Human influence and the changing geomorphology of Mediterranean deltas and coasts over the last 6000 years: From progradation to destruction phase?

Comparison of Coastal Vulnerability Index applications for Barcelona Province

Managing coastal erosion under climate change at the regional scale

In the present work, the case of the Carmenes del Mar resort (Granada, Spain) is shown. It can be considered one of the most extreme examples on the Mediterranean coast of severe pathologies associated with urban development on coastal landslides. The resort, with 416 dwellings, was partially built on a deep-seated landslide which affects a soft formation composed of dark graphite schists. In November 2015, the City Council officially declared a state of emergency in the resort and 24 dwellings have already been evacuated. We have used two remote sensing techniques to monitor the landslide with the aim of identifying and measuring a wide range of displacements rates (from mm/year to m/year): (1) PSInSAR, exploiting 25 ENVISAT SAR images acquired from May 2003 to December 2009, and (2) photogrammetry, considering the output from two Unmanned Aerial Vehicle (UAV) flights made in June 2015 and January 2016 and the outdated photos from a conventional flight in 2008. The relationship between the geology of the site, data from PS deformation measurements, building displacements, rainfall and damage observed and their temporal occurrence allows a better understanding of the landslide kinematics and both the spatial and temporal evolution of the instability. Results indicate building displacements of up to 1.92 m in 8 years, a clear lithological control in the spatial distribution of damage and a close relationship between the most damaging events and water recharge episodes (rainy events and leaks from swimming pools and the water supply network). This work emphasises the need to incorporate geohazards into urban planning, including policies to predict, prepare for and prevent this type of phenomenon.

/pdf/the-combined-use-of-psinsar-and-uav-photogrammetry-ywatd3ecbr.pdf

The combined use of PSInSAR and UAV photogrammetry techniques for the analysis of the kinematics of a coastal landslide affecting an urban area (SE Spain)

This study analyzes historical archives to produce a database of storm-induced coastal flooding in the French central part of the Bay of Biscay since 1500 AD. From this new database, 46 coastal floods have been reported for the last 500 years (1 event every 11 yr on average), which demonstrates the high vulnerability of this region to coastal flooding. The limitations of historical archives prevent concluding to a change in storminess over the period. The six largest coastal floods that occurred since 1900 are further investigated because numerous informations are available in terms of meteorological conditions as well as maximum water levels reached. Associated storm surges are also modeled using a simplified methodology, relying on a fully coupled wave and circulation modeling system directly forced by the available meteorological data. The analysis of modeling results and historical archives reveals firstly that several meteo-oceanic settings can lead to extensive coastal flooding in the studied area. The analyzed events allow distinguishing three main settings: (1) a small storm surge associated with the highest astronomical tidal levels, (2) a large storm surge, induced either by extreme winds or a particular sea-state and associated with high astronomical tidal levels and, (3) a large storm surge enhanced by extreme wave conditions. Second, maximum water levels reached during these 6 coastal floods were shown to be higher than the 100 years return period water level estimated in several recently published studies. This inconstancy can be explained mainly by the lack of extreme water level records in tide gauge datasets used in these previous studies. To a slightest degree, this study questions the validity of classical statistical approaches when analyzing extreme water levels data resulting from contrasting meteo-oceanic settings. It is concluded that historical archives combined with storm surge modeling could be a valuable approach to better estimate the return period of extreme sea levels and improve the understanding on the vulnerability of mixed-energy coastal environments such as the study area.

How frequent is storm-induced flooding in the central part of the Bay of Biscay?

Storm-induced damages along the Catalan coast (NW Mediterranean) during the period 1958-2008

This paper examines storm-induced morphological and hydrodynamic changes after a submerged and a detached breakwater were constructed at La Barceloneta beach (Barcelona, NW Mediterranean) in 2006–2007. The shoreline configurations before and after beach nourishment and the construction of the protective structures were compared using a video dataset comprising 29 storm events spanning the pre- (2001 to 2005, n = 17) and the post-breakwater situation (2006 to 2011, n = 12), and hydrodynamic modelling based on the SMC coastal modelling system. As a result of the protection works, La Barceloneta was subdivided into two beaches separated by an artificial salient. The analysis of shoreline response to storms has been improved by using the shoreline hyperbolic tangent fit to represent the beach planform. Comparing the pre- and post-breakwater situations on the basis of these shoreline fits facilitated the identification of beach rotation processes because interference by smaller-scale morphological features was eliminated (e.g. the formation, changes in shape or migration of mega-cusps). In the current post-breakwater situation, there is evidence for a change in the behaviour of the north-eastern beach triggered by the submerged breakwater built in 2007. Furthermore, a counter-clockwise beach rotation has occurred at the north-eastern beach, whereas the south-western beach has experienced a clockwise beach rotation. This morphodynamic behaviour is caused by a new, complex wave-induced circulation system comprising two dominant alongshore currents flowing in opposite directions. In contrast to the pre-breakwater situation, the alongshore component of the radiation stress does not accomplish beach rotation in the post-breakwater situation.

Storm-induced readjustment of an embayed beach after modification by protection works

Sancho-Garcia, A., Ruessink, B.G. and Guillen, J., 2011. Storm surge inundation along a multibarred beach.

/pdf/storm-surge-inundation-along-a-multibarred-beach-1kvnm7qv4h.pdf

Storm-Surge Inundation along a multibarred beach

Los fenomenos de inundacion en la costa durante temporales pueden causar danos severos a las estructuras costeras y son un factor de riesgo que debe ser cuantificado para una correcta gestion del medio litoral. La mayor parte de las observaciones existentes sobre los procesos de inundacion en playas se han realizado durante eventos de gran magnitud, asociados a largos periodos de retorno, pero son escasas las medidas sistematicas durante eventos intermedios. En el presente trabajo se cuantifica la inundacion de tres playas de la ciudad de Barcelona durante ocho temporales (Hs 3,4 m) ocurridos durante el periodo 2001 a 2007. En cada evento, se determino la posicion de la linea de costa cada hora mediante el empleo de imagenes de video, desde las horas previas al inicio del temporal hasta unas horas despues de que hubiese remitido. Estas observaciones se compararon con las predicciones de inundacion obtenidas mediante calculos teoricos basados en la altura de ola, el nivel del mar y la pendiente de la playa. En la mayoria de los eventos las observaciones y las estimaciones teoricas presentaron tendencias similares. Sin embargo, en algunos eventos la correlacion entre ambos datos fue baja debido a que los modelos teoricos sencillos utilizados no consideran una serie de procesos determinantes, como los mecanismos de rotacion o la erosion durante los temporales. En consecuencia, la capacidad predictiva de estos modelos es limitada.

Inundación de las playas de Barcelona durante temporales

The evaluation of coastal damage caused by storms is not straightforward and different approaches can be applied. In this study, damage caused by extreme storms is evaluated at a regional scale based on news information published in regional newspapers. The data derived from the news are compared with hydrodynamic parameters to check the reliability of this methodology as a preliminary” fast approach” to evaluate storm damage and to identify hotspots along the coast. This methodology was applied to the two most extreme storms ever recorded along the Spanish Mediterranean coast, which occurred in January 2017 and January 2020, severely impacting the coast and causing significant community concerns. The news information from different media sources was processed and weighted to describe the resulting erosion, inundation, sand accumulation, and destruction of infrastructures. Moreover, an accuracy index for scoring the quality of the information was proposed. In spite of some limitations of the method, the resulting regional coastal hazard landscape of damage provides a rapid overview of the intensity and distribution of the damage and enables one to identify the location of potential hotspots for the analyzed extreme storm events. The results show that estimated damage intensity is better related to maximum wave energy than cumulative wave energy during a storm, and that beach characteristics should also be included for understanding the distribution of coastal damage.

/pdf/the-use-of-news-information-published-in-newspapers-to-5ei5px8xcp.pdf

Amanda Sancho-García

Papers

Storm-induced damages along the Catalan coast (NW Mediterranean) during the period 1958-2008

Storm-induced readjustment of an embayed beach after modification by protection works

Storm-Surge Inundation along a multibarred beach

Inundación de las playas de Barcelona durante temporales

The Use of News Information Published in Newspapers to Estimate the Impact of Coastal Storms at a Regional Scale