Vulnerability of sandy coasts to climate variability

Abstract

The main objective of the VULSACO (VULnerability of SAndy COasts to climate change and anthropic pressure) project was to investigate present day and potential future vulnerability of sandy coasts at the 2030 horizon, i.e. on a time scale related to climate variability. The method, based on a multidisciplinary approach bringing together geologists, geographers, physicists, social psychologists, engineers and stakeholders, was structured around 4 axes: field data analysis; numerical modelling; analysis of governance and stakeholder perceptions; and development of vulnerability indexes. This approach was designed to investigate vulnerability at a local scale and was applied to 4 contrasting beaches located in France: Sète Lido (Mediterranean Sea), Truc Vert and La Tresson beaches (Atlantic Ocean), and Dewulf (English Channel). The results focus on decadal and multi-annual beach trends at the Truc Vert beach site. There is almost no trend in beach volume at Truc Vert beach, although there is a variation in this parameter on a cycle of 2 to 3 yr, with variations related to wave energy and probably to indexes of climate variability. Numerical modelling identified the sensitivity of beach responses to changes in wave height and direction, especially in terms of subtidal morphology and the potential development of shoreline instability. Together with the observed offshore wave angle at the Biscay Buoy, these model results suggest that a potential change in wave angle due to climate variability could significantly modify the bars' morphology. The combination of data analysis and numerical modelling contributed to the development of vulnerability indexes designed for sandy coasts, which take into account climate-dependant variables such as waves. This allowed the differentiation of the sites in terms of vulnerability to erosion: Sète Lido and Truc Vert beach were the most and least vulnerable sites, respectively. These indexes help in identifying the dominant components of beach vulnerability, and provide potential for the study of how anthropogenic factors affect vulnerability. The study of stakeholder perceptions and decision-making with regard to climate-related risk also highlighted potential anthropogenic effects on beach vulnerability, and identified possible site-specific outcomes.

An abrupt change in winds that may radically affect the coasts and deep sections of the Baltic Sea

“…Wave records and analyses of wave-driven coastal processes often provide a better option to reveal, visualise and quantify these changes. While in the open ocean the rotation of the wave climate is usually confined to a few degrees (Hemer et al 2013b, Idier et al 2013, for regions that are sheltered from remote swells, these changes are more locally driven and can be much greater (Soomere & Räämet 2011).…”

Coastal vulnerabilities under the deliberation of stakeholders: The case of two French sandy beaches

“…1). This choice was based on differences in terms of hydrodynamic and socio-economical characteristics: these two sites have different patterns of morphological, physical, space occupation and utilization characteristics (Idier et al, 2013).…”

“…It was expected that, based on their different local characteristics, stakeholders would favor, in the different sites, different courses of action to the risk of marine submersion in face of an unusually strong, yet plausible, storm (Idier et al, 2013). In contrast with Tol et al (2006), the scenarios used in the workshops here described are not 'worst-case' scenarios for two reasons.…”

Socio-economic Impacts—Coastal Management and Governance

“…In 2013, the Conseil National de la Mer et des Littoraux was installed for the exchange of views and experience among concerned authorities and civil organisations; the Conseil will contribute to the development of a national coastal management strategy. Specific strategies for coastal adaptation in view of climate change are still in a study phase (Idier et al 2013).…”