Franchissement et migration des cordons de galets par rollover. Impact de la tempête du 10 mars 2008 dans l’évolution récente du Sillon de Talbert (Côtes-d’Armor, Bretagne)

Stéphan, Pierre; Suanez, Serge; Fichaut, Bernard

doi:10.4000/norois.3252

Cited by 15 publications

(6 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It is possible, therefore, that high-energy events that contribute to the beach crest construction are characterized by long swell waves associated with storm tracks displaced northwards, that is, with conditions typically associated with a positive NAO. Stéphan et al (2010) have stressed that phases of morphogenic activity on the Sillon de Talber (Côtes-d’Armor, Brittany), and also identified on other coastal areas along the Brittany coastline, could have been related to oscillations of the WNAO index, suggesting that increased morphogenetic activity seems to coincide with positive WNAO index. To verify this hypothesis, we used the SIMAR-44 dataset (Spanish Port Authority) from the Hindcast of Dynamic Processes of the Ocean and Coastal Areas of Europe (HIPOCAS) project, a hindcast of waves from 1958 to 2001 (Guedes-Soraes, 2008), and a monthly NAO index (provided by the Climate Analysis Section, National Center for Atmospheric Research (NCAR); Hurrell, 1995).…”

Section: Discussionmentioning

confidence: 90%

Late-Holocene storm imprint in a coastal sedimentary sequence (Northwest Iberian coast)

et al. 2014

View full text Add to dashboard Cite

A combination of sedimentological, geomorphological, and pedological methods has been used to study a late-Holocene sedimentary sequence in a rock coast sector from NW Spain, with the aim of relating it to storm events and their morphodynamic effects. The sequence contains two coarse beach layers at an elevation of 2.8–3.5 m above the present highest astronomical tide (HAT). Radiocarbon dating revealed that their deposition had begun during 1735–1590 cal. yr BP and has continued until the present. The entire beach system experienced considerable morphological change after 1320–1230 cal. yr BP, with a westward displacement of the beach and a retreat of the sedimentary cliff in the eastern section. The two beach layers seem to have been formed by vertical aggradation of clasts and sand during high-energy storm events, highlighting the role of these events in the formation of sedimentary sequences on the rocky coasts of mid-Atlantic Europe. The effects of a recent storm event, recorded in March 2008, and the results of wave calculations suggest that long swell waves were needed for the accretion of the clasts. Using a hindcast model of wave data, we found a positive correlation between the winter North Atlantic Oscillation (WNAO) index and the winter monthly mean wave height and peak period. While the 14C chronology of beach sedimentation coincides with known climatic periods dominated by a positive NAO index, these results point to the importance of high-energy events and the synergies between past and present processes in the recent evolution and the morphodynamics of rock coast environments.

show abstract

Section: Discussionmentioning

confidence: 90%

Late-Holocene storm imprint in a coastal sedimentary sequence (Northwest Iberian coast)

et al. 2014

View full text Add to dashboard Cite

show abstract

“…Cette comparaison est d'autant plus aisée que de nombreux sites présents dans cette étude faisaient déjà l'objet d'un suivi topo-morphologique à l'époque ; gardons toutefois à l'esprit que nous comparons ici l'impact érosif d'un seul événement avec une série de tempêtes. Ainsi, dans les Côtes d'Armor, le Sillon de Talbert avait reculé d'environ -22 m au maximum contre plus de -30 m cet hiver (Stéphan et al, 2010). En baie de Saint-Michel-en-Grève, le recul maximum des dunes avait atteint -18 m, notamment dans le secteur de Saint-Michel-en-Grève, contre -24,5 m cet hiver .…”

Section: Discussionunclassified

“…Comme l'ont montré Coco et al (2014), l'effet cumulé des tempêtes sur la morphologie des plages, notamment en matière d'érosion du rivage, n'est donc pas attesté au-delà d'un certain seuil. Sur les cordons de galets, les évolutions mesurées confirment quant à elles les schémas de fonctionnement morphodynamique régionaux d'ores et déjà établis pour ce type d'accumulation sédimentaire (Stéphan et al, 2010 ;Stéphan, 2011aStéphan, , 2011b. Les premiers épisodes de tempête de l'hiver constituent en quelque sorte les événements « préparateurs ».…”

Section: Discussionunclassified

“…10). Le recul le plus significatif est principalement intervenu durant la tempête du début du mois de février (entre -10 m et -15 m), selon le mécanisme de rollover ; ce dernier se traduit par un transfert de galets de la face avant en direction du revers sous l'effet du franchissement de la crête par les vagues de tempête (Stéphan et al, 2010). En revanche, l'épisode du début du mois de janvier a été peu morphogène, favorisant même l'exhaussement de la crête, visible au niveau du profil B.…”

Section: Recul Des Cordons De Galetsunclassified

See 1 more Smart Citation

Bilan des tempêtes de l’hiver 2013-2014 sur la dynamique de recul du trait de côte en Bretagne

Blaise¹,

Suanez²,

Stéphan³

et al. 2015

geomorphologie

Self Cite

View full text Add to dashboard Cite

International audienceBetween December 2013 and March 2014, a cluster of about 12 storm events hit the coast of Brittany with an exceptional frequency. It was in February that these storm events were the most frequent and particularly virulent. The significant wave heights measured off Finistère reached respectively 12.3 m and 12.4 m during Petra and Ulla storms on February 5 and 14. However, analysis of hydrodynamic conditions shows that only three episodes promoted extreme morphogenetic conditions because they were combined with high spring tide level. The first one occurred on January 1rst to 4, it was followed by events from February 1rst to 3, and March 2-3. During these three extreme events observed tide levels were above highest astronomical tide level (HAT). Maximum surge level (0.97m) was reached during Ulla storm of February 14-15. For comparison, we must go back in the winter of 1989-90 to find such extreme storm frequency. High frequency topomorphological measurements were achieved on more than ten coastal zones distributed around Brittany peninsula to assess the effects of these storms on shoreline erosion. They show that during the first phase (December-January), meeting it's climax from 1rst to 4th January 2014, shoreline erosion has been limited, with the exception of southern Brittany. This is due to the SW orientation of waves. For all monitoring sites, it has averaged -2.7m, the averaged minimum equal to 0.6m, and the averaged maximum at -6.20m. During the second phase from mid-January to mid-February, reaching it's climax on 1-2 of February storm corresponding to the most morphogenetic event of the winter, the average of shoreline retreat reached -4.2m, the averaged minimum reached approximately -1.5m, the averaged maximum -9.5m. It is essentially the Northern and Western coast of Brittany that experienced largest shoreline retreat due to W-NW storm wave orientation. During the third and last phase, running from mid-February to mid-March, and characterized by the March 2-3 extreme morphogenetic event, shoreline retreat was very low. It reaches -1m on average, for an averaged minimum of -0.6m and an averaged minimum of -1.9m. Considering the whole winter 2013-14 period, shoreline erosion for all monitoring sites reached -6.3m on average, with a minimum of about -0.2 m and a maximum of -30.1m. Depending on the type of environment, it appears that the dunes have retreated the most, followed by gravel or sandy barriers; the lowest erosion rates concern beaches backed by low cliffs cut in highly consistent materials such as periglacial deposits (head). Considering the three morphogenous episodes, the morphological response in terms of shoreline retreat of beaches and barriers was different. Storm occurring at the beginning of February induced the largest erosive rates partly explained by the large morphological sensitivity of beaches and barriers which were weakened by the previous storm events in the beginning of January. Conversely, the storm of March induced very few impacts. These elements show...

show abstract

“…Suanez, Stéphan, Floc'h, Autret et al (2018) indicated that storm events, combined with high spring tide levels, control more than 95% of this retreat due to catastrophic overwash/inundation processes (Figures 3b and c). This was the case during the Johanna storm of 10 March 2008, when the maximum spit retreat reached −22 m (Stéphan et al, 2010). It was also the case during the stormy winter of 2013–2014, when the maximum spit retreat reached −30 m (Blaise et al, 2015).…”

Section: Study Sitementioning

confidence: 93%

Catastrophic overwash and rapid retreat of a gravel barrier spit during storm events (Sillon de Talbert, North Brittany, France)

Suanez

Stéphan

Autret

et al. 2022

Earth Surf Processes Landf

Self Cite

View full text Add to dashboard Cite

The morphodynamic functioning of the Sillon de Talbert gravel barrier spit is analysed using a high-frequency survey carried out between September 2012 and December 2019. It is based on beach profile measurements along two transects, modelling offshore wave data (WW3), tide gauge records, and shallow waves and water levels recorded in the intertidal zone. A barrier retreat of À23 to À30 m over the 7-year survey (i.e. À3.3 to À4.3 m yr À1 ) is measured. This retreat is not related to long-term sea level rise (macroscale of 10 2 -10 3 yr), but to mesoscale (10 0 -10 2 yr) morphogenic events combining storm wave and high spring tide. Over 87-90% of the barrier retreat is due to three significant events (1-2 February 2014, 9 February 2016, and 3 January 2018). The storm impact scale model of Orford and Carter is tested. The estimation of the wave runup for the calculation of extreme water levels [i.e. peak overflow elevation (O e ) component] is based on the calibration of an equation performed from in-situ measurements of the swash elevation. The flow depth (O d,q ) overtopping the crest of the barrier (B h ) is thresholded by taking into account the morphological response of the barrier in order to define regimes corresponding to overtopping, discrete overwash, and sluicing overwash. While the Orford and Carter model is generally successful in reproducing the morphodynamic evolution of Sillon de Talbert, the wave energy flux (F) must be considered as an additional parameter in order to improve the fit of the model, so far as it contributes in some cases to change the morphodynamic regime. Thus, the wave energy flux constitutes a key component in the quantification of the water flow across the barrier (O d,q ) corresponding to the hydrodynamic forcing of the model, which becomes (O d,F ).

show abstract

Franchissement et migration des cordons de galets par rollover. Impact de la tempête du 10 mars 2008 dans l’évolution récente du Sillon de Talbert (Côtes-d’Armor, Bretagne)

Abstract: Impacts morphogéniques des tempêtes Franchissement et migration des cordons de galets par rollover. Impact de la tempête du 10 mars 2008 dans l'évolution récente du Sillon de Talbert (Côtes-d'Armor, Bretagne)

Cited by 15 publications

References 30 publications

Late-Holocene storm imprint in a coastal sedimentary sequence (Northwest Iberian coast)

Late-Holocene storm imprint in a coastal sedimentary sequence (Northwest Iberian coast)

Bilan des tempêtes de l’hiver 2013-2014 sur la dynamique de recul du trait de côte en Bretagne

Catastrophic overwash and rapid retreat of a gravel barrier spit during storm events (Sillon de Talbert, North Brittany, France)

Contact Info

Product

Resources

About