geosciences

Article Beach in the Gulf of in Response to the Trapping of Longshore Drifting of the Gulf of Napoli (Southern )

Micla Pennetta ID

Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse (DiSTAR), Università degli Studi di Napoli “Federico II”, 80138 , Italy; [email protected]

 Received: 10 May 2018; Accepted: 25 June 2018; Published: 27 June 2018 

Abstract: The results of this study have allowed verification that longshore transport along the coast of Napoli Gulf () takes place from Northwest to Southeast. The current analysis describes the results of an integrated sedimentological and geomorphological study of the Neapolitan coastal area. A sedimentological and morphosedimentary study was carried out by bathymetric survey and sampling of bottom sediments. The analysis of modal isodensity curves shows that all the sediments are moved from NW to SE by longshore currents parallel to the coastline. The morphological evolution of the Castellammare di Stabia Gulf coastal area, based on historical coastline changes, starts from 1865, when the sandy littoral was wide and in its natural state. Since the construction of the harbor in 1871, sediments transported by a NW-SE have become trapped, inducing the genesis of a new wide triangular-shaped beach on the updrift side (NW) of the harbor breakwall. This process induced a significant shoreline retreat of the south-east sector of the littoral. Widespread beach erosion of the coastal physiographic unit of Castellammare di Stabia Gulf (delimited by two ports) is more developed in the southern portion. This study highlights a slight rotation of the shoreline toward the East and a general trend of regression, with typical overall accentuation of shoreline concavity, and significant widening of the triangular-shaped beaches at the end of the falcate. This reduced sediment input removed from the sedimentary budget a large amount of deposits, which are hardly restorable due to the scarce supply of sediment load by the Sarno and its tributaries. In addition to this new and important derived morphologic feature, other recent human interventions have contributed to further modifications of morphologic characteristics of emerged and submerged beach. The intense use of the territory caused modifications on both the fluvial course and river mouth with direct and indirect effects on the shoreline and the drainage network of the Sarno River.

Keywords: coastal geomorphology; longshore ; historical maps; Gulf of Castellammare di Stabia; Gulf of Napoli

1. Introduction Longshore sediment transport is important on most of the coastline; the direction of the net longshore sediment transport of the coastline may be manifested from natural features and by the accumulation of sediment behind obstacles such as harbors, breakwalls and . Interference with the natural longshore sediment transport is caused by human-induced problems. It has been largely demonstrated that human impact and port construction can significantly modify the pattern of sediment transport, promoting dramatic changes in coastline evolution and longshore sediment budget ([1–4]; among others).

Geosciences 2018, 8, 235; doi:10.3390/geosciences8070235 www.mdpi.com/journal/geosciences Geosciences 2018, 8, 235 2 of 19 Geosciences 2018, 8, x FOR PEER REVIEW 2 of 19

Morphosedimentary analysis, coastline changes, long-term reconstruction of progradational and erosion processes and sediment budget estima estimationtion represent the key data to investigate the human-induced modificationmodification of coastal areas and to constrainconstrain sedimentsediment transporttransport modeling.modeling. In thisthis paper,paper, a detaileda detailed geomorphological geomorphological and and sedimentary sedimentary study study of a coastal of a coastal area largely area affectedlargely affectedby human-induced by human-induced alteration alteration of the coastline of the coas andtline longshore and longshore sediment sediment budget. Thebudget. coastal The sector coastal of sectorCastellammare of Castellammare di Stabia di Gulf Stabia is the Gulf minor is the physiographic minor physiographic unit of the unit main of the one main located one located in the Napoli in the NapoliGulf (Figure Gulf 1(Figure). 1).

Figure 1. Geological map of Gulf of Napoli, southern Italy (after [5], mod). Inset shows a Figure 1. Geological map of Gulf of Napoli, southern Italy (after [5], mod). Inset shows a geographical geographical sketch of southern Italy (the study area is shown in the circle). sketch of southern Italy (the study area is shown in the circle).

It consists of a narrow sandy beach, surrounded by the artificial harbors of Torre Annunziata to the NorthwestIt consists and of a Castellammare narrow sandy beach,di Stabia surrounded to the Southeast by the (Figure artificial 2), harbors and cut ofin Torrethe middle Annunziata by the Sarnoto the NorthwestRiver mouth. and The Castellammare presence of artificial di Stabia harb to theors Southeastlocated at (Figurethe extremes2), and of cut the in units the middle implies by a differentthe Sarno transport River mouth. by wave-generated The presence of artificiallongshore harbors currents, located which at thecauses extremes a weak of the rotation units impliesof the shorelinea different towards transport the by East, wave-generated linked to an overall longshore erosion currents, on the which downdrift causes side a weak of the rotation sandy beach, of the thatshoreline is more towards evident the on East,its Southern linked tosector. an overall Theref erosionore, the changes on the downdrift carried out side by human of the sandy activities beach, on thethat coastal is more system evident are on studied its Southern with sector.the same Therefore, methods the used changes for the carried investigation out by human of other activities coastal areason the [6–15]. coastal system are studied with the same methods used for the investigation of other coastal areasHuman [6–15]. activities and coastal engineering works cause both direct and indirect transformations on coastal processes, having an environmental impact on the coastal system [16–20]. Therefore, these

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HumanGeosciences activities2018, 8, x FOR and PEER coastal REVIEW engineering works cause both direct and indirect transformations3 of 19 on coastal processes, having an environmental impact on the coastal system [16–20]. Therefore, theseactivities activities and and their their effects effects must must be analyzed be analyzed before before their origin, their origin, even outside even outsidethe physiographic the physiographic unit in question, to define the coastal morphoevolution tendency. unit in question, to define the coastal morphoevolution tendency. Our results allowed identification of the critical area where appropriate actions can be Our results allowed identification of the critical area where appropriate actions can be developed developed for the mitigation of impacts and can represent a basic contribution to the coastal zone for themanagement. mitigation of impacts and can represent a basic contribution to the coastal zone management.

Figure 2. Location, map, and main toponyms of Castellammare di Stabia gulf. Figure 2. Location, map, and main toponyms of Castellammare di Stabia gulf. 2. Methods 2. Methods Reconstruction of the historical morphosedimentary evolution of the study area has been Reconstructioncarried out through of an the integrated historical geomorphologic morphosedimentaryal and sedimentological evolution of theanalysis study supported area has by been carriedmeteomarine out through data an and integrated morphobathymetic geomorphological surveys. Classical and sedimentological analysis of the shoreline analysis supportedevolution by meteomarinebased on multitemporal data and morphobathymetic analysis of aerial photogrammetry surveys. Classical and analysis topographic of themaps shoreline has been evolution also basedintegrated on multitemporal using historical analysis maps of(years aerial 1867 photogrammetry and 1906), which and furnished topographic relevant—although maps has been qualitative—information about the geomorphological features of the ancient coastal landscape. also integrated using historical maps (years 1867 and 1906), which furnished relevant—although More specifically, analysis of the coastline evolution based on the comparison of topographic maps qualitative—information(years 1865, 1906, 1941 and about 2000) the and geomorphological ortophoto (year 2018) features has been of integrated the ancient with coastalthe geological, landscape. Moregeomorphological, specifically, analysis and ofsedimentological the coastline evolutiondata to infer based the prograding on the comparison and eroding of topographic sectors of the maps (yearsstudy 1865, area. 1906, 1941 and 2000) and ortophoto (year 2018) has been integrated with the geological, geomorphological,Detailed analysis and sedimentologicalof geomorphological data and tosedimentological infer the prograding features of and the erodingGulf of Napoli sectors and of the studyCastellamare area. di Stabia gulf is based on a large amount of data collected during topographic and Detailedbathymetric analysis surveys of and geomorphological sediment sampling and along sedimentological emerged and submerged features beach. of the Gulf of Napoli and CastellamareThe sedimentary di Stabia gulf morphodynamics is based on a along large the amount coast of of the data Castellammare collected during di Stabia topographic Gulf was and bathymetricdeduced surveys from the andanalysis sediment of sedime samplingnt transportation along emerged vectors andalong submerged the entire coastline, beach. based on the study of the modal analysis of each sediment sample and their appearance frequency [21,22]. This The sedimentary morphodynamics along the coast of the Castellammare di Stabia Gulf was analysis allows identification of the grain size fractions involved in the sedimentary dynamics of the deducedphysiographic from the unit analysis of interest. of sediment transportation vectors along the entire coastline, based on the studyThe of thesedimentological modal analysis study of of each the physiographic sediment sample unit (Castellammare and their appearance di Stabia frequencyGulf) is based [21 ,22]. This analysison the grain allows size identificationanalysis of 40 ofsamples the grain of bottom size fractions sediment involved and on 12 in samples the sedimentary of emerged dynamics beach of the physiographic unit of interest. The sedimentological study of the physiographic unit (Castellammare di Stabia Gulf) is based on the grain size analysis of 40 samples of bottom sediment and on 12 samples of emerged beach Geosciences 2018, 8, 235 4 of 19 sediment [23]. The analysis, carried out with sieving and pipetting, allowed obtaining of the grain size composition and statistical parameters of [24]. Moreover, meteomarine climate has been inferred by a previous study of the direction and intensity of the main climate events of the coast [25]. The study is based on the analysis of the main wind direction using data from the Ponza Island oceanographic buoy (period 1989–2003). All the above-mentioned information has been used to infer the long-term morphosedimentary evolution of the coast and the effect of human activities on the coastal morphoevolution and sediment transport. These results have been summarized in a map of sediment transportation vectors, which represent a basic contribution to the long-term evaluation of effect of the Torre Annunziata harbor construction on the longshore processes of sediment transport.

3. Geological and Geomorphological Setting The beach in the Castellammare di Stabia Gulf borders seawards the Sarno River alluvial plain (southern Italy) (Figure1). The geomorphological evolution of the plain conditioned the physiography of the coast, on which the effects of the human activities have been superimposed. The coastal plain of the Sarno River represents the emerged portion of a morphotectonic depression bounded by carbonate morphostructures (Figure1), originated between the end of the Pliocene and the beginning of the Pleistocene [26,27]. It was filled by successions of alluvial, volcanoclastic, marine and deposits reworked in different quantity by the widespread runoff of surface waters and gravitational phenomena [28–30]. The plain expands for about 200 square kilometers, from the harbor of Torre Annunziata to that of Castellammare di Stabia, extending for about 13 kilometers in length. It is delimited to the north by Somma-Vesuvio volcanic complex, eastward by the Sarno massif, southward by carbonate highs of the Peninsula and westward by the Gulf of Napoli (Figure1). The slopes are covered by volcanoclastics alternating with detritic limestone and disturbed pyroclastics [31]. The widespread presence of tuff, lapilli, scoria and ash is mainly due to intense explosive activity of the Somma-Vesuvius [32] and the Phlegrean Fields [33] volcanoes. The present-day morphology of the study area is largely controlled by the complex interaction between tectonic and volcano-tectonic movements, sea-level rises promoted by long- and short-term climate changes and human impacts. Previous work highlights the predominant role of volcanic activity as the main endogenic controlling factors of the Holocene coastal evolution [5]. Historical seismic activity (earthquakes of AD 62 and AD 64 [30]) is older than the AD 79 eruption and the crustal deformations are presumably caused by the inflation of magma bodies underneath the Somma-Vesuvius volcanic complex [30]. The Vesuvian coast has been strongly modified by the effects of the Plinian eruption of Vesuvius in AD 79 (Aucelli et al., 2017). In the Sarno coastal plain a subsiding trend, partially due to regional tectonics and the compaction of loose sediments, was compensated by substantial clastic contributions related to the emplacement and reworking of pyroclastic products of the Vesuvius volcano [5]. Along the coast, there are rare traces of paleoshorelines [30] and , partially obliterated, while present dunes are completely absent. The latter has been completely leveled and urbanized with the construction of industrial complexes and houses. The Sarno River is a resurgent river and its solid contribution has always been relatively modest, the exception being the periods of volcanic activity. It originates from the Palazzo, Santa Marina and Cerola springs; two other springs—the San Mauro and the Santa Marina di Lavorate—are practically exhausted due to the excessive uptake [34]. In the past, the river was characterized by a meandering path (Figure3). The morphostratigraphic study of some sedimentary successions has allowed the reconstruction of the trace of ancient meanders of the Sarno River during the Holocene age, located in the Northern portion of the plain [31], to the N of the current mouth. Geosciences 2018, 8, 235 5 of 19

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Figure 3. Schematic geomorphological map of Castellammare di Stabia coastal area. Legend: (1) Figure 3.alluvialSchematic fan deposits geomorphological in piedmont areas map (Holocen of Castellammaree); (2) Sarno paleo-riverb di Stabiaed; coastal (3) sandy, area. gravelly Legend: (1) alluvialbeaches; fan deposits (4) sandy in beaches; piedmont (5) er areasosional (Holocene); beach; (6) progradational (2) Sarno paleo-riverbed; beach; (7) Sarno river’s (3) sandy, ancient gravelly beaches;mouth (4) sandy complex; beaches; (8) Sarno (5) river’s erosional current beach; mouth (6) complex; progradational (9) channel beach; incised (7)in the Sarno bottom; river’s (10) ancient mouth complex;isobaths (1 m (8) interval); Sarno (11) river’s detached current submerged mouth br complex;eakwaters; (12) (9) Recent channel coastal incised engineering in the works. bottom; (10) isobaths (1 m interval); (11) detached submerged breakwaters; (12) Recent coastal engineering works. 4. Geomorphological Features of the Coastal Area

4. GeomorphologicalThe coastal area Features we studied of the has Coastal a NW-SE Area orientation and it is cut in the middle by the Sarno River (Figures 2 and 3). The beach is sandy, and it has superficial accumulations of flattened gravels. TheThe coastal gravels, area reworked we studied by the sea has action, a NW-SE are likely orientation linked to a anddejection it is phase cut in of thethe Sarno middle River by and the Sarno River (Figuresof its streams2 and 3(-S.). The beach Marco is sandy, and Calcarella). and it has This superficial process was accumulations studied in the of Sarno flattened coastal gravels. The gravels,plain reworkedand it is verified by the during sea action, the maximum are likely marine linked ingr toession a dejection related phase to the ofHolocene the Sarno sea-level River and of highstand (5.8 ky BP). its streams (Gragnano-S. Marco and Calcarella). This process was studied in the Sarno coastal plain At present the beach is eroding overall (Figure 3), reaching a width that ranges from 15 to 30 m, and it isexcept verified for two during triangular-shaped the maximum sect marineors in progradation ingression at related the extremities, to the Holocene adjacent to sea-level the harbor’s highstand (5.8 ky BP). At present the beach is eroding overall (Figure3), reaching a width that ranges from 15 to 30 m, except for two triangular-shaped sectors in progradation at the extremities, adjacent to the harbor’s inner breakwaters of Torre Annunziata (wide beach of up to 200 m) and of Castellammare di Stabia (wide beach of up to 150 m). The sand towards the North is predominantly of volcanic origin and of dark gray color. Gradually, starting from the intermediate stretch, it becomes carbonate, assuming S Geosciences 2018, 8, 235 6 of 19 shades that are always clearer than gray. Its nature is to be ascribed to the lithology of the geological complexes that are present at the boundaries of the physiographic unit. The submerged morphology of the study area (Figure3) has been reconstructed from the analysis of bathymetric surveys using a single beam echo sounder [23]. It appears to be regular and characterized by weak gradients of inclination, on average equal to 2% for the interval between the shoreline and the bathymetric of 20 m placed at about 1000 m from the shoreline. The passes gradually from medium sand near the coast to fine sand up to transition offshore (see paragraph Morphodynamic of sediments). In the central sector of the study area, there is a fine sandy accumulation related to the current Sarno River mouth complex, which extends beyond the bathymetric of −20 m. In front of the sea, between the 5 m and 10 m bathymetrics, there is the limestone Rovigliano islet, which constitutes the morphological expression on the surface of the structural high of the Monti di Sarno [35]. There are also evidences of ancient mouth complexes of the Sarno River (Figure3) that extend up to 7 m of depth, characterized by the gradual change in grain size of sediments from fine sandy, near the coast, to very fine sandy offshore, and to strips of ancient depositional elements related to river mouths flowing into the Southern portion of the gulf, partly obliterated by both the coastal defense works and the Castellammare di Stabia harbor. Just North of the Sarno River mouth, there are ancient accumulations of mouth complex at the Holocene river plan (Figure3). Only in front of this stretch, the emerged beach is made up of gravelly deposits with rounded pebbles of about 10 cm average diameter, mainly of volcanic origin. The identification of these deposits at sea and on land allows confirmation of the presence in this sector of an ancient thalweg of the Sarno River, which probably dated back to the Holocene. To complicate this morphological structure even further, accumulations of sediments or channels incised in the bottom (Figure3) are evident as a response to the development of coastal defense works or harbor structures. In particular, at the mouth of the Torre Annunziata and Castellammare di Stabia harbors, there are areas with sediment accumulations, while, at the mouth of the Marina di Stabia touristic harbor (Figure2), there is a deep channel incised at the bottom. In the Southern sector of the gulf, in front of some detached breakwaters that were placed seaward of the shoreline approximately in the year 2000, the seabed is shallow, particularly in the areas that are in between the coastal-protection structure and the shoreline. In this area, there is also a tendency to progradation of the beach, which is made evident by the 1 m bathymetric trend, especially in the Southern portion. At the end of these structures, there are incised channels in the bottom that can be associated with the evacuation of sea water.

5. Influence of Human Activities on the Coastal Morphoevolution

5.1. Historical Activities The comparison of historical topographic maps of the area (e.g., [18]) allows detection of the genesis and the morphoevolution of a new beach North of the Torre Annunziata harbor, outside of the analyzed physiographic unit and the field identification of longshore sediment transport [36–40]. In particular, in a topographic and bathymetric map of 1865 with a 1:25,000 scale (Figure4), which was used as topographic base with an early reference the railway station (that was also used for all subsequent maps), the harbor of Torre Annunciata (today Torre Annunziata) was still not present. A large natural beach is also visible on the map, the Salera, the “Mezza Chiaia” and “La Chiaia” (Figure5A), a large structure associated with the Sarno River mouth located around the present one, with a large sandy bar to the right site of the mouth, beyond a natural meandering river. In the bottom part of the map, the Castellammare di Stabia harbor is evident, built in 1723, along with the Northern sector of Monti Lattari of the with its waterways (Rivi) at their natural state flowing into the Gulf of Castellammare di Stabia. At present, Rivi and Sarno are regimated and tombed. Historical reports show that the construction of Torre Annunziata harbor started in Geosciences 2018, 8, 235 7 of 19 Geosciences 2018, 8, x FOR PEER REVIEW 7 of 19

Geosciences 2018, 8, x FOR PEER REVIEW 7 of 19 1867regimated and was completedand tombed. in Historical 1871; the reports new harborshow that rested the construction on a modest ofpromontory Torre Annunziata called harbor La Storta started in 1867 and was completed in 1871; the new harbor rested on a modest promontory called La (Figuresregimated5A and 6and), which tombed. is Historical made up reports of Vesuvian show that lithic the volcanic construction deposits of Torre of theAnnunziata debris flow harbor type. Storta (Figures 5A and 6), which is made up of Vesuvian lithic volcanic deposits of the debris flow A historicalstarted IGMin 1867 map and which was completed dates to 1906in 1871; (Figures the new5B harbor and6 )rested shows on the a modest Torre Annunziatapromontory called harbor La for type.Storta A (Figures historical 5A IGM and map6), which which is datesmade toup 1906 of Vesuvian (Figures lithic5B and volcanic 6) shows deposits the Torre of the Annunziata debris flow the first time. In this map, a new narrow beach is evident to the NW of the artificial harbor, between harbortype. Afor historical the first IGMtime. map In this which map, dates a new to 1906narro (Fwigures beach 5B is andevident 6) shows to the the NW Torre of the Annunziata artificial the “Laharbor,harbor Storta” betweenfor headlandthe firstthe “Latime. and Storta” In the this harbor. headland map, a andnew the narro harbor.w beach is evident to the NW of the artificial harbor, between the “La Storta” headland and the harbor.

Figure 4. Historical map (year 1865) at a 1:25,000 scale. Please note that the Torre Annunciata harbor Figure 4. Historical map (year 1865) at a 1:25,000 scale. Please note that the Torre Annunciata harbor (todayFigure Torre 4. Historical Annunziata) map (yearis not 1865)present at ain 1:25,000 the map. scale. Please note that the Torre Annunciata harbor (today Torre Annunziata) is not present in the map. (today Torre Annunziata) is not present in the map.

Figure 5. Torre Annunziata coastal area morphoevolution from 1865 to 2018. (A) 1865 map: the harborFigure of 5. Torre Torre Annunziata Annunziata was coastal not shownarea morphoevolution on maps yet. The from red 1865arrows to indicate2018. (A the) 1865 direction map: theof Figure 5. Torre Annunziata coastal area morphoevolution from 1865 to 2018. (A) 1865 map: the harbor longshoreharbor of currents;Torre Annunziata the green wasarrow not indi showncates on a promontorymaps yet. The called red Laarrows Storta; indicate (B) a historicalthe direction IGM of of Torre Annunziata was not shown on maps yet. The red arrows indicate the direction of longshore maplongshore from 1906currents; shows the the green Torre arrow Annunziata indicates harbor a promontory for the firstcalled time. La Storta;Gradually, (B) a thehistorical sediments IGM currents;carriedmap the from by green NW-SE 1906 arrow shows longshore indicates the currentsTorre a promontoryAnnunziata became trapped. harbor called A Lafor new Storta;the narrow first (B time.) beach a historical Gradually, is evident IGM theto mapthe sediments NW from of 1906 showsthecarried the artificial Torre by NW-SE Annunziataharbor; longshore (C) 2018: harbor currents a wide for became thetriangular-shaped first trapped. time. Gradually,A newbeac narrowh on thethe beach sedimentsupdrift is evident side carried (NW) to the byofNW the NW-SE of longshorebreakwallthe artificial currents of theharbor; became Torre ( CAnnunziata trapped.) 2018: a Awide harbor. new triangular-shaped narrow The red beach curved is evidentbeacarrowsh on indicate to the the updrift NW the ofeffect side the of artificial(NW) the waveof harbor;the (C) 2018:diffractionbreakwall a wide processesof triangular-shapedthe Torre around Annunziata both the beach harbor. outer on breaThe the kwatersred updrift curved of side thearrows (NW)Torre indicate Annunziata of the the breakwall effect harbor of the ofand thewave the Torre Annunziataouterdiffraction jetty harbor. ofprocesses the The Apreamare red around curved bothboatyard. arrows the outer These indicate brea proc thekwatersesses effect have of of the theled Torre waveto the Annunziata diffractiongradual growth harbor processes ofand new aroundthe triangular-shaped beaches in down drift sides. both theouter outer jetty breakwatersof the Apreamare of the boatyard. Torre Annunziata These processes harbor have and led the to the outer gradual jetty ofgrowth the Apreamareof new boatyard. triangular-shaped These processes beaches have inled down to thedrift gradual sides. growth of new triangular-shaped beaches in down drift sides. Geosciences 2018, 8, 235 8 of 19 Geosciences 2018, 8, x FOR PEER REVIEW 8 of 19

The outer harborharbor breakwaterbreakwater promotespromotes sedimentsediment depositiondeposition onon thethe updriftupdrift side.side. The gradual development ofof thisthis beach beach (Figure (Figure6) 6) is alreadyis already evident evident in subsequentin subsequent historical historical maps, maps, for examplefor example the onethe one dated dated 1941, 1941, and and it continues it continues to become to beco largerme larger until until 2018 2018 (Figures (Figures5C and 5C6 and). 6).

Figure 6. Shoreline evolution from 1865 to 2018. Legend: 1—1865 shoreline before the Torre Figure 6. Shoreline evolution from 1865 to 2018. Legend: 1—1865 shoreline before the Torre Annunziata Annunziata harbor was built; 2—1872/76 shoreline after the Torre Annunziata harbor was built; harbor was built; 2—1872/76 shoreline after the Torre Annunziata harbor was built; 3—1941 shoreline; 3—1941 shoreline; 4—2018 shoreline; 5—erosional beach; 6—progradational beach. 4—2018 shoreline; 5—erosional beach; 6—progradational beach. Recently, the Torre Annunziata harbor caused a radical modification in the natural The outer harbor breakwater promotes sediment deposition on the updrift side. The gradual morphological structure of the coastal zone located to the South, in the Gulf of Castellammare di development of this beach (Figure6) is already evident in subsequent historical maps, for example the Stabia, resulting into a general on the downdrift side (Figure 6). one dated 1941, and it continues to become larger until 2018 (Figures5C and6). The harbor, located at the Northern edge of the gulf, has strongly modified the longshore Recently, the Torre Annunziata harbor caused a radical modification in the natural morphological sediment transport processes, with direction from NW to SE; in fact it traps the sediments carried by structure of the coastal zone located to the South, in the Gulf of Castellammare di Stabia, resulting into the longshore currents, allowing them to be accumulated in a new wide beach (Figure 3 and 5C), a general coastal erosion on the downdrift side (Figure6). now about 200 m wide (Figure 7), in the updrift area on the North edge of the harbor. This new sandyThe beach, harbor, which located is about at the Northern150 years edge old, ofwas the built gulf, hasclose strongly to a high modified rocky the coast longshore formed sediment by lava transportdeposits and processes, it is affected with direction by progradational from NW to proce SE; insses fact of it approximately traps the sediments 1 m/yr. carried In fact, by theit constitutes longshore currents,the point allowingof final delivery them to of be the accumulated sediments intranspor a new wideted in beach the physiographic (Figures3 and unit5C), that now borders about 200 to mthe wideNorth (Figure the one7), in in object. the updrift area on the North edge of the harbor. This new sandy beach, which is aboutThe 150 continuous years old, was subtraction built close of todrifting a high sediment rocky coasts trapped formed by by Torre lava deposits Annunziata and itharbor is affected has led by progradationalto a marked coastal processes erosion of approximately in the Gulf of 1Castel m/yr.lammare In fact, itdi constitutes Stabia, located the point on the of finaldowndrift delivery side of the(Figure sediments 6). This transported has shaped in a thefirst physiographic new important unit mo thatrphological borders tostructure the North of thethis one coastline, in object. defined by a concave coast in erosion, surrounded by large beaches protected by the outer breakwater of the

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The continuous subtraction of drifting sediments trapped by Torre Annunziata harbor has led to a marked coastal erosion in the Gulf of Castellammare di Stabia, located on the downdrift side (Figure6). This has shaped a first new important morphological structure of this coastline, defined by a concaveGeosciences coast 2018, 8 in, x erosion,FOR PEER surrounded REVIEW by large beaches protected by the outer breakwater of the9 of Torre 19 Annunziata harbor to the North and by the Castellammare di Stabia harbor to the South. The harbor Torre Annunziata harbor to the North and by the Castellammare di Stabia harbor to the South. The structuresharbor structures also define also and define delimit and adelimit new physiographic a new physiographic unit. unit.

Figure 7. Panoramic view of the 200 m-wide new sandy beach of the Torre Annunziata showing a Figure 7. Panoramic view of the 200 m-wide new sandy beach of the Torre Annunziata showing a triangular shape. triangular shape. The reduced sedimentary input removed a strong amount of sediments from the sedimentary budgetThe reducedof the Gulf sedimentary of Castellammare input removed di Stabia a strong, no amountlonger replaceable of sediments due from to the sedimentarylow solid budgetcontribution of the Gulf of the of Sarno Castellammare River, the diresurgence Stabia, no river, longer its tributaries replaceable and due the to Rivi. the low solid contribution of the SarnoUltimately River, there the resurgence is a weak river,rotation its tributariesof the shor andeline the [41] Rivi. toward the East (Figure 6), to be associatedUltimately with there the isgeneral a weak tendency rotation to of shoreline the shoreline retreat [41 ]with toward a typical the East generalized (Figure6 ),accentuation to be associated of withthe the concavity general of tendency the shoreline, to shoreline more marked retreat within th ae typicalSouthern generalized portion and accentuation a strong progradation of the concavity of ofthe the beaches, shoreline, with more triangular marked morphology, in the Southern at the ends portion of the and gulf a (Figures strong progradation 3 and 6). These of wide the sandy beaches, withshores, triangular with a width morphology, of about at150 the m today, ends of located the gulf on the (Figures harbor3 innerand6 ).breakwaters These wide perpendicular sandy shores, to withthe a coast width (Figures of about 5C, 150 8 mand today, 9), have located accumulated on the harbor due to inner the waves breakwaters diffraction perpendicular process around to the the coast (Figuresharbors5C, outer8 and breakwaters.9), have accumulated The great duewidth to of the the waves beaches diffraction does not process allow their around periodic the harbors washing outer by the waves of the sea; this means that dust is accumulated causing the growth of grass. breakwaters. The great width of the beaches does not allow their periodic washing by the waves of the sea; this means that dust is accumulated causing the growth of grass.

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Figure 8. Shoreline response after the built up of coastal engineering works (the letters indicate the Figure 8. Shoreline response after the built up of coastal engineering works (the letters indicate the stretchesFigure 8. ofShoreline the beach response that are after under the progradation). built up of coas Legend:tal engineering (1) progradational works (the beaches; letters indicate (2) coastal the stretches of the beach that are under progradation). Legend: (1) progradational beaches; (2) coastal engineeringstretches of theworks; beach (3) thatdetach areed under submerged progradation). breakwaters. Legend: (1) progradational beaches; (2) coastal engineering works; (3) detached submerged breakwaters. engineering works; (3) detached submerged breakwaters.

Figure 9. Wide triangular-shaped sandy beach of Castellammare di Stabia with a maximum width of Figure 9. Wide triangular-shaped sandy beach of Castellammare di Stabia with a maximum width of Figureabout 150 9. Wide m. triangular-shaped sandy beach of Castellammare di Stabia with a maximum width of about 150 m. about 150 m. 5.2. Recent Activities 5.2. Recent Activities 5.2. RecentRecently Activities coastal engineering, including other human activities, have further conditioned the Recently coastal engineering, including other human activities, have further conditioned the new Recentlymorphological coastal setting. engineering, To the includingSouth of Torre other An humannunziata activities, harbor, have two further curved conditioned jetties, which the were new new morphological setting. To the South of Torre Annunziata harbor, two curved jetties, which were morphologicalbuilt in about 2005 setting. in defense To the Southof the ofApreamare Torre Annunziata boatyard harbor, (Figures two 2 curvedand 3), jetties,caused which the growth were builtof a sandybuilt in beach—due about 2005 ain waves defense diffraction of the Apreamare process—over boatyard 80 m (Figureswide (Figures 2 and 3,3), 5C caused and 8) the adjacent growth to of the a innersandy jetty beach—due of this stretch a waves of diffractionthe beach, process—overwhich was characterized 80 m wide (Figuresby a historical 3, 5C and tendency 8) adjacent to erosion to the beforeinner jetty the constructionof this stretch of ofthis the structures. beach, which was characterized by a historical tendency to erosion before the construction of this structures.

Geosciences 2018, 8, 235 11 of 19 in about 2005 in defense of the Apreamare boatyard (Figures2 and3), caused the growth of a sandy beach—dueGeosciences a 2018 waves, 8, x FOR diffraction PEER REVIEW process—over 80 m wide (Figures3,5C and8) adjacent to the11 of inner 19 jetty of this stretch of the beach, which was characterized by a historical tendency to erosion before the constructionMore of thisto the structures. South, in an almost central position, there is the Sarno River mouth, strongly stiffened by two jetties that protrude into the sea and by breakwaters built parallel to the shoreline More to the South, in an almost central position, there is the Sarno River mouth, strongly stiffened (Figure 8). They are static features in conflict with the dynamic beach changes and they impede the by two jetties that protrude into the sea and by breakwaters built parallel to the shoreline (Figure8). exchange of sediment between land and sea. In particular, to the North of the mouth, the shoreline They areretracted static about features 30 m in in conflict the period with 1968–1989, the dynamic due to beach the construction changes and of the they jetty impede by the theright exchange mouth. of sediment betweenSouth of the land Sarno and River sea. Inmouth, particular, there is to the the new North Marina of thedi Stabia mouth, touristic the shoreline harbor (built retracted in 2004) about 30 m inlocated the period in correspondence 1968–1989, dueof the to area the constructionalready affected of theby six jetty detached by the rightbreakwaters mouth. placed before South1956, due of the to generalized Sarno River erosive mouth, phenomena. there is the Also new in Marinathis case, di the Stabia waves touristic diffraction harbor process (built caused in 2004) locatedby in outer correspondence breakwaters of theof areathe touristic already affectedharbor bypromotes six detached sediments breakwaters deposition placed in beforea new 1956, due totriangular-shaped generalized erosive beach, phenomena. adjacent to Alsothe inner in this breakwater, case, the waveswith a diffractionmaximum width process of causedabout 80 by m outer breakwaters(Figuresof 3 and the 8). touristic harbor promotes sediments deposition in a new triangular-shaped beach, Finally, the outer breakwater of the Castellammare di Stabia harbor, which was extended first adjacent to the inner breakwater, with a maximum width of about 80 m (Figures3 and8). between 1936 and 1941 and later in 1970 and in 1990, has promoted sediments deposition due to Finally, the outer breakwater of the Castellammare di Stabia harbor, which was extended first waves diffraction process adjacent to the inner breakwater. As a result, a wide triangular-shaped betweensandy 1936 beach and with 1941 a andmaximum later inwidth 1970 of and about in 150 1990, m has been promoted progressively sediments generated deposition (Figures due 8 and to 9). waves diffractionThis beach process developed adjacent over to thethe innerold mouth breakwater. deposits Asof San a result, Pietro a stream. wide triangular-shaped In the submerged beach, sandy the beach with amouth maximum complex width partially of about dismantled 150 m hasby a been series progressively of detached submerged generated breakwaters (Figures8 and is visible.9). This beach developedThese over breakwaters the old mouth that depositswere placed of Sanin about Pietro 2000 stream. at a depth In the of 3–5 submerged m, consist beach, of 9 boulders the mouth complexelements partially (Figure dismantled 3), aimed by at acontaining series of detachedongoing erosion submerged processes breakwaters that were threatening is visible. the road Thesesystem breakwaters of Castellammare that weredi Stabia placed town. in aboutFurthermore, 2000 at the a deptherosion of had 3–5 partially m, consist uncovered of 9 boulders the elementsfoundations (Figure 3of), a aimed hotel structure at containing on the ongoing beach (ex erosion Hotel Miramare, processes Figure that were 10A,B). threatening As the original the road breakwaters were not providing an effective protection, after about ten years, these were reinforced system of Castellammare di Stabia town. Furthermore, the erosion had partially uncovered the to include up to twelve elements. The subsequent morphological surveys up to 2018 have allowed foundationsverification of a of hotel a weak structure trend towards on the beachthe progra (exdation Hotel Miramare,of the beach, Figure now about10A,B). 20 Asm width, the original in breakwatersaddition were to a substantial not providing recovery an effectiveof the beach protection, profile (Figure after 10C). about ten years, these were reinforced to includeFinally, up to twelvethe buildings, elements. walls, The artefacts, subsequent and fences morphological on the back of surveys the beaches up to strongly 2018 have limit allowed the verificationnatural of expansion a weak trend of the towards beach towa therds progradation the inner part, of giving the beach, the beac nowh an about unusual 20 m profile width, with in additionhigh to a substantialgradients and recovery sand accumulation of the beach near profile the structures. (Figure 10 C).

FigureFigure 10.10. RecentRecent evolution evolution of the of thebeach beach of the of Miramare the Miramare hotel. (A hotel.,B) the (erosionA,B) the processes erosion had processes partially had uncovered the foundations of the hotel structure. (C) weak progradation of the beach, now about 20 m partially uncovered the foundations of the hotel structure. (C) weak progradation of the beach, now wide. about 20 m wide.

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Finally, the buildings, walls, artefacts, and fences on the back of the beaches strongly limit the natural expansion of the beach towards the inner part, giving the beach an unusual profile with high gradients and sand accumulation near the structures.

6. Morphodynamic of Sediments The sedimentological study of the physiographic unit (Castellammare di Stabia Gulf) is based on the grain size analysis of 40 samples of bottom sediment and on 12 samples of emerged beach sediment [23]. The analyses, carried out with sieving and pipetting, allowed obtaining of the grain size composition and statistical parameters of [24]. The results are summarized in Table1.

Table 1. Sediment samples collected along the shoreline and at the sea bottom Castellammare di Stabia gulf. Grain-size data and statistical parameters of the beach and marine sediments according to the

graphic method of Folk and Ward (1957): Mz, mean size; σ, sorting; SKI, skewness; KG, kurtosis, and related textural group. Depths are expressed in meters and they refer to current mean sea level.

Sample Depth (m) Gravel Sand Mud Mz σ KG SKI Classification 10 0 0 100 0 2.19 0.42 1.09 –0.07 fine sand 11 0 0 100 0 2.23 0.39 1.08 –0.04 fine sand 36 0 0 99.97 0.03 2.32 0.42 1.11 –0.08 fine sand 90 0 0 99.99 0.01 1.5 0.49 1.11 0.02 medium sand 93 0 3.9 96.1 0 –0.35 0.33 1.05 –0.05 very coarse sand 95 0 29 99.71 0 0.66 0.38 1.26 –0.01 coarse sand 96 0 0 100 0 –0.02 0.33 1.05 0.08 very coarse sand 97 0 0.7 99.28 0.02 0.53 0.71 1.43 0.24 coarse sand 98 0 0 99.95 0.05 2.04 0.48 1.25 –0.04 fine sand 99 0 0.18 99.82 0 1.65 0.71 0.86 –0.15 medium sand 100 0 10.99 88.54 0.47 1.23 1.69 0.72 –0.15 medium sand 179 –5 0 93.46 6.54 2.67 0.25 –1.19 0.77 fine sand 180 –6.5 0 93.79 6.21 2.65 0.27 –1.23 –0.2 fine sand 181 –7.9 0 65.05 34.95 2.99 0.79 2.14 –0.3 fine sand 182 –9.5 0 94.95 5.05 2.6 0.44 6.68 –0.29 fine sand 183 –12.5 0 100 0 2.35 0.55 13.01 –0.08 fine sand 184 –15 0 93.6 6.4 2.45 0.7 0.87 0.09 fine sand 185 –4 0 99.81 0.19 1.38 0.42 1.25 –0.22 medium sand 186 –7 0 99.07 0.93 1.57 0.42 22.02 0.41 medium sand 187 –8.5 0 81.24 18.76 2.9 0.85 0.67 0.11 fine sand 188 –11 0 67.8 32.2 3.17 0.68 1.21 0.26 very fine sand 189 –14 0 67.42 32.58 3.37 0.64 1.36 0.71 very fine sand 190 0 0.11 99.87 0.02 1.45 0.65 0.89 0 medium sand 191 0 0.51 99.44 0.04 0.45 0.74 0.77 0.45 coarse sand 192 –1 0 99.95 0.05 1.35 0.35 1.52 1.94 medium sand 193 –3 0 93.66 6.34 2.62 0.6 1.48 –0.21 fine sand 194 –5.1 0 90.01 9.99 2.66 0.88 1.29 0.35 fine sand 195 –10 0 70.26 29.74 3.03 0.96 0.85 0 very fine sand 196 0 0 93.88 6.12 2.29 0.74 1.23 0.5 fine sand 197 –18.7 0 63.04 36.96 3.45 0.68 3.92 0.26 very fine sand 198 –1.2 0 81.17 18.83 3.15 0.52 1.2 –0.39 very fine sand 199 –4 0 79.58 20.42 2.96 0.8 0.82 –0.5 fine sand 200 –6 0 51.12 48.88 3.2 0.99 1.11 –0.49 very fine sand 201 –9.5 0 77.89 22.11 3.02 0.93 1.4 0.4 very fine sand 202 –12 0 86.03 13.97 2.56 0.95 1.55 0.06 fine sand 203 –13.9 0 77.65 22.35 3.06 0.88 0.76 –0.28 very fine sand 204 –16 0 78.42 21.58 2.79 1.05 0.76 –0.21 fine sand 205 0 1.15 98.85 0 0.51 0.83 0.83 0.54 coarse sand 206 –1 0.02 99.94 0.04 1.59 0.71 0.85 0.05 medium sand 207 –5.1 0 88.91 11.09 2.92 0.43 20.66 1.12 fine sand 208 –10.2 0 92.03 7.97 2.72 0.52 –14.23 –0.74 fine sand 209 –17.2 0 94.51 5.49 2.81 0.37 –2.16 0.89 fine sand 210 0 0.16 99.82 0.02 1.44 0.66 0.95 0.03 medium sand 211 –1 1.96 97.36 0.68 1.44 1.21 0.63 –0.49 medium sand 212 –6.8 0 93.81 6.19 2.18 1.14 0.67 –0.44 fine sand 214 –19 0 91.02 8.98 2.8 0.75 2.55 0.46 fine sand 215 –1 0 99.13 0.87 2.07 0.14 –0.56 0.19 fine sand 216 –4.8 0 95.44 4.56 2.37 0.64 16.12 –0.35 fine sand 217 –11 0 88.2 11.8 2.92 0.51 3.7 0.03 fine sand 218 –16.4 0 80.87 19.13 2.98 0.39 1.07 –2.64 fine sand 219 –18.7 0 85.16 14.84 2.81 0.88 1.15 –0.31 fine sand Geosciences 20182018,, 88,, 235x FOR PEER REVIEW 13 of 19

The sampling station location is shown in Figure 11, while the areal distribution of the mean grainThe size sampling (Mz), up station to a location depth isof shown20 m, inis Figure shown 11 ,in while Figure the areal12. All distribution the maps of are the meancreated grain on sizegeo-referenced (Mz), up to bathymetric a depth of 20 map m, is with shown geograph in Figureic 12coordinates. All the maps according are created to the on geo-referencedWGS 84 UTM bathymetricSystem. map with geographic coordinates according to the WGS 84 UTM System.

Figure 11. Location of sampling sites; isobaths: 1 m interval. Figure 11. Location of sampling sites; isobaths: 1 m interval.

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Figure 12. Grain size features of sediments and zonation within a 20 m depth. Figure 12. Grain size features of sediments and zonation within a 20 m depth.

Therefore, for the physiographic unit stretch placed to the North of the studied area, it has been foundTherefore, that the grain for the size physiographic fractions that unit most stretch effectively placed tocontribute the North to ofthe the sedimentary studied area, dynamics it has been of foundthe area that consist the grain of 25% size coarse fractions sand that(0.89–0.56 most effectivelymm grain size contribute range), toof the45% sedimentary medium sand dynamics (grain size of thebetween area consist0.43 and of 25%0.25 coarsemm) and sand fine (0.89–0.56 sand (0.24–0.14 mm grain range). size range), Instead of 45%in the medium physiographic sand (grain unit size of betweeninterest, the 0.43 grain and 0.25size mm)fractions and consist fine sand of (0.24–0.1410.29% very range). coarse Instead sand (range in the between physiographic 1.67 and unit 1.07 of interest,mm), of the23.53% grain coarse size fractions sand (range consist between of 10.29% 0.9 veryand 0.51 coarse mm), sand of (range 16.18% between medium 1.67 sand and (grain 1.07 mm), size ofrange 23.53% between coarse 0.43 sand and (range0.25 mm) between and of 0.938.24% and fine 0.51 sa mm),nd (grain of 16.18% size range medium between sand 0.24 (grain and 0.13 size mm). range betweenThese 0.43 results and 0.25 were mm) used and to of plot 38.24% the finesedimentar sand (grainy transit size rangeaxes maps between along 0.24 the and entire 0.13 mm).coastline (FigureThese 13). results The longshore were used currents to plot movement the sedimentary of the transitthree subpopulations axes maps along in thethe entireareas coastlinenear the (Figurecoast, within 13). The the longshore 10 m bathymetric, currents movementappears to ofbe, the overall, three from subpopulations NW to SE, inboth the in areas the physiographic near the coast, withinunit to thethe 10 North m bathymetric, of Torre Annunziata appears to be,harbor overall, and from in the NW physiographic to SE, both in unit the physiographicof Castellammare unit todi theStabia North Gulf. of Torre Annunziata harbor and in the physiographic unit of Castellammare di Stabia Gulf.

Geosciences 2018, 8, 235 15 of 19 Geosciences 2018, 8, x FOR PEER REVIEW 15 of 19

Figure 13. Vector axes of the main direction of sediment transport along the Gulf of Napoli and Figure 13. Vector axes of the main direction of sediment transport along the Gulf of Napoli and Castellammare di Stabia coast. Castellammare di Stabia coast. Therefore, also the results of such analyses allowed confirmation of the sediment transport modelTherefore, we identified also the thanks results to ofhistorical such analyses maps analysis. allowed confirmation of the sediment transport model we identifiedFinally, the thanks data to of historical the main maps wind analysis. direction and the main climate events were acquired from the [25].Finally, The the resulting data of vector the main of the wind offshore direction energy and theflows main is oriented climate eventsin the weredirection acquired 258.29° from N ◦ (Figurethe [25]. 14). The The resulting resulting vector directions of the of offshore the wave energy energy flows flows is orientednear the incoast the are: direction North 258.29 of SarnoN (FigureRiver 247.06° 14). The N, resulting near the directionsmouth of ofthe the river wave 254. energy44° N flowsand South near theof Sarno coast are:River North 262.90° of Sarno N. Having River ◦ ◦ ◦ verified247.06 N,the near NW–SE the mouthorientation of the of river the coastal 254.44 stretch,N andSouth it has ofbeen Sarno inferred River that 262.90 the N.incidence Having of verified wave approachthe NW–SE on orientation the coast is of mainly the coastal orthogonal. stretch, The it has resu beenlts inferredof these simulations that the incidence allowed of waveus to believe approach in theon thegenesis coast of is mainlya longshore orthogonal. current The going results South, of thesedue to simulations main climate allowed events us generated to believe incurrent the genesis from about the 260° N direction.

Geosciences 2018, 8, 235 16 of 19 of a longshore current going South, due to main climate events generated current from about the 260◦ Geosciences 2018, 8, x FOR PEER REVIEW 16 of 19 N direction.

Figure 14. Results of hydrodynamics and wave patterns (from [[25]).25]).

7. Conclusions Morphological research, analysis of historical maps and analysisanalysis ofof sedimentologicalsedimentological characteristics of bottom sediments carried out along the area on Neapolitan coast enabled to definedefine thethe processesprocesses and and their their evolution evolution in time in time and space.and sp Theace. results The ofresults this study of this have study allowed have verification allowed thatverification the predominant that the predominant longshore current longshore direction current and sedimentsdirection and transport sediments along transport the coast ofalong Napoli the Gulfcoast (southernof Napoli Italy) Gulf happens (southern from Italy) Northwest happens to fr Southeast.om Northwest Indeed, to theSoutheast. Torre Annunziata Indeed, the artificial Torre harborAnnunziata acts as artificial a dam to harbor littoral acts drift, as blockinga dam to the littoral sediment drift, movement blocking the along sediment the Neapolitan movement coast along and causingthe Neapolitan a significant coast shorelineand causing retreat a significant on the down-drift shoreline retreat side, which on the is down-drift in the coastal side, stretch which which is in extendsthe coastal from stretch Torre Annunziatawhich extends to Castellammare from Torre An dinunziata Stabia. Also, to Castellammare meteo-marine anddi anemometricStabia. Also, resultsmeteo-marine revealed and that anemometric the predominant results wave revealed direction that the from predominant W sector is responsiblewave direction for thefrom generation W sector ofis responsible longshore southward for the generation current. of longshore southward current. This work determined that the natural morphology of the coast of Castellammare di Stabia Gulf waswas intenselyintensely altered by the construction of the Torre AnnunziataAnnunziata harbor,harbor, whichwhich waswas completedcompleted in 1871.1871. The harbor was built near the northern edge of the Gulf,Gulf, intenselyintensely altering the sedimentarysedimentary morphodynamic of of the the nearby nearby phys physiographiciographic unit, unit, oriented oriented NW-SE. NW-SE. The The structure structure of the of harbor the harbor now nowtraps trapsthe sediments the sediments carried carried by bythe thelongshore longshore cu currents,rrents, causing causing deposition deposition North North of of the the outer breakwater area (on(on the updrift side of the structure)structure) and a genesis of a new beach which is currently growing. Consequently, the coastal system of the GulfGulf di CastellammareCastellammare located down drift side is now beingbeing intenselyintensely marked marked by by erosional erosional processes. processes. The The new new morphology morphology of theof the shoreline shoreline is made is made of a largeof a large arch arch currently currently eroded eroded and delimited and delimited at the at ends the byends wide by beacheswide beaches protected protected by breakwalls by breakwalls of two harbors:of two harbors: Torre Annunziata Torre Annunziata on the Northern on the side,Northe andrn Castellammare side, and Castellammare di Stabia on thedi SouthernStabia on side.the TheSouthern erosional side. processes The erosional are more processes intense are on more the South intense side on of the arch,South while side of the the triangular-shaped arch, while the beachestriangular-shaped developed graduallybeaches developed thanks to progressive gradually extensionthanks to of progressive the outer breakwaters. extension Lastly,of the it weakouter Eastwardbreakwaters. rotation Lastly, of it the weak shoreline Eastward related rotation to its retreatof the shoreline can be detected. related to its retreat can be detected. Further structures were built on this new morphology, causing further modifications of the emerged and submerged beaches. Between 2003 and 2006 new structures were built perpendicularly to the direction of the waves, causing the formation of new beaches, which are connected to the alteration of the beach drift. The morphology of the coast has also been altered by the construction of structures aimed at protecting the shoreline, draining channels, and seawalls. The area of the dunes

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Further structures were built on this new morphology, causing further modifications of the emerged and submerged beaches. Between 2003 and 2006 new structures were built perpendicularly to the direction of the waves, causing the formation of new beaches, which are connected to the alteration of the beach drift. The morphology of the coast has also been altered by the construction of structures aimed at protecting the shoreline, draining channels, and seawalls. The area of the dunes located on the back of the shores has been intensely modified, with the construction of industrial and residential complexes which block access to the beaches but also to the sediments supply. The human activity has also modified the morphology of the submerged beach, causing both deposition and erosion with the genesis of channels incising the bottom. The lower basin of the Sarno River and the overlooking shoreline have been intensely modified by human development, both agricultural and industrial, with alterations of the river bed, flow, banks, and the enclosure of its path in urban areas. This work on the morphological evolution of the coast of Castellammare di Stabia Gulf during an intense phase of human development shows that the latter clearly prevailed over the natural forces, and it highlights that, when examining a coastal area, it is of paramount importance to focus on the onset and the climax of local human development. Late phases of development are usually comparatively less relevant; however, they still need to be examined within the evolutional framework of the whole area. The study area represents an indicative example of a highly-urbanized coast in which human impact and the construction of a port have dramatically changed the long-term natural evolution and the longshore sediment distribution. Similar results have been obtained by scientists in different parts of the world [1,4,19,38,42,43] and suggest the crucial role of morphosedimentary data in plans.

Conflicts of Interest: The authors declare no conflict of interest.

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