Contribution of storms to shoreline changes in mesotidal dissipative beaches: case study in the Gulf of Cádiz (SW Spain)

Abstract

Abstract. In this study an analysis of storminess and rates of shoreline change is performed and discussed jointly in four geomorphological units of the Gulf of Cádiz (SW Spain) for the period of 1956-2010. For this purpose, storm events are identified based on the following characteristics: wave height above 2.5 m, a minimum duration of 12 h and events with calm periods of less than 24 h were considered as a single event. Subsequently, energy parameters are determined in order to characterize storm-induced impacts. Conversely, geographic information system (GIS) tools are used to measure shoreline changes in aerial photographs and orthophotographs of each site, selecting the high water line as shoreline proxy. Each geomorphological unit is divided into different behavioural patterns according to recorded coastal changes, so that each one shows a particular behaviour.In general the variability of shoreline changes that is explained by storms and the relation between storm parameters and coastal changes present better results in exposed areas (Cádiz and Vistahermosa) than in sheltered areas (Valdelagrana spit barrier) because the former are more sensitive to storm impacts. On the contrary, in areas where there is no relation between coastal changes and storm parameters (Valdelagrana and Sancti Petri sand spit), it is suggested that anthropogenic factors are the main forcing agents determining shoreline behaviour. However, in these areas the storminess also modulates coastline recession by increasing erosion when the number of storms is high.

High-Resolution Interannual Evolution of the Dune Toe at a Mesotidal Barrier (Camposoto Beach, SW Spain)

“…The results present the perdurance of the already identified retreating trend of the system [44,[51][52][53], as well as an acceleration in this process for the area of Camposoto Beach, as the dune toe retreat registered in this area during the 10-year period spanning from 2008 to 2018 (−2.30 m/year) was doubled in comparison to the one presented by Del Rio et al [51] for the period from 1956 to 2008 over a wider area (an average of −0.9 m/year with maximum of 1.4 m/year). The reason for the observed differences could be methodological (different time scale resolutions) and/or physical (changes in the trend after a high-energy storm occurred in 2010, from which the beach could not fully recover).…”

“…A rollover process has been identified for the Sancti Petri spit with retreat rates of around 1 m per year [35,[43][44][45]. As a result, the migration of the sand spit has occurred landwards as sea storms have activated the overwash processes and deposited the eroded material behind the dunes [34,39].…”

Global coastal wave storminess

“…In fact, besides the energy impairing the coastline, i.e., the intensity of the wave storm, the duration of that extreme event is in fact what causes more impact on the coast 92 . The storm duration criterion has been chosen in previous studies according to different criteria, such as the time series resolution 32 , the duration of the tidal cycle 52 , 84 , 93 , 94 , or the minimum duration assumed to cause erosion damage in the coastline 31 , 53 , 95 . Here, we choose a single minimum storm duration of 12 h, for several reasons.…”

“…First, the use of a single criterion is the standard practice in regional studies 42 , 47 , 50 , 96 and it allows a homogenous comparison across coastal areas. Second, the selected minimum duration has been used in multiple studies, covering coastal regions affected by different storm wave climates, which encourage its use at global scale: Mediterranean Sea 50 , 96 – 99 , the Gulf of Mexico and the Caribbean Sea 47 , Eastern North Atlantic 31 , 52 , 84 , 93 , 95 , 99 , 100 , Western North Atlantic 88 , 100 , the Eastern North Pacific 94 , 99 and the Black Sea 101 . Third, this criterion captures long events, avoiding sparse weak events that may not cause coastal damage.…”

The Use of UAVs for the Characterization and Analysis of Rocky Coasts

“…As a first approach, variations in the cliff sector were analyzed for two years (2016-2018), detecting mass movements and variations in cliff profiles [52,55]. Moreover, in this case, variations in the cliff top were analyzed to estimate the evolution of the cliff during the aforementioned period using DSAS (Digital Shoreline Analysis System) [55], widely used in coastal studies [56][57][58]. In this sense, this type of study must be complemented with future field surveys by installing sensors to monitor soil humidity or by analyzing the flora and fauna of each site in order to understand their behavior and importance.…”