Guillaume Dodet

Extreme wave activity during 2013/2014 winter and morphological impacts along the Atlantic coast of Europe

Studies of coastal vulnerability due to climate change tend to focus on the consequences of sea level rise, rather than the complex coastal responses resulting from changes to the extreme wave climate. Here we investigate the 2013/2014 winter wave conditions that severely impacted the Atlantic coast of Europe and demonstrate that this winter was the most energetic along most of the Atlantic coast of Europe since at least 1948. Along exposed open-coast sites, extensive beach and dune erosion occurred due to offshore sediment transport. More sheltered sites experienced less erosion and one of the sites even experienced accretion due to beach rotation induced by alongshore sediment transport. Storm wave conditions such as were encountered during the 2013/2014 winter have the potential to dramatically change the equilibrium state (beach gradient, coastal alignment, and nearshore bar position) of beaches along the Atlantic coast of Europe.

A new climate index controlling winter wave activity along the Atlantic coast of Europe: The West Europe Pressure Anomaly

A pioneering and replicable method based on a 66-year numerical weather and wave hindcast is developed to optimize a climate index based on the sea level pressure (SLP) that best explains winter wave height variability along the coast of western Europe, from Portugal to UK (36–52 ∘ N). The resulting so-called Western Europe Pressure Anomaly (WEPA) is based on the sea level pressure gradient between the stations Valentia (Ireland) and Santa Cruz de Tenerife (Canary Islands). The WEPA positive phase reflects an intensified and southward shifted SLP difference between the Icelandic low and the Azores high, driving severe storms that funnel high-energy waves toward western Europe southward of 52 ∘ N. WEPA outscores by 25–150% the other leading atmospheric modes in explaining winter-averaged significant wave height, and even by a largest amount the winter-averaged extreme wave heights. WEPA is also the only index capturing the 2013/2014 extreme winter that caused widespread coastal erosion and flooding in western Europe.

Seasonal to Decadal Variability of Longshore Sand Transport at the Northwest Coast of Portugal

AbstractLongshore sediment transport (LST) is a major driver of coastal evolution. However, despite the recognition that it presents an unsteady behavior at the seasonal scale, the variability at longer term scales (interannual and decadal) is still far from being properly acknowledged. The present work contributes to the understanding of the seasonal to decadal variability of the LST, benefiting from recent developments in wave hindcast modeling. This work was developed for the northwest coast of Portugal, which is fully exposed to the highly energetic wave regime generated in the Northeast Atlantic Ocean that induces unusually large LST rates. Hindcast offshore waves, between 1953 and 2010, were used as offshore forcing to deduce LST estimates. The mean annual LST, between 1953 and 2010, shows an irregular and noncyclic pattern. Computed mean annual LST, for this coastal stretch, is around 1 million cubic meters directed to the south, with yearly averages ranging from 108,000 to 2.24 million m3 year−1 a...

Effect of inlet morphology and wave action on pollutant pathways and sediment dynamics in a coastal stream

Hydrodynamics and water renewal of intermittent coa stal streams are highly variable, at various time scales, due to the very active morphod ynamic behavior of their inlets. Due to this strong dynamics, the pathways of water-born e materials – and the consequences of contaminated discharges – can depend strongly on the morphology and environmental conditions. Predicting the fate of contaminants in these systems requires coupled numerical models accounting for the major physical and water quality processes. We aim at improving the understanding of the impact of inlet morphology and wave action on the pollutant and sediment pathways of th ese small coastal systems, based on a suite of calibrated and validated coupled models. T wo analyses, based on particle simulations, are presented to assess sediment dynam ics and pollutant pathways for several conditions. Results show that waves have a major effect on the fate of waterborne materials in the estuary. Wave-induced curren ts sweep away materials coming out of the estuary, while wave-induced setup has a prof ound effect on tidal propagation, water levels and velocities in the estuary, promoti ng he upstream transport of pollutants. 1 National Laboratory for Civil Engineering, Av. do B rasil, 101, 1700-066 Lisbon, Portugal; {aoliveira, afortunato, mguerreiro, xbertin, nbrune au, mfrodrigues, pfreire, lsimoes, gdodet, amendes}@lnec.pt. 2 Faculdade de Ciências da Universidade de Lisboa, Ca mpo Grande, Ed. C6, 1749-016 Lisboa, Portugal; {rtaborda, candrade, amasilva, cm antunes}@fc.ul.pt. 3 CIMA, Universidade do Algarve, Campus de Gambelas, Ed. 7, 8005-139 Faro, Portugal; cloureiro@ualg.pt.

Un indice climatique contrôlant les conditions de vagues en hiver le long de la côte atlantique européenne : WEPA (West Europe Pressure Anomaly)

1. CNRS/Univ. Bordeaux, UMR EPOC, Allée Geoffroy Saint-Hilaire, Pessac, France. bruno.castelle@u-bordeaux.fr 2. LETG-Brest Geomer UMR 6554 CNRS, Institut Universitaire Européen de la Mer (UBO), Plouzané, France. guillaume.dodet@univ-brest.fr 3. Coastal Processes Research Group, School of Biological and Marine Sciences, Plymouth University, UK. gerd.masselink@plymouth.ac.uk; timothy.scott@plymouth.ac.uk

Beach recovery from extreme storm activity during the 2013-14 winter along the Atlantic coast of Europe: BEACH RECOVERY FROM EXTREME STORM ACTIVITY

The storm sequence of the 2013/14 winter left many beaches along the Atlantic coast of Europe in their most eroded state for decades. Understanding how beaches recover from such extreme events is essential for coastal managers, especially in light of potential regional increases in storminess due to climate change. Here we analyze a unique dataset of decadal beach morphological changes along the west coast of Europe to investigate the post‐2013/14‐winter recovery. We show that the recovery signatureis site‐specific and multi‐annual, with one studied beach fully recovered after two years, and the others only partially recovered after four years. During the recovery phase, winter waves primarily control the timescales of beach recovery, as energetic winter conditions stall the recovery process while moderate winter conditions accelerate it. This inter‐annual variability is well correlated with climate indices. On exposed beaches, an equilibrium model showed significant skill in reproducing the post‐storm recovery and thus can be used to investigate the recovery process in more details.