Marine Pollution Bulletin 93 (2015) 183–193

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Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul

Assessing shelf aggregate environmental compatibility and suitability for beach nourishment: A case study for Tuscany (Italy) Nicola Bigongiari a,1, Luigi E. Cipriani b,1, Enzo Pranzini c,1, Monia Renzi d,1,⇑, Giovanni Vitale c,1 a

CIBM – Center of Marine Biology and Applied Ecology ‘‘G. Bacci’’, Viale N. Sauro 4, Livorno, Italy Region of Tuscany – D.G. for the Environment, Energy and Climate Change – Section for the Protection and Value Enhancement of Marine and Coastal Environments, via di Novoli, 26, 50127 Firenze, Italy c Department of Earth Sciences, University of Florence, Borgo Albizi 28, 50122 Firenze, Italy d Department of Biological and Environmental Sciences and Technologies, University of the Salento, SP Lecce-Monteroni, 73100 Lecce, Italy b

a r t i c l e

i n f o

Article history: Available online 13 February 2015 Keywords: Beach nourishment Nearshore Dry beach Pollution Sand compatibility

a b s t r a c t Beach nourishment practices are a key aspect in coastal management plans for stakeholders and communities. Stemming from a concrete case-study (Tuscany), this research analyzes: (i) principal problems of current law regulating dredging, (ii) gaps in technical guidelines, (iii) advantages of integrated approaches to the decision-making process, (iv) possible applicable nourishment options and their costs and benefits. Our results show that sand compatibility is driven mainly by grain-size stability due to the occurrence of lower pollution levels in off-shore deposits than in threatened beaches, thus current laws and guidelines should be improved to fill the evident gap in the evaluation process and to include a more complete approach to data evaluation and an integrated approach to ecotoxicity evaluation, which is relevant in cases of geochemical anomalies. The cost-benefit analysis performed indicates that only dredging intended to manage more than 1 million m3 of aggregates would represent a real advantage for local communities. Ó 2015 Elsevier Ltd. All rights reserved.

1. Introduction Coastal erosion affects approximately 100 km out of the total 200 km of continental sand beaches in Tuscany, with shoreline retreat values exceeding 10 m per year at specific sites (Cipriani et al., 2013). In order to stabilize these coastal sectors and maintain their environmental and economic value, some 2 million cubic meters of sediments are required each year (Danelon and Pranzini, 2013). Hard shore protection structures could reduce longshore and offshore sediment transport, reducing the amount of beach fill volume required, but this would increase downdrift erosion and reduce the resilience and economic value of the Tuscan coast. The Region of Tuscany opted for an intermediate solution, reducing the amount of hard protection (currently covering approximately 30 km of sand coast) and increasing soft shore protection by means of beach nourishment. Riverbed sediment quarrying has been prohibited in Tuscany since the 1970s, and the limited availability of aggregates in ⇑ Corresponding author. 1

E-mail address: [email protected] (M. Renzi). All authors contributed equally.

http://dx.doi.org/10.1016/j.marpolbul.2015.01.021 0025-326X/Ó 2015 Elsevier Ltd. All rights reserved.

regional alluvial plain quarries induced coastal restoration designers to look for sand in the Po River plain, with high environmental (CO2 emissions, noise, powder, traffic) and economic (€ 20–40 per m3) costs. In this scenario, the Region of Tuscany, as part of the Regional Plan for Integrated Coastal Zone Management (ICZM) in cooperation with local authorities (Provincial and Municipal Administrations) and River Basin Authorities, has coordinated and financed (with approximately € 110 million) a Programme for coastal restoration activities, beach evolution monitoring and the implementation of coastal studies (Sargentini et al., 2004). One important such study worthy of mention was a research project with the aim of searching for and characterizing sand and gravel deposits laying on the Tuscan continental shelf to be used for beach nourishment purposes. The study cost about € 2 million and allowed for the identification of four reservoirs as potential borrowing sites, with an estimated volume of approximately 129 million m3 of aggregates (Chiocci et al., 2009). Another part of the Regional ICZM Plan (€ 1 million invested) comprises the environmental characterization of continental shelf reservoirs, aimed at evaluating potential damage to marine and coastal environments resulting from sediment extraction, transport and deposition (Cipriani et al., 2011). Chemical, biological, ecotoxicological, sediment grain-size and

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colour data were used to assess the compatibility of these aggregates with the native sediments of beaches experiencing severe erosion in Tuscany. An especially important factor in this particular situation is the economic value of Italian beaches (from € 800/m2 to € 2500/m2 according to NOMISMA-www.beachmed.it), which generates strong local interest in managing the short-term evolution of the shoreline. The bottom-up decision-making process contrasts with the long-term and large-scale management of coastal sediments within physiographic units (Cappucci et al., 2011). Beach erosion is also a primary concern among summer tourists in the United States (Houston, 1995). The severe erosion of beaches determines a significant reduction in tourism, with adverse impacts on the local economy. Over the past few decades, the most popular approach to addressing beach erosion problems worldwide is to replace eroded sand with sand from the sea floor (Houston, 1996), a procedure on the increase in Europe as well (Pranzini and Williams, 2013). In addition, an evaluation of costs due to the effects of erosion in coastal areas resulting from climate change is crucial to the definition of adaptation strategies. Along Italian coasts, adaptation options to deal with the effects of climate change were first proposed by Cappucci in 2007 (BEACHMED, 2015). This analysis showed that defending the entire 4600 km of Italian sand coastline would not be economically sustainable. In fact, even if only the 1500 km of beaches that have already been subject to erosion were to be protected, a huge initial investment (about € 2 billion) would be necessary, along with repeated maintenance interventions over time. In this case, the amount of sediment required for beach nourishment was estimated at around 150–200 million m3 (approximately 100 m3 per meter of beaches), not to mention the quantities that would be necessary for maintenance interventions (BEACHMED, 2015). In Italy, beach nourishment using sand dredged from continental shelf reservoirs started in 1994 within the projects of coastal stabilization of the barrier islands protecting the Venice Lagoon; since then approximately 20 million m3 of aggregates have been extracted, mostly to nourish beaches in Veneto, Lazio and Emilia-Romagna (Pranzini, 2013). Many research programs are now comparing the availability (potential supply) of sand to carry out beach nourishment against the demand for sediments indicated by public authorities to contrast coastal erosion, but this analysis is still in progress (Correggiari et al., 2012). In addition, many environmental constraints specific to the Mediterranean Sea limit the possibility of reusing sediment for beneficial purposes (e.g. beach nourishment) if dredging is carried out along the coast or close to coastal infrastructures like harbours (Ausili et al., 2012; Cappucci et al., 2011; Lisi et al., 2009). The PESETA Project (Ciscar et al., 2014) used the Dynamic and Interactive Vulnerability Assessment (DIVA) model (Vafeidis et al., 2008; Hinkel and Klein, 2009) to estimate annual damage costs in 2020 and 2080 for two scenarios – low and high sea level rise (representing low and high climate sensitivity for the A2 SRES scenario, Nakicenovic et al., 2000). Total costs (i.e. damage and adaptation costs) were estimated first for a no-adaptation scenario, and second when adaptation (dike construction and beach nourishment) was taken into account. Total costs were found to be much higher without adaptation, thus adaptation was shown to be a highly cost-effective investment. Based on a concrete case study carried out in Tuscany, the aim of the present research is to evaluate the compatibility of continental shelf aggregates for the nourishment of Tuscan beaches, and also to perform a cost-benefit analysis related to possible future needs due to erosion processes linked to global climate change (IPCC, 2007).

2. Materials and methods 2.1. Sediment sampling Continental shelf sediments were collected in two different submerged sand deposits denominated ‘‘Massa’’, located 16 km offshore from the outlet of the Serchio river, at a water depth ranging between 40 and 100 m, and ‘‘Piombino’’ with water depth from 60 to 90 m but with bottom characterized by a much more irregular morphology (Fig. 1). Sampling strategy was developed in order to characterize both vertical and horizontal variability of both sand deposits. Four georeferenced (WGS-84) replicates were located per km2, for a total of 58 sampling stations: 36 in the Massa deposit (codified as M1M36) and 22 in the Piombino deposit (codified P1P22). In each sampling station, a 6-m-long core was collected using a SHSBD-AÒ core tube; three analytical levels were selected from each core at different depth levels (superficial, middle and deep samples) depending on the core length and following the sampling strategy proposed by the specific Guideline published by the Central Institute of Applied Marine Research (APAT-ICRAM, 2007). A total of 174 sediment samples were collected from the Massa and Piombino continental shelf deposits for physical, chemical, microbiological and ecotoxicological characterization. Twenty-one beaches (codified from b. 1 to b. 21 moving from north to south) threatened by erosion were characterized along the Tuscan coast to evaluate sand compatibility with the continental shelf deposits (Fig. 1). For beach sampling, three superficial sediment samples (0–50 cm) were collected directly using a Teflon pre-conditioned spatula at each sampling site (for a total of n = 63 observations). Collected samples were homogenized, stored in HDPE bottles and kept at + 4 °C until the time of analyses. Analyses were performed on variables of interest as per Italian Law (Decree Law n. 319, 1996) and following the APAT-ICRAM Guideline (2007). 2.2. Textural analysis Sediments were dry sieved at ½ phi intervals after removing and weighting fines ( LCBs) was observed. Trace element levels are low, with the exception of Cr and Ni, which are higher than relative LCBs. Beaches in Pisa are characterized by a measurable concentration of hydrocarbons (Serchio River – Arno estuary, (b. 4) Also HCB, PCBs (b. 4 showed values higher than LCBs), and pesticides are measurable and in some cases (b. 7) higher than LCBs. Levels of Cr and Ni are higher than LCBs (b. 4). Livorno beaches are characterized by low levels of total

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Fig. 3. Mean grain-size (Mz, phi) of sediments in Massa (A) and Piombino (B) deposits. Black lines represent 2.0 phi.

organic carbon and phosphorous with higher total nitrogen values particularly in samples located in the southern part of Vada, in the Gulf of Baratti and in the Southern part of Piombino. Total hydrocarbons are low, with higher values only occasionally found (b. 14). Pesticide levels are also higher than LCBs in some samples from these threatened beaches (b. 8, b. 13). High levels of As, Cr, Ni are observed, exceeding LCBs and, in some cases LCL as well. Particularly high levels of Cr, Ni and Zn are observed in samples from Cecina beaches (b. 9, 10, 11). In Grosseto, threatened beaches show low levels of total organic carbon and phosphorous, while higher values of total nitrogen are observed. PAHs are lower than detection limits in all collected samples with the exception of Fluorene (b. 16), measured at concentrations higher than LCB. PCBs values are higher than LCB at only one sampling site (b. 17) but pesticide values are frequently higher than LCB (b. 16, 17, 19, 20). Concerning trace elements, As, Cr and Ni evidenced values higher than LCBs in some threatened beaches from the Grosseto area (b. 17, 20), and Zn is higher than LCBs in two beaches (b. 20, 21). Concerning marine deposits, macronutrients (TOC, TN, TP) in all samples were found at levels notably lower than those reported in the literature for polluted areas in Italy (i.e. harbors and lagoons) (Renzi et al., 2007, 2009). Furthermore, reference values for nutrients are neither established by Italian legislative decree nor by ISPRA Guidelines. Analysis revealed an absence of significant contamination by organic pollutants (linear aliphatic hydrocarbons, PAH, PCB, pesticides). A few samples evidenced Lindane (M02, M09, M26) and/or total DDEs (M09, M10) higher than LCBs. Levels of trace elements in silts were relatively lower than LCBs, with the

exception of Cr and Ni in some samples. Sands evidenced a similar situation, with trace element levels lower than LCBs, with the exception of Cr and As in four samples. Experiments were performed to define speciation of trace elements with the aim of evaluating the bioavailability of As, Cr, Ni and determining whether observed levels might represent a significant risk for the marine environment. The exchangeable fraction of As was close to 5 mg/kg for each sample. The concentration of the exchangeable fraction of Cr was very low, close to LOQ. Levels bound to iron and manganese oxides are also very low, while Cr levels bound to organic matter are higher (5.1–10.2 mg/kg): about 8% of the total amount. The exchangeable fraction of Ni was between 4.2 and 10.2 mg/kg (7.7–14.4% of the total amount). The Piombino deposit is characterized by homogeneous physical–chemical values, while on the contrary, the Massa area is characterized by heterogeneous values. In this case, with regard to Cr and Ni, the residual fraction linked to sands is about 70%, lower than the percentage observed in Piombino.

3.4. Biological issues All of the threatened beaches under consideration show an absence of recent or previous microbiological pollution, but some ecotoxicological alterations can be observed. At Pisa-province beaches, medium toxicity was observed with regard to P. lividus (M5, M7), and in Livorno-province beaches, the same test evidenced at least medium toxicity for all samples, and high toxicity at one site (M14). The same situation is observed in Grosseto-province

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beaches, for which medium/high toxicity was observed for all tested samples with P. lividus. Concerning marine deposits, microbiological analysis revealed the absence of recent and remote pollution in both sandy and silty sediments. Human pathogens as well as Salmonella, mycetes and enteroviruses were below quantification limits. Bioaccumulation tests performed using the species Hediste diversicolor evidenced the absence of clear bioaccumulation for As and Cr in sediments sampled from the Massa deposit, while low Ni availability was reported (M21). It should be noted that Ni levels in sediments in this area are very low, falling below the LCBs defined by APATISPRA (2007). The same situation was observed in sediments collected in the Piombino area. Ecotoxicological tests performed on three species evidenced a general absence of toxicological effects for the species V. fischeri. Results of ecotoxicological tests performed on P. lividus evidenced toxicity for only one of the superficial silty sediments tested (M26). About 1/3 of the analyzed sand samples evidenced toxicity (P. lividus); it should be noted that EC20 values calculated in these samples are between 70% and 80% for C. orientale, with acute toxicity found in only one sample (M31).

3.5. Grain-size stability evaluations To evaluate nourishment compatibility, dry beach and nearshore sediment grain-size distributions were compared with that of some composite samples formed with suitable core layers from the Massa and Piombino deposits; all of the composites have a 3.0 phi modal class, indicating that they are finer than beach sediments. The Stability index (Is) value is influenced by the secondary mode at 1.0 phi, present in borrow material (Fig. 4). At Marina di Carrara (b. 1) a 250-m-wide nearshore strip was considered, but due to the presence of nearshore bars, water depth is between 1.64 and 4.94 m. Twenty-one samples taken here represent a coastal strip 1400 m long. The stability index ranges from 0.479 to 0.651 and may be higher if some fines are lost during dredging activity. The area of Marina di Massa (b. 3) lacks any shore parallel defense structure, which could interfere with operations and prevent further cross-shore sediment displacement. Sediment collected at 3.0 m (n = 11) was considered to be native material representing 3200 m of coast. The Stability index (Is) is between 0.643 and 0.469. Sand sampled in San Rossore (b. 4) was between 2.0 and 4.5 m and, with the exception of Composite n. 5 (Is = 0.568), all other samples have Is lower than 0.5, or in some cases even lower than 0.4, excluding the possibility of their utilization in this area. For the Cecina beach area, a coastal segment 1200 m long south of the groins protecting the two beaches was considered (b. 11). The swash zone comprised mixed sand and

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gravel sediments due to the discharge of coarse material over time, but the nearshore from 2 to 4 m comprises fine to medium sand. The Stability index for the Massa sediment is between 0.553 and 0.706 (the highest value is for Composite n. 5), and for the Piombino source the Is index is similar, between 0.565 and 0.604. Both the sites are therefore suitable for nearshore nourishment at Cecina. Concerning the East coast of the Follonica Gulf, the only place where nearshore nourishment could be done would be its western side (b. 14), where the Posidonia oceanica meadow is very limited due to the turbidity of water discharged by the Cornia River. A composite sample (n = 23) representing a 5.5 km stretch of coast is considered; for the entire area, the Stability index is consistently higher than 0.5 (0.563 < Is < 0.602). In the Rocchette beach area (b. 17), ten samples collected between 1.90 and 4.10 m water depth represent 2 km of coast. All the borrow sediment composites have Is higher than 0.5, the best being Composite n. 7 with Is = 0.527. In cases of coarser fraction moving into the swash zone, an increase in grain-size must be considered, with grains not frequently found in native sand. In the Albegna North area (b. 21), native nearshore sediments are represented by 8 samples collected between 2.4 and 3.5 m along 2000 m of coast, where sediments are quite homogeneous, with Mz between 2.09 and 2.99 phi. These are finer than Piombino composites, and Is ranges between 0.561 and 0.606, showing good stability. 4. Discussion The observed presence of a silt cap that covers offshore sands and is thicker in the Massa deposit than in the Piombino one observed in this study was consistent with the literature (Chiocci et al., 2008). A general homogeneity in terms of colour was recorded for sands sampled in both deposits, however, the colour of threatened beaches varies significantly even within the same physiographic units. This occurrence is particularly evident between Vada and Torre Nuova, where the northern sector of the physiographic unit is fed by white carbonate sand discharged by a still-active local chemical plant, while the Cecina River, feeding the central and southern part of this physiographic unit, delivers dark sediments to the coast. The southern Tuscan area fed by the Ombrone river is much more uniform. From a management point of view, colour variability in sediments along the Tuscan coast constitutes a positive factor for the use of marine aggregates, increasing the chance of finding uses for the various sediments available. 4.1. General aspects related to potential offshore aggregate utilization In Italy, marine sediment dredging for beach nourishment purposes is authorized following physical–chemical and

Fig. 4. Granulometric distribution of composite samples considered as representative of offshore marine deposits.

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microbiological characterization of sediments, as indicated by a specific Legislative Decree (Legislative Decree n. 319, 1996). The Legislative Decree does not propose reference values for the indicated variables of interest for dredging operations, but the APATICRAM Guideline (2007) supplements the Legislative Decree, including some chemical parameters and ecotoxicological analyses, and suggesting different frequencies of samplings and levels for the collection of sediments. Furthermore, it defines acceptable concentrations in marine sediments for organic pollutants and trace elements. APAT-ICRAM Guideline (2007) is not prescriptive, but stakeholders often adopt it as a sort of self-regulation during the decision process that must be gone through in Italy to obtain authorization for sediment dredging. Two different levels of acceptable limits of concentration in marine sediments are defined in this Guideline: the maximum value defining natural concentrations (LCBs) and the level indicating sediment pollution (LCL). LCB and LCL levels are not defined for Al, which is one of the principal components of the earth’s crust. In spite of the overall value of this approach (also known as the concentration limit approach, CLA), its application in Tuscany involves some significant issues. In fact, marine sediments here frequently exceed LCBs defined for trace elements due to the natural geochemical anomaly of this area. For example, in the Elba-Argentario basin, a wellknown geochemical anomaly due to trace element enrichment related to its volcanic origin is documented in the literature (Leoni and Sartori, 1997). Therefore, an exhaustive risk evaluation related to sediment dredging in these marine areas cannot be performed solely on the basis of application of the APAT-ICRAM Guideline (2007) criteria, since observed levels could be due mainly to the residual phase determined by the crystal structure of the sediment (Tessier et al., 1979). So, to evaluate the concrete bioavailability of observed levels, several other methods could provide useful information, namely: (i) sequential extractions procedure; (ii) bioaccumulation tests; (iii) ecotoxicological tests. Trace elements are naturally present in sediments due to their affinity with silt, iron and manganese oxides (Gadd, 2008). For this reason, knowledge of total trace element levels in sediments is not sufficient to correctly evaluate sediment quality, but through the determination of various trace element fractions, their bioavailability could be more accurately estimated, due to the different environmental mobility of chemical types (Tessier et al., 1979). In bioavailable fractions of offshore marine deposits, measured levels of As, Cr and Ni are not critical. These results support the hypothesis that observed trace element values exceeding LCBs defined by the APAT-ICRAM Guideline are not bioavailable, and are in fact based on geologic origin. This is also supported by the Cr/Ni ratio, which is close to 1:4 for almost all the samples. This value is indicated in the literature as suggesting a geological origin for these elements (Bowen, 1979). Polychaeta represent 70–90% of the sediment micro-fauna, including water-filter-feeding and detritivorous fauna (Eriksen et al., 1989). Trace element levels measured in tissues of these organisms are proportionate to environmental levels (Bryan et al., 1980), and are considered to be good indicators of trace element pollution. For these reasons, the absence of As and Cr bioaccumulation in exposed exemplars of the species Hediste diversicolor is important for stakeholders to consider during the decision process related to sediment dredging, and should be included in Guidelines and Laws on this matter. Furthermore, the bioaccumulation observed for Ni was unexpected on the basis of the CLA approach, as levels of this element found in sediments were below Guideline-specified limits. Several ecotoxicological tests were developed and applied to improve classical approaches based on traditional techniques, promoting the quali-quantitative evaluation of biological effects produced by the bioavailable fractions of environmental pollutants

including xenobiotics and trace elements (Volpi-Ghirardini et al., 2001). The species V. fischeri is used to evaluate toxicity of elutriates while C. orientale responses are reliably associated with direct toxicity of sediments (ISPRA, 2011). The lack of response to exposure of these two species owing to different ecological and trophic levels may suggest a general absence of toxicity of measured trace element concentrations. However, the responses observed in P. lividus were unexpected and difficult to explain, since the sedimentary component considered in the literature to be the main cause of sediment (silt) toxicity appeared to have no effect on the biological component in almost all tested samples, while sand was shown to produce greater effects, and thus to be of greater concern. As evidenced by the results obtained in this study, the application of the CLA proposed by the APAT-ISPRA Guideline is not exhaustive, particularly concerning the occurrence of trace element outliers where natural geochemical anomalies are present. In fact, excess trace elements may not necessarily indicate pollution in sediments, and/or could be related to some ecotoxicological, biological and ecological effects. The integrated approach applied in this study, which includes the evaluation of bioavailability by means of different strategies – selective extractions (chemical tests), bioaccumulation analysis in Hediste diversicolor, and ecotoxicological tests on C. orientale (a benthonic species which lives burrowed in sediments) – could be useful for a more complete and exhaustive risk assessment. An important aspect emerging from this study is the general occurrence of higher sediment pollution observed in threatened beaches than in marine deposits. This should be a strong input for legislators and scientists to develop better regulations and references to evaluate beaches from a health point of view and to plan opportune management actions geared towards ecosystem conservation and restoration, and not aimed solely to ensure the exploitation of marine resources for summer tourism purposes.

4.2. Dry beach nourishment Dry beach nourishment is one of the potential utilizations of offshore aggregates for the beaches in question. Concerning the sediments available in the Massa deposit, analysis of their compatibility for beach nourishment was carried out considering only the northern Tuscan coast (Magra River – Livorno), since their low stability does not justify significant transport expenses. However, these sediments are stable only on the southern segment of this sedimentary cell, as these beaches contain the finest sediments of the entire coastal area considered in this study. The site is currently in need of planning, since the expansion of the Livorno harbour induced an up-drift erosion (Cappietti et al., 2003) extending up to Calambrone. Colour compatibility is good, with DE⁄ab consistently lower than 9. There is little opportunity to use available aggregates in eroding segments of this cell, possibly to be extracted from single layers with limited lateral continuity and with unsustainable costs. Marina di Massa could host sediments extracted from the furthest offshore deposit, where sands ranging from slightly coarser to slightly finer than the native ones are present; their colour is generally compatible, but some samples are near the acceptable limit. Comparing Piombino sediments with those present on the Tuscan coast as a whole, limitations to their utilization emerge, although less significant than those encountered with Massa sediments. Their larger size broadens their possible use to areas effectively seeking beach nourishments: the Gulf of Baratti (b. 13), native sand size (Mz) is 1.33 to 2.05 phi; on Follonica Bay (b. 14, 15), where sand is 1.65 e 2.39 phi, and at Punta Ala (b. 13; Mz = 2.42 phi in the central and southern sectors). The advantages of using this source are that the upper layer is very thin and could

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be mixed with deeper sediments to be applied for beach nourishment. 4.3. Nearshore nourishment Since sediments available in off-shore deposits would not be stable on the dry beach, but their colour is compatible with native ones, nearshore nourishment has been considered, following examples from several European countries (e.g. Belgium, Denmark, The Netherlands; Charlier, 2013; Sørensen, 2013; van der Meulen et al., 2013). Advantages are: (i) the possibility of using dredges with larger drought, (ii) no interference with tourist beach use; (iii) the whole fill is reshaped, washed and sorted by waves so that each grain-size population migrates to its natural position, (iv) nearshore rising favors wave energy dissipation, (v) finer-thannative sediments can be utilized. Based on the needs for sediments to serve projects currently being carried out by the Region of Tuscany, the characteristics of available aggregates at the two sites and the distance to be covered, a preliminary plan for the use of the offshore sediments was drawn up. From Massa, approximately 1,000,000 m3 of sediments are potentially to be used for nearshore ( 2 to 4 m) nourishment at Marina di Carrara (200,000 m3), Marina di Massa (500.000 m3) and the northern beach of San Rossore (300,000 m3), all to be executed in a single project so as to optimize mob/demob costs. In this case, even though deeper layers contain good sand, the environmental and economic costs of dredging prevent their use at present. The Piombino deposit could provide sediments for Cecina Mare (b. 10, 11; 300,000 m3), Follonica (b. 14, 15; 400,000 m3), Le Rocchette (b. 17; 200,000 m3) and Foce Albegna (b. 21; 250,000 m3). Some environmental constraints exist in these areas, particularly at Follonica, where there is a Posidonia oceanica meadow close to the beach. In this case, specific barges are required to discharge sediments in the proper position, and rainbow nourishment is prohibited. Therefore, two separate projects will be necessary: one for Follonica, and the other for Cecina, Le Rocchette and Foce Albegna. To evaluate the textural compatibility of the source sediments with the native one, the nearshore sediment archive of the University of Florence was used. 4.4. Feasibility study A critical aspect affecting beach nourishment practices concerns the method to be used for the harvesting of sediments of suitable grain size. A preliminary comparison between dredgers’ (static suction dredger vs. trailer suction dredger) performance was part of the feasibility study to select the optimal solution. The opportunity to apply sediment screening procedures was evaluated; in addition, a preliminary estimation of possible volumes and frequency of extraction from the borrow areas was made. The depth of the borrow areas significantly limits the typology of suitable dredgers. In fact, mechanical dredgers are not suitable for depths of more than 30 m; suction dredgers based on hydraulic technology are better for deeper sites. Trailing suction hopper dredgers combine dredging and transport functions and are frequently used for harbour dredging, beach nourishment and deepsea dredging activities. In particular, the depth of the Piombino and Massa borrow areas (between 40 and 100 m) imposes the use of larger instruments to ensure better vessel stability during dredging procedures, for safety reasons as well. Currently only few dredgers in the world, such as ’’Mega-dredgers’’ (carry capacity over 20  103 m3), can ensure such performance (Bruun et al., 2005). Another critical point to be resolved before dredging in the Piombino and Massa borrow areas is the thick superficial capping layer of silt, which increases general costs. Capping layers can be handled using various methods, including: (i) selective elimina-

tion of the finest sediment fractions by sorting of the entirety of the sediment dredged; (ii) in situ by-pass of the capping layer by means of ‘‘syringe’’ perforation techniques; (iii) preliminary elimination of the capping layer and storage of the silt in opportune areas to make lower strata of sands accessible to dredgers. Among these three technical options, the use of ‘‘syringe’’ method reduces the environmental impact of silt fraction management, although plumes are unavoidable in any dredging operation (Dredging and Port Construction, 2000). Although from the chemical, biological, ecotoxicological and colorimetric point of view there are very limited constraints to the use of sediments available at the two potential quarries at Massa and Piombino for artificial nourishment of beaches in Tuscany, their grain size severely limits such use. Numerous potential environmental impacts could arise from dredging activities and beach nourishment practices. Impacts on the Piombino and Massa borrow sites would be mainly due to the capping removal procedure applied and to sediment losses and resuspension during dredging that could affect water turbidity and nutrient and pollutant release from sediments (Wainright and Hopkinson, 1997; Fanning et al., 1982; Blackburn, 1997; Amado Filho et al., 2004; Gopalakrishnan et al., 2008), seabed topography with possible consequences on marine currents (Jensen and Mogensen, 2000) and seabed sediment types, which could directly and indirectly affect benthic faunal and photosynthetic communities with possible alteration of the structure of biological communities (Bonvicini Pagliai et al., 1985; Newell et al., 1998). Furthermore, there are protected marine areas in the vicinity of the borrow sites (Secche della Meloria Marine Protected Area), as well as the Marine Mammals Sanctuary (Pelagos), which are subject to specific regulations. Potential impacts are also linked to disposal phases, which could directly and indirectly affect P. oceanica meadows (Short and Wyllie-Echeverria, 1996; Duarte, 2002; Erftemeijer and Lewis, 2006) and benthic communities. To avoid possible negative effects on biological communities in both borrow sites and receiving beaches, appropriate monitoring plans should be drawn up, andeffects on marine mammals should be monitored. The volume of sediments dredged and discharged should be opportunely planned, and the process should be halted if significant impacts are observed during monitoring of one or more environmental components, to allow impacted sites to recover and re-establish optimal conditions. It is important to be aware of the possibility of an increase in the overall cost of beach fill operations due to adjustment made in response to information obtained through monitoring.

Table 2 Estimation of costs*. Borrowing site - Fill area

Quantities M01  M22** M34  M36 Piombino [m3] [€/m3] [€/m3] [€/m3]

Massa – Marina di Carrara 200.000 Massa – Marina di Massa 500.000 Massa – San Rossore 300.000 Piombino Piombino Piombino Piombino Piombino

– – – – –

Cecina Follonica Punta Ala Castiglione Albegna

300.000 400.000 200.000 200.000 250.000

23.86 26.89 25.79

14.02 13.88 12.80 14.58 14.46 14.58 14.99 17.92

* Some general remarks on estimations are: i) Sand will be pumped ashore and spread out with dozers, no spraying is considered (too much weather dependent); ii) No demining considered; iii) No overflow or other environmental restriction considered; iv) Reduction or further split up of the volumes (e.g. more beaches for the same volume) will impact the unit rates; v) One of Jumbo Trailer Suction Hoppers can be mobilized from South America or the far East, depending on availability (Mob-demob 10-15.000.000 €). ** M01  M22 sediments are significantly coarser, thus reducing the production and increasing the wear & tear.

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4.5. Cost-benefit analysis A preliminary cost estimation is reported in Table 2 (repeat dredging was not considered due to the high cost of mob-demob). In addition, planners must carefully consider the cost of dredging operations at water depths greater than 70 m. Mega-dredgers capable of doing the job are not normally present in the Mediterranean (as they are in UAE, Far East, South America; Bruun et al., 2005), thus mob-demob costs are substantial. For this reason, the cost of sand pumped and moved along the beach will be € 15–20 per cubic meter only if very large volumes (more than 1 million cubic meters of aggregates) are dredged. Since it is quite difficult for a single Regional Authority to coordinate several beach nourishment interventions synchronized with the presence of a Mega-dredger, another option would be to coordinate coastal restoration work among several Regional administrations, in order to reduce the cost of the sand (dredging + transport + deposition). The knowledge gathered through the BEACHMED Project in cooperation with EU Dredging Association points in this direction (www.beachmed.eu – ReSaMMé sub-project, Lupino et al., 2004), as does the experience of the COST 638 Action MAGGNET and MAREMED Project (www.cmgizc.info). Cost aspects related to sediment dredging and beach nourishment are currently key to coastal management and conservation plans, and will be of growing interest for communities and stakeholders due to the predicted effects of global warming phenomena on sea levels. The PESETA Project shows that by 2020 approximately 70 million cubic meters of aggregates will be required in the Mediterranean area, and that among adaptation strategies, beach nourishment may be a good management practice. However, environmental constraints and the limited financial resources of the Regions mean the idea must remain in the planning stages for the moment. The latest Regional data on shoreline evolution between 1984 and 2010 shows that the Tuscan coast lost more than 800,000 m2 of dry beach during that period. In particular, approximately 35.9% of its continental beaches, corresponding to 72 km, experienced shoreline retreat of more than 5 m. It has been estimated that 100,000 m2 of replenished beach could generate € 3,000,000 per year for beach activities directly linked to summer tourism. This value rises to € 120,000,000 per year when activities indirectly linked to the increase in summer tourism are considered. Therefore, even though estimated costs are substantial and exceed the Region’s normally available resources, the balance sheet for planned beach nourishment could be considered positive (CIBIM et al., 2011).

5. Conclusions This research highlights some important aspects linked to beach nourishment problems. First and foremost, current laws and technical guidelines on this matter should be significantly improved to provide for correct evaluation of sediment compatibility in marine areas affected by geochemical anomalies, and should include integrated physical–chemical and ecotoxicological approaches that are better able to evaluate ecotoxicity and bioavailability of pollutants. Furthermore, aspects related to microbiological pollution, colour and grain-size compatibility should be given greater consideration in guidelines. The frequently observed case of beach sediments that are more polluted than marine deposit ones should be considered to give to stakeholders the appropriate technical instruments to make decisions. The cost-benefit analysis performed showed that dredging of small quantities of sediments would entail significant costs that could not easily be covered by public administrations. A preliminary feasibility study on dredging indicated that

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