CLIMATE CHANGE AND BEACHES DESTRUCTION IN THE MEDITERRANEAN AREA  

Valerio Buonomo⁽¹⁾; Franco Ortolani⁽¹⁾; Silvana Pagliuca⁽²⁾

(1) department of Planning and Science of the Territory, University in Naples Fred II, Naples, Italy; fortolan@unina.it

(2) ISAFOM, CNR, Ercolano, Naples, Italy; pagliuca@ispaim.na.cnr.it  

KEY WARDS: climate change, littoral evolution, Mediterranean Area 

The beaches constitute the outcropping part of a geological prism, constituted by sandy/gravelly sediments, accumulated in the last thousand of years (Holocene) in concomitance with eusthatic sea waters rise, started around 15.000 years ago. 

The holocene coastal sediments can have a varying thickness from 15 to over 30 m along the shores that delimit the alluvial lowlands; the thickness is generally smaller along the Pocket Beach.   

The main result achieved with geoarchaeological research consists in the identification of cyclicity (period of about 1000 years) of the major climate and environmental changes that have resulted in real environmental crises lasting between 100 and 200 years in the Mediterranean area (figure 1). There is clearly to close correlation between climatic and environmental changes and solar activity (concurrence of prolonged maxima of solar activity and warm increased greenhouse effect periods and concurrence of repeated minima of solar activity and cold periods, such as the Little Ice Ages).

Figure 1

Instrumental data chiefly concerning the last 150 years show, in the Mediterranean Area, consistently close correlation between environmental variations (increase in solar activity and temperatures and changes in the quality and quantity of rainfall). On the basis of scientific data acquired with geoenvironmental research conducted in the Mediterranean basin, it is possible to predict that the most serious environmental changes expected in coastal areas. 

During the warm periods (temperatures increased by 1-2° C) the coastal zones were affected by desertification up to latitude of about 42° N (Roman increased "Greenhouse Effect", 100-300 A.D.; Medieval or Crusades increased "Greenhouse Effect", 1100-1270 A.D.).  

The littorals with silicoclastic sands where affected by severe erosion while the beaches with bioclastic sands where characterised by evident progradation. During the decreases in temperatures the areas of the alluvial plains subject to human impact and settlements were affected by an accumulation of huge volumes of sediments with consequent aggradation and progradation of the coastlines in the northern part of the Mediterranean while severe erosion occurred along the beaches with bioclastic sands of the southern part (Archaic Little Ice Age, 500-300 B.C.; Dark Age Little Ice Age, 500-750 A.D.; Little Ice Age, 1500-1830 A.D.).  

It is possible to predict that the beach erosion, prevalently caused by the climate variation, will be active for 150 years at least.  

Figure 2

Many thousands of kilometres of the Mediterranean coastline are affected by serious erosion which undermines not only the anthropised area, that has taken place up to few metres from the sea, but also the social and economic structure of entire regions whose economy is largely based on seaside tourism.  

It is undeniable, in fact, that coastline economy based on quality tourism, fostered by beautiful beaches, has contributed to the improvement of the social and economic position of the coastal regions.  

The beach erosion, consequently, represent a direct economic danger for the national and regional economic condition. 

Without effective and coordinated planning of the safeguarding, improvement and protection of the coastal areas, deterioration accentuated by predictable defence work made necessary by local emergency situations, will become more and more seriuos.  

The economic importance of the beaches is increased especially in the last 50 years in concomitance with the aggravation of the erosion.  

The palaeoenvironmental reconstructions put in evidence that the actual period of climatic variation represents the period of transition between the Little Ice Age and the following increase of the Greenhouse Effect, as cyclically and naturally is already verified in the past millennia (figures 1 and 2). 

An impact of notable importance interests the shores. It is evident that for the first time, in the last 1000 years, the man is found to face a natural, serious and general problem with a consistent negative impact on the environment and on the economy: that of the erosion and destruction of the beaches.  

The construction of the shores has happened during the cold-humid periods, that is during the past Little Ice Ages. The last natural nourishment is occurred between 1500 and the end of 1800 (figure 1).  

In Italy, particularly, the shores fed by sediments by the rivers have been supplied abundantly primarily between the beginning of 1700 and the end of 1800. From the beginning of 1900 the natural feeding has been more and more progressively scarce and the beaches have begun to "to grow thin" especially in correspondence of the delta areas of the rivers where the erosive phenomenons have, often, provoked the destruction of over 1000 meters of beach in the last 100 years. 

Big part of the beaches currently is insufficiently nourished of sand, only thanks to the erosion or “cannibalisation” of the sediments of the delta areas that are those interested by very serious erosion. 

  The search has reserved a particular attention to the individuation of the natural physical characteristics of the stable and not fed beaches, of elevated environmental and economic value, that characterize the coasts of Campania, Basilicata and Calabria, in Southern Italy. 

The acquired original environmental data have allowed to individualize suitable interventions (lasting nourishment) that allow to guarantee the defense and the geoenvironmental sustainable restauration of the Pocket Beachs, of varying length from some hundred meters to around 5 km, and of parts of long shores particularly interested by the erosion.  

The most evident and documented example of recent natural and lasting nourishment is represented by the beach of Vietri on the Sea (near Salerno in Campania Region) that in October 1954 was interested by the very rapid (few hours) accumulation of about 300.000-400.000 meters cubes of sediments transported by many debris flows that devastated the basin slopes in the night among 25 and 26 october. The deposits (gravels and sand) determined an instant nourishment that increased of over 100 meters the beach. From 1954 to today the beach (constituted by gravel with sandy matrix) has suffered a middle withdrawal of around 20 meters, as easily verifiable from the comparison of the topographical maps and aerial photo.  

 The research confirmed that the gravelly-sandy beaches similar to those of Vietri on the Sea, characterising the Amalfi coast and the Cilento (Southern Campania), the Maratea coast (Basilicata Region), and the Calabrian coast, are the most stable; in fact, the coarse sediments, heavier than the sand, are not eroded and dispersed towards the open sea by the tides induced by the strong sea storms. 

In relationship to the climatic variation the erosion of the beaches will last at least 100 - 150 years.  In this picture, a role of primary importance is represented by the individuation of the "streets of concentrated oblique dispersion" of the sand, with the purpose to mitigate the losses, especially in the Pocket Beach. In fact, our researches have pointed out that the longshore sand transport is transformed in oblique sand dispersion in corrispondence of natural and artificial change of the beach morphology. 

The most meaningful data to be kept in mind to individualize lines of intervention to preserve and to restore, in lasting way, the beaches, are the followings: 

- the last natural nourishment is occurred between 1500 and the end of 1800.  

- the beaches, currently, are partially and insufficiently fed of sand from the river; there is a partial feeding, within the shore, thanks to the erosion or “cannibalisation” of the sediments of the delta areas. 

- the period in which erosion prevails, like the present one, constitutes a multicentennial natural phase within the evolution of the beaches. 

- in relationship to the climatic variation, the erosion of the beaches will last at least 100-150 years. The climatic variation, as happened in past,  should behave an increase of the winds of southern origin and a consequent modification of the transport of the sediments along the shore (that is from the southern quadrants toward the northern ones). 

- the artificial protection of the long shore anthropised environment reduce the cliff erosion and consequently the sediment feeding;                                                                    - the artificial beach nourishments with sand are very expensive and not lasting; 

- the marine sands layers are absolutely insufficient for the nourishment of the various thousand of kilometers of shores interested by the erosion. 

- in correspondence of morphological interruptions of the beaches, natural (for example promontories) or artificial (docks), the sand transported longshore is dispersed  irreversibly toward the open sea. 

 The destruction of the beaches can effectively be opposed, and in lasting way, without altering the beauty of the beaches, only artificially supplying the shores of sediments.  

Till now have been performed various artificial nourishment of sand. Nobody has been lasting despite the elevated cost. The nourishment with sand would be the ideal intervention to effect, repeatedly.

Figure 3 – Rapid beach erosion in the touristic coast of the Cilento Natural National Park

 The true problem is represented by the elevated cost of the intervention, from the limited duration in the time and from the lack of marine layers of sandy sediments to satisfy the various thousand of kilometers of beach seriously affected by the erosion.   

Only in the Lazio, Liguria and Tuscany the requirement esteemed, within the European project Beachmed, is over 150 million meters cubes of sand for the reconstruction and 1,7 million meters cubes the year for the maintenance.

Considered the gravity and the predictable duration of many tens of years of the coastal erosion, the interventions of restauration of the beaches must be based on the followings aspects:  a - immediate realization of the intervention; b - contained cost of the  intervention (with interventions also performed with a sinergy between public institutions and privacies) through interventions inspired to the naturalistic engineering; c - restoration of lines of shore already existed in past; d - reconstruction of natural coastal morphologies without emerged or submerged artificial barriers ; e - duration of many tens of years of the intervention of restauration and nourishment. 

In the figures 3 and 4 area evidenced some example of rapid change of touristic and famous beaches along the Tirrhenian coast of Campania and Basilicata Region.

Figure 4 – Very rapid change of the littoral morphology in the touristic coast of Maratea, Basilicata, Southern Italy