Contribution of storms to shoreline changes in mesotidal dissipative beaches. Case study in the Gulf of Cadiz (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 Cadiz (SW Spain), for the period 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. On the other hand, GIS tools are used to measure shoreline changes on 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 (Cadiz and Vistahermosa) than in sheltered areas (Valdelagrana spit barrier), as 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.

Deconvolving The Effects of Coastal Erosion and Sea-Level Rise in Assessing Shoreline Retreat Along Semi-Arid Urban Coasts

“…The Santa Ana and San Gabriel Rivers provide the total budget replenishment of natural sand for the coast. Damming in recent decades has obstructed sand transport to the beaches in Southern California by 47% from the total natural uvial sand yield, estimated at nearly 1.5 million cubic meters of sand annually [39]. Sea cliff armoring reduces the sand supplied to Southern California's beaches by another 10% of the natural sand supply, accounting for more than 26,750 cubic meters annually, which represents less than 7% of the total sand input [39].…”

“…The small study area of the Corona del Mar's pocket beach spans along the San Pedro beach compartment and Laguna littoral sub-cell, where ~59% of the sediment budget is supplied by anthropogenic beach nourishment [39]. The Santa Ana and San Gabriel Rivers provide the total budget replenishment of natural sand for the coast.…”