (i) a beach‐ridge domain mainly made of progradational structures; (ii) an intermediate domain formed by beach‐drift structures topped by deposits with cross‐shore geometries; and (iii) a spit‐terminus domain mainly composed of beach drift structures which incorporate sand deposits. At the scale of an individual ridge, high‐frequency GPR data indicates five types of sedimentary architectures associated with the evolution from a hook stage to the subsequent elongation stage. The overall development of the barrier spit is the result of complex interactions between wave and storm dynamics, potentially modulated by the variability of submersion time related to the 18.6 year tidal cycle, and anthropogenic activities including groyne construction and gravel reloading.

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Section: Discussionmentioning

confidence: 99%

Morphostratigraphy of an active mixed sand–gravel barrier spit (Baie de Somme, northern France)

et al. 2022

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“…This behaviour highlights the role of local, rather than offshore, wave characteristics in controlling ridge formation and evolution. Pellerin Le Bas and Levoy (2018) have shown that the large number of swash bars disturbs the waves refracted by the delta so much that the migration rate of these swash bars cannot be directly related to the hydrodynamic conditions. They proposed that the wave refraction, diffraction and sheltering effects induced by the numerous swash bars on the delta have a more significant role in bar migration rates than bar volumes or water height over the bar crests.…”

Section: Discussionmentioning

confidence: 99%

“…Five to 10 swash bars are commonly observed on the downdrift side, with lengths of 100 to 1000 m and widths of 50 to 200 m, representing 10 000 to 225 000 m 3 of sediment at any time (Pellerin Le Bas & Levoy, 2018). The foreshore on the updrift side is composed of coarse sand (mode: 0.5 to 1.0 mm) and the nearshore zone of medium sand (mode: 0.25 to 0.50 mm).…”

Section: Methodsmentioning

confidence: 99%

The formation and morphodynamics of complex multi‐hooked spits and the contribution of swash bars

Bas

Levoy

Robin

et al. 2021

Earth Surf Processes Landf

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Numerous studies have been devoted to recurved and hooked spits in micro-and meso-tidal environments, but none have really focused on the peculiar right-angle plan shape exhibited by some spit hooks. The morphodynamics of a complex multihooked spit in a macrotidal inlet in Normandy, France, have been investigated using aerial photographs and 12 topographic LiDAR surveys from 2000 to 2017, complemented by hydrodynamic data. Merville Spit is a 2.5 km-long hooked spit, composed of four 'nested' ridges each with a right-angle hook at its tip, that has developed in the vicinity of the sand-rich outlet of the Orne River. Monitoring of the two last ridges shows that ridge formation starts with the attachment of the tip of a swash bar to the fulcrum point of the previous ridge, and ends following its westward elongation and counter-clockwise rotation when its hook impinges on the Orne outlet.The main factor controlling ridge plan-view shape is swash bar dynamics in the vicinity of the spit. The offshore wave direction has no significant impact on ridge and hook behaviour due to the large number of swash bars on the ebb-tidal delta. Over the study period, between 5 and 10 swash bars massively assured sand supply to the upper foreshore, favouring the growth of existing ridges, but also enabling the building of a new ridge. The bars contribute to imparting hook right angles at the tips of the ridges by creating local wave refraction or by providing a sheltering effect. Strong tidal currents in the Orne channel act as a hydrodynamic barrier that stops hook elongation at the edge of the river's outlet. The similar behaviour of the two studied ridges has been synthesized into a new and original conceptual model of complex multi-hooked spit formation and evolution under the influence of swash bars.

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“…The movement of the swash bar crests is calculated using a dataset of 12 LiDAR surveys conducted between 2011 and 2017. The results showed that bars moved 350-400 meters along the ebb tidal delta between 2011 and 2017 (Le Bas and Levoy Levoy, 2018).…”

Section: Short-term Coastline Change Analysismentioning

confidence: 98%

Monitoring Coastline Dynamics Using Satellite Remote Sensing and Geographic Information Systems: A Review of Global Trends

Darwish

2024

Catrina: The International Journal of Environmental Sciences

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Bar Migrations on a Macrotidal Ebb Delta over a Period of Six Years Using Lidar Survey

Cited by 4 publications

References 0 publications

Morphostratigraphy of an active mixed sand–gravel barrier spit (Baie de Somme, northern France)

Morphostratigraphy of an active mixed sand–gravel barrier spit (Baie de Somme, northern France)

The formation and morphodynamics of complex multi‐hooked spits and the contribution of swash bars

Monitoring Coastline Dynamics Using Satellite Remote Sensing and Geographic Information Systems: A Review of Global Trends

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