Figure 4 - uploaded by Tristan B Guest
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(a) The overhead camera frame, with downward-looking camera to monitor the transport of painted tracer cobbles in the swash. The camera was elevated approximately 3 m above the bed. (b-d) Sample imagery captured by the camera during the development of a high tide berm (tide 19). The images represent intermediate and late stages of the berm's development, beginning with the initial deployment of the cobble tracers. The decreased number of cobbles visible in (d) is a result of burial.

(a) The overhead camera frame, with downward-looking camera to monitor the transport of painted tracer cobbles in the swash. The camera was elevated approximately 3 m above the bed. (b-d) Sample imagery captured by the camera during the development of a high tide berm (tide 19). The images represent intermediate and late stages of the berm's development, beginning with the initial deployment of the cobble tracers. The decreased number of cobbles visible in (d) is a result of burial.

Source publication
Article
Full-text available
On mixed sand–gravel beaches, impacts from gravel- and cobble-sized grains—mobilized by the energetic shorebreak—limit the utility of in situ instrumentation for measuring the small-scale response of the beach face on wave period time scales. We present field observations of swash zone morpho-sedimentary dynamics at a steep, megatidal mixed sand–gr...

Contexts in source publication

Context 1
... camera was mounted to a second instrument frame, consisting of a stationary base which could be moved with the changing shoreline position, and a movable arm which supported the camera allowing it to view the swash zone from a height of ca. 3 m without the frame base being in the image. The frame and camera are shown in Figure 4. The camera field of view at the beach surface was approximately 2.4 by 4.3 m, longshore by cross-shore. ...
Context 2
... camera's cross-shore field of view spanned y ≈ 3.5 to 7 m in local cross-shore coordinates, and contained almost entirely coarse berm material. Note that this is the station associated with the images in Figure 4. ...

Citations

... These insights remain limited by availability in time and quality of data. Indeed, wave breaking and swash were specifically shown to be linked with morphological processes especially for gravel beaches (Guest and Hay, 2021) although their variability is expected to be more significant at longer time scales (Almeida et al., 2014;Buscombe and Masselink, 2006;Karunarathna et al., 2012;Poate et al., 2013;Ratliff and Murray, 2014). ...
... Position, orientation, size, shape, and composition of assemblages are the result of antecedent conditions of sediment supply availability, and sediment sorting processes (Buscombe and Masselink, 2006). Their temporal variability could potentially be used as a proxy of surface sediment transport processes, as was demonstrated by Guest and Hay (2021) using remote sensing techniques applied on 14 days of high frequency video images, over a 2.7 m longshore span. ...
Article
Full-text available
This article aims to investigate the 3D morpho-sedimentary dynamics of two gravel beaches in relation to hydrodynamic forcing, using a multi-sensor approach. Study sites, namely Etretat and Hautot-sur-Mer, are both located in Normandy, France. Thus, they face similar wave conditions of the English channel's eastern side, with megatidal ranges and channelized wave orientations. However, they differ in gravel size (D50 Etretat = 5.2 cm; D50 Hautot-sur-Mer = 7.0 cm), vertical composition (Etretat is a purely gravel beach, Hautot-sur-Mer is a composite one with a low tide terrace) and wave exposure (Etretat is an embayed beach, oriented 47°N, Hautot-sur-Mer is a semi-open beach, oriented 71°N). Used data include shoreline positions automatically extracted from coastal Video Monitoring Systems (VMS) images between 2018 and 2020, wave data provided by the WaveWatch 3 model, and gravel size maps derived from UAV-imagery at different dates (one in Etretat, three in Hautot-sur-Mer). First, an Empirical Orthogonal Function (EOF) analysis was performed on the shoreline position data to extract the Principal Components (PC) describing mechanisms of morphological changes in the shoreline shape at different elevations (−2 to +3 m in Etretat and + 1 to +3 m in Hautot-sur-Mer). Four mechanisms spread within five PCs were found in Etretat: cross-shore translation (PC1), rollover (PC2), scale/elevation dependent rotation (PC3 and PC4) and breathing (PC5). Four PCs describing three mechanisms were identified in Hautot-sur-Mer: right-centered beach cell rotation (PC1), left-centered beach cell rotation (PC2), large scale rotation (PC3) and rollover (PC4). Interpretation of the PCs were supported by significant correlations with morphological parameters such as average beach width (BW), beach orientation angle (BOA) and beach slope (BS). The main mid-term morphological periods of variability include 2, 3, 5 and 8+ months in Etretat and 2, 3 and 6 months in Hautot-sur-Mer (all parameters included), which essentially corresponds to the variability of the wave energy. Finally, the analysis of surface grain size spatial variability revealed the presence of textural patterns with spatial and temporal variations in sorting and average grain size up to 1 cm in two months.