Journal of Coastal Research 21 3 472–481 West Palm Beach, Florida May 2005

Artificial Construction of Dunes in the South of PortugalAna Matias†, Oscar Ferreira‡, Isabel Mendes†, Joao A. Dias‡, and Ana Vila-Concejo†

†CIACOMAR—Universidadedo Algarve

Avenida 16 de Junho, s/n8700-311 Olhao, Portugalammatias@ualg.pt

‡Faculdade de Ciencias doMar e do Ambiente—Universidade do Algarve

Campus de Gambelas8005-139 Faro, Portugal

ABSTRACT

MATIAS, A.; FERREIRA, O.; MENDES, I.; DIAS, J.A., and VILA-CONCEJO, A., 2005. Artificial construction of dunesin the south of Portugal. Journal of Coastal Research, 21(3), 472–481. West Palm Beach (Florida), ISSN 0749-0208.

The Cacela Peninsula on the south coast of Portugal was, previous to nourishment operations, extremely vulnerableto overwash events. During the 1995–96 winter, extensive overwashing led to the opening of a new inlet. Simulta-neously, the lagoon channel in the backbarrier was silting up with the overwash deposits, inlet flood delta sands, andaccretion of fine sediments.

Between October 1996 and February 1997 the channel was dredged, and the sediments were deposited on thewestern 2,000 meters of the Cacela Peninsula, forming an artificial dune ridge. The sediment characteristics of thedredge spoils were in contrast with the natural dune sand. The spoils had higher silt and clay content, lower meangrain size, and poorer sorting. In January 1998, three washover breaches were infilled, with sand removed from theforeshore, on the eastern part of the Cacela Peninsula. These sands were coarser and more poorly sorted than theoriginal dune sediments.

A 2-year monitoring program, consisting of beach/dune profiling, topographic surveys in specific areas, and sedimentanalysis, was established to observe the morphological evolution of these areas.

The total eroded volume recorded for the dune nourishment project after 2 years was about 106,500 cubic meters,corresponding to 33% of the total 325,000 cubic meters of sediment that was deposited. The washover infilling showedlittle or no variation. However, the downdrift beaches and foredunes experienced severe erosion.

Both protective measures accomplished their purposes in terms of preventing erosion; however, a natural landscapewas only created where dune development by aeolian processes was possible.

ADDITIONAL INDEX WORDS: Dunes, nourishment, grain size, dredging spoils, South Portugal.

INTRODUCTION

Many previous authors have described the fundamental as-pects of beach nourishment project design (e.g., DEAN, 1988,1996, 1998, 2002; HOUSTON, 1991, 1996; KANA, 1989, 1993,1996; NATIONAL RESEARCH COUNCIL, 1995; US ARMY

CORPS OF ENGINEERS, 2002). However, description and anal-ysis of specific dune nourishment methods are relativelyscarce, although they have been used on the Dutch coast tobring the dunes in line within a pre-established safety stan-dard (VAN DER WAL, 1998).

Beach nourishment is still used infrequently in Portugal,even though the case first described occurred about 50 yearsago, from 1950 to 1954 near Lisbon (MARTINS, 1977). Thecommon practice in Portugal of dealing with coastal erosion

DOI:10.2112/03-0047.1 received 17 March 2004; accepted in revision24 March 2004.

This work is a contribution to the PRIMO project—Prediction andImpacts of Runup and Overwashes—under contract 39849/CTA/2001. The authors also thank the Instituto da Conservacao da Na-tureza for complementary financial support. Ana Matias was sup-ported by the Fundacao para a Ciencia e a Tecnologia, grant SFRH/BD/1356/2000. Ana Vila-Concejo acknowledges the partial supportof the INDIA project under the European Union Marine Sciences andTechnology program (MAS3-CT97-0106) and the CROP project(Cross Shore Processes on Contrasting Environments) under con-tract PDCTM/MAR/15265/99.

is the construction of groins and seawalls (DIAS, 1990). Theserigid structures have been criticized extensively because theypromote further erosion downdrift, need constant costlymaintenance, provide an artificial landscape, and give a falseperception of safety that frequently leads to errors in urbanexpansion. Beach nourishment, however, constitutes an en-gineering shore protection alternative of adding sand, pref-erentially from sources outside the eroding system. Typicalsediment sources are navigation channels, sand bypass sys-tems, inlet ebb tide shoals, and offshore borrow areas (CLAY-TON, 1989; HOUSTON, 1991, 1996; WIEGEL, 1994).

In this work, two dune nourishment projects are describedand analyzed with the use of 2 years of postnourishmentmonitoring data. This case study constitutes one of the lon-gest monitoring programs of nourished areas in Portugal.

STUDY AREA BACKGROUND

The study area is the Cacela Peninsula, the eastern limitof the Ria Formosa barrier island system, Algarve, Portugal(Figure 1). It is separated from the westward adjacent Ca-banas Island by the Lacem Inlet.

The recent evolution of this peninsula (since the 1940s) ischaracterized by a significant narrowing of the Cacela Pen-insula dune field, especially during recent times (from 1989to 1996; MATIAS, FERREIRA, and DIAS, 2000). This width re-

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Figure 1. Location of the Cacela Peninsula as a part of the Ria Formosa barrier island system (Algarve, Portugal).

duction was primarily from foredune erosion, with the con-sequent shoreline retreat, as a result of an increase in wash-over breaches and density of access paths. A maximum shore-line retreat value of 123 meters was determined in the west-ern part of the peninsula for the period between ;1940 and1996 (MATIAS, 2000).

During the last three decades, about 77% of the dune areaof the Cacela Peninsula has been eroded. In 1996, the wash-over breaches represented 71% of the dune field area on thewestern half of the peninsula.

The recent evolution of the Cacela Peninsula is character-ized by a general sediment deficit, inducing coastal erosion,together with a landward displacement of the entire dunefield, as previously mentioned by PILKEY et al., (1989), AN-DRADE (1990), BETTENCOURT (1994) and MATIAS, FERREIRA,and DIAS, (2000).

During the 1995–96 winter, overwash events completelybreached the dune field, which led to the opening of a newinlet approximately in the center of the peninsula (Figure 2).This inlet was named Fabrica Inlet and had a width of about35 meters at low tide and a maximum channel depth of 0.7meters below mean sea level (MSL; MATIAS et al., 1999). Thelagoon channel, which separates the barrier peninsula fromthe mainland, was in an accelerated silting up process. Theoverwash deposits, the flood tidal deltas, and the depositionof fine sediments on the salt marsh areas generated a shallowand narrow channel over the years.

In the mid-1990s, the reference situation for Cacela Pen-insula was that of an extremely fragile dune system with a

lagoon channel on its landward side that was being infillednaturally.

OCEANOGRAPHIC SETTING

The tidal regime in the study area is semidiurnal, with amean tidal range of 2.0 meters, reaching about 3.4 meters onspring tides. The offshore wave climate is dominated by thewesterly swell waves, about 50% of occurrences, with south-easterly waves also being relatively frequent (about 25%;COSTA, 1994). The annual value for mean offshore significantwave height (Hso) is 0.92 meter (medium energy; COSTA,1994). However, the southeasterly orientation of Cacela Pen-insula provides a sheltered location with respect to the longerfetch westerly waves. Therefore, on this coastal stretch, thewave climate is dominated by small, intensely refracted spill-ing breaker waves. For example, in 1997 and 1998, Hso wasabout 1.0 meter, whereas the mean breaking significant waveheight (Hsb) was 0.6 meter (MATIAS, 2000).

Storms have been defined for the south coast of Portugalas events in which Hso is higher than 3.0 meters (PESSANHA

and PIRES, 1981). The most frequent storm waves affectingthis coast correspond to southwesterly refracted waves (Hsb

of 2.6 m), the southeasterly storm waves are less frequentbut higher in amplitude (Hsb of ;3.2 m; MATIAS, 2000).

Longshore currents are generally from west to east, withestimates of littoral drift for the study area of about 100,000m3/y, according to ANDRADE (1990), and between 120,000 m3/y and 150,000 m3/y, according to BETTENCOURT (1994).

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Figure 2. Aerial oblique view of the central and western part of the Cacela Peninsula, with the Fabrica Inlet, before dune nourishment. Date: 17 October1996.

Figure 3. Aerial oblique view of the western part of the Cacela Peninsula after dune nourishment. Date: 9 December 1997.

DUNE NOURISHMENT OBJECTIVES AND DESIGN

The dune field on Cacela Peninsula was extremely vulner-able to overwash in 1996, leading to dune deterioration andpromoting sand deposition inside the lagoon. Also, the Fa-brica Inlet was located in front of Fabrica village, and if thisinlet expanded, the shorefront could be damaged. The LacemInlet channel was narrow, shallow, and undergoing a mean-dering process, which could have led to its closure in a shorttime.

The nourishment was intended to artificially construct thedunes and close the recently opened inlet. The dune top ele-vation was projected to reach 5.5 meters above MSL in anattempt to reconstruct the 1960s situation.

Nourishment was made with sediment dredged from the

inner channel and from Lacem Inlet channel and flood delta.The dredging objectives were to increase depth, both of thelagoon and the inlet channels, until they reached 24.0 me-ters, in relation to MSL, to facilitate small boat traffic and toincrease water circulation inside the lagoon system, whichwould bring benefits to clam and oyster aquaculture activi-ties.

The dredging and nourishment operations were performedfrom October 1996 to February 1997. The dredge spoils weredeposited on top of the existing dunes, affecting the western2,000 meters of the peninsula (Figure 3).

The comparison between surveys performed on the channelimmediately before and after the dredging showed that a to-tal of 480,000 cubic meters of sediment was removed from

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Figure 4. Location of the recent interventions performed at Cacela Peninsula, with the position of the monitored profiles.

this area. However, dredging was not performed to the de-signed depth because rocky outcrops prohibited deeper dredg-ing, the outcrops were composed of fossiliferous marls. Thisresulted in smaller amounts of dredged material than pre-dicted by the initial project. The sediments removed from thechannel were heterogeneous, both in composition and ingranulometry, including a fine fraction that was partially lostto the sea by dewatering of the dredge slurry after placement.

The sediments were placed on the peninsula, completelycovering the existing dunes, resulting in an elevation thatdecreased from the projected 5.5 meters above MSL at thewestern part to 3.5 meters above MSL in the east because ofa lack of sediments. At the Fabrica Inlet, sediment depositionfollowed the morphology of the inlet flood delta, creating are-entrant, landward curve-like shape in the nourished area.

Topographic surveys conducted before and after construc-tion allowed a general computation of the total in-place nour-ishment volume. About 325,000 cubic meters of sediment re-mained on the peninsula immediately after nourishment, im-plying a loss of about 32% of the dredged material from thedewatering of the dredge slurry (DIAS et al., 1999; MATIAS etal., 1998, 1999).

The total cost of the project was about 294 million Portu-guese escudos (approximately €1.47 million or US $1.9 mil-lion in 1997), supported by Portuguese government environ-mental agencies.

In addition to the sediment placement, sets of wooden fenc-es were placed on the top of the eastern and central part ofthe nourished area (Figure 4) between April and August1997. The 1.3-meter-high fences were designed to form a lat-tice structure with interconnecting longshore and cross-shoresections, with a total length of about 1,000 meters. The twolongshore sets were separated by 6.4 meters and had perpen-dicular fence sections each 6.7 meters apart, thus forming

rectangles of 43 square meters. The objective of the fenceswas to trap sediments transported by the wind, as well asavoid disturbance by trampling. Two elevated footbridgeswere built to allow people to cross the dunes.

WASHOVER INFILLING OBJECTIVES AND DESIGN

Despite the protection of the western part of the CacelaPeninsula from overwash by dune nourishment, the easternpart was still vulnerable in relation to this process. Here, thelarge and deep washover breaches constituted fragile seg-ments in which a future disruption of the dune field couldoccur.

The artificial filling of the washovers was planned to gen-erate a continuous foredune in this area, with an upper ele-vation of 4.5 meters along 1,000 meters. Washover infillingoperations were performed in January 1998, and three wash-over breaches located eastward of the recently nourished areawere infilled (Figure 4). The source of the sand was the ad-jacent low-tide terrace of the beach. During this operation,approximately 15,000 cubic meters of sand was deposited ona total area of about 15,000 square meters. The project hadsmall sediment fill placement losses because the dredged sed-iments were generally composed of beach sands without asignificant percentage of fines (silts and clays).

The total project costs were 5,700,000 Portuguese escudos(about €28,000 or US $31,000 in 1998).

MONITORING PROGRAM

After the dune nourishment operations, a monitoring pro-gram was established consisting of monthly dune/beach pro-files performed at spring low tide. Eight profiles were select-ed, with a distance of about 400–500 meters between consec-utive profiles, giving a total survey length of 3,300 meters.

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Figure 5. Bluff edge retreat for profiles 1–4 during the monitoring period. Note that profile 1 measurements ended in December 1998 because of theloss of its origin, associated with the Lacem Inlet displacement

Five profiles (1–5) were located on the dune nourishmentarea; profile 6 was located on one of the infilled washovers,and profiles 7 and 8 were located eastward (downdrift) of thenourished areas (Figure 4). The monitoring period was be-tween March 1997 and March 1999. Data obtained from thedune/beach profiling were used for monthly morphologicaland volumetric comparisons, including the computation ofdune bluff retreat.

Two topographic maps (1 : 2,000 scale) of the western pen-insula were obtained immediately before and after the nour-ishment operation. These surveys allow a global nourishmentvolume computation. In November 1998, a survey was per-formed on the western edge of the nourishment to computethe volume changes induced by the Lacem Inlet displace-ment.

Samples were collected on the dredging vessel before thesediments entered the pipes and at the nourished sites afterdewatering on profiles 1 to 5. The dredged sediments werecollected between October and November 1996 and in Feb-ruary 1997. To analyze the variability of the spoils, a seriesof samples were taken at different heights on the nourishedseaward bluff on profiles 2 and 3. The washover filling sandswere also sampled at profile 6, with the samples taken atprofiles 7 and 8 being representative of the natural dune sed-iment characteristics. This analysis was to verify the granu-lometric compatibility between original and nourishment sed-iments for both interventions.

DUNE NOURISHMENT EVOLUTION

Morphological Evolution

The first morphological variation observed in the nourishedarea was the significant erosion of the seaward front that

occurred only a few days after the end of the dredging andnourishment operations. This was caused by a southeaststorm, with offshore significant wave heights reaching 3.4meters. This storm led to the erosion of about 33,400 cubicmeters corresponding to approximately 10% of the depositedsediments (DIAS et al., 1999). The erosion of the seaward frontof the nourishment was responsible for the formation of abluff of varying height, between a few centimeters (easternpart) to about 3 meters (western part).

One of the most significant evolutionary processes of thisarea was the retreat of the bluff edge with consequent nar-rowing of the nourishment. The bluff retreat was more in-tense at sites where the seaward front was relatively prom-inent (e.g., profile 3; 7.6 m in 24 mo; Figure 5) and smallersediment losses occurred at re-entrant sites (e.g., profile 4;0.6 m in 24 mo). At profile 5 (a re-entrant site), bluff forma-tion did not occur. These different exposures resulted fromthe dredged sediment deposition procedure: in the FabricaInlet zone, nourishment was made landward of the generalcoastline alignment, following the flood tidal delta of the in-let. On the basis of these different rates, it seems that astraight seaward nourishment front would be expected toform in the future, with continuing erosion of the prominentparts. The total sediment volume losses from bluff retreatrecorded during the 24 months of the monitoring period wasabout 20,450 cubic meters (i.e., 10.9 m3/m).

On the western edge of the nourishment, significant retreatwas also recorded (see profile 1 bluff retreat, Figure 5). Thissite constitutes the eastward margin of the Lacem Inlet. Afterthe inlet channel dredging, an eastward migration, togetherwith a meandering process, was observed, promoting erosionof the nourishment. This process was expected to occur be-cause, historically, this inlet migrates eastward (at least

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Figure 6. Mean size vs. sorting for the samples collected during the dredging operations, of the dune nourishment, of the washover infilling, of the sandinside the fences, and from the original dunes.

since 1972) at rates varying from about 2 to 160 m/y (MATIAS,FERREIRA, and DIAS, 2000). The inlet displacement was re-sponsible for the erosion of about 47,500 cubic meters of thenourished sediments.

In contrast to the general erosion noticed on the westernand central parts of the nourishment, some accumulation oc-curred on its easternmost part. The backshore was large, pro-viding aeolian fetch, and the nourishment elevation was low(,1.0 m) in relation to the previous surface. The aeolian sandtransport and accumulation led to the development of em-bryonic dunes on the backshore and to the formation of duneson the top of the nourishment, where the fences were placed.The computed volume for this accumulation was about 4,000cubic meters of sand on the eastern 620 meters of the nour-ishment (DIAS et al., 1999).

Comparison of profiles also showed some erosion on theinner edge of the replenishment caused by the tidal lagooncurrents. The erosion volume was about 5,100 cubic meters(i.e., 2.7 m3/m).

A general analysis of the nourished sediment losses showsthat, at the end of the monitoring period (24 mo after theoperations), about 218,500 cubic meters of sediment re-mained in the area (67%). From the total erosion, about 50%was because of seaward front retreat caused by wave action.The inlet displacement accounted for a loss of approximately45%, whereas erosion by inner lagoon processes was only 5%of the total amount of erosion.

Sediment Analysis

The Cacela Peninsula natural dunes are composed of me-dium sand (mean size 5 1.63f), well sorted and negativelyskewed. The variation of these parameters through time andalongshore was small, except in washover breaches (MATIAS,2000).

The dredged sediments were heterogeneous, showing uni-

modal, bimodal, and plurimodal grain size distributions, witha variable silt and clay content between 0.4% and 29.7%. Thegranulometric characteristics of these sediments are variable(Figure 6): from coarse to fine sands, poorly to moderatelysorted, and positively to negatively skewed. This high het-erogeneity is related to the different deposition conditions ofthe various environments of the source area. These includedtidal flats, alluvial fans, inlet deltas, overwash deposits, andlagoon channels. Depending on which part of the lagoon wasbeing dredged, different sedimentary characteristics could befound.

The comparison between the dredged material and thedune nourishment sediments shows a general reduction ofthe silt and clay content, an increase in mean grain size, bet-ter sorting, and more negative skewness. These differencesare related to the dewatering of the dredge slurry after place-ment, which transported a large amount of fine sedimentsinto the sea.

The samples taken at several heights of the artificial dunebluff also showed high variability (Figure 7). An inverse re-lation was observed between the mean grain size and sorting,with a good direct relation between the latter and skewness.These relations mean that the finer sediments are bettersorted and more negatively skewed, having a probable originin the lagoon channel or on the tidal flats. The coarser sandswith poorer sorting are probably from the tidal inlet deltasand channels. The highest fine sediment content was foundat the base of the deposit, which could correspond to sedi-ments from tidal flat areas or result from infiltration of finesduring the injection process when nourishment compactionwas being carried out.

Generally, the sediment granulometric analysis showedthat the artificially generated dunes differ significantly fromthe natural dunes in this area.

On the fenced area of the nourishment, the deposit gener-

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Figure 7. Granulometric parameters and fine fraction content of the sediments collected at several heights of the artificial dune bluff, on profile 2.

ated by the disruption of aeolian sand flow has granulometriccharacteristics similar to these coastal sand dunes (Figure 6).

WASHOVER INFILLING EVOLUTION

Morphological Evolution

Analysis of the washover filling area was made by moni-toring the dune/beach profile located on the washover (profile6). The two downdrift profiles were also considered for com-parison purposes.

Profiles 6, 7, and 8 show similar small volume variationsduring the period between March 1997 and November 1997(Figure 8). However, in the months after washover infilling(January 1998), the downdrift profiles experienced strongerosion, whereas profile 6 had a fairly constant volume. Thiserosion can be related to the storm periods that occurred be-tween January and February 1998, with the maximum off-shore significant wave height being higher than 5.0 metersduring one of the storms. On the other hand, the lack of sed-iments on the low-tide terrace of the adjacent beach, removedto fill the washovers, could also have contributed to the re-corded high sand volume losses. Because such erosion wasnot recorded on the updrift profiles, it is probable that stormeffects were amplified by the sediment removal.

During the monitoring period, no major losses were record-ed at the nourished breaches. Because its seaward limit issimilar to the natural foredune immediately to the west andeast, it is expected that this zone will follow the same trendsof natural dune evolution. However, it was noticed that noaeolian accumulation occurred on these areas, probably be-cause no obstacle to the flow (natural or artificial) exists. Infact, vegetation did not naturally colonize this area until theend of the monitoring period.

Sediment Analysis

The sediments used to fill the washover breaches were re-moved from the low-tide terrace of the beach. These sedi-ments had granulometric characteristics distinct from thenatural dunes (Figure 6). The sand was, generally, coarserand with poorer sorting, including high shell content, typi-cally absent on these dunes. Sediment characteristics aremore similar to those of the natural washover breaches thanto the aeolian/vegetation-built dunes.

DISCUSSION AND CONCLUSIONS

The Cacela Peninsula was an extremely vulnerable system,densely breached and with a low, poorly vegetated, single-crested dune field. As a consequence of the nourishment op-eration during the winter of 1996–97, the dune ridge top wasraised from about 2.5 meters average height above MSL to3.5–5.5 meters by placement of about 325,000 cubic metersof dredged sediments. The nourishment significantly changedthe morphodynamic behavior of the system. Before sedimentintroduction, overwashes were frequent and were responsiblefor significant dune destruction and silting up of the internalchannel. Because of the raised level of the dune crest, whichis now about 1.5–2.0 meters above washover throat elevationin the nearby areas, overwashes did not occur and are notexpected. However, some erosion occurred during the moni-toring period (2 y), inducing bluff retreat and making thenourished area narrower. The erosion took place preferen-tially on protruding sites and on the Lacem Inlet margin. Inlight of the present data, because part of the nourishment isstill prominent relative to the general alignment, a readjust-ment is still expected, with continuing erosion of these areas.

The global volume computation for the nourished area is

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Figure 8. Subaerial beach/foredune cumulative volume changes for profiles 6–8 between March 1997 and March 1999. Note that profile 6 measurementswere interrupted in January 1998 because the washover breach was being filled during this period and data collection was not possible.

Figure 9. Global cumulative volume variation of nourished areas for the monitoring period and mean historical erosion rates recorded for the periodaround 1940–96 (from Matias, Ferreira, and Dias, 2000).

positive (Figure 9). This balance results from the combinationof several coastal processes occurring on the nourishment andon the adjacent areas, namely dune nourishment seawardfront erosion, erosion induced by eastward inlet migration,aeolian accumulation on the top of the nourishment, embry-onic dune development on the backshore, and beach bermformation during fair weather conditions. However, it shouldbe stressed that the second winter of the monitoring periodwas less energetic than the first and significantly less severe

than the general winter conditions for the south coast of Por-tugal.

If historical rates had remained constant for the monitor-ing period, global erosion would have been expected (Figure9). Therefore, dune nourishment can be considered as gen-erally positive in terms of sedimentary balance because itsupplied the amount of sediments necessary to overcome thestructural erosion trend for the 2 years analyzed in thisstudy. On the other hand, dune nourishment produced an

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artificial landscape, with morphological and sedimentologicalcharacteristics contrasting with natural sand dunes. In plac-es where aeolian processes developed the dune/beach system,a more natural landscape was created. At the eastern part ofthe nourishment, the sand characteristics are similar to thoseof the previous natural dunes. Dune colonization by vegeta-tion is allowed, promoting aeolian sediment trapping andhabitat for dune fauna.

From the point of view of tourism, this part of the beachbecame more pleasant and attractive. Because elevated foot-bridges were built to cross the dunes, tourism, dune ecology,and erosion prevention is in a moderate equilibrium in thisarea.

On the western part of the dune nourishment, aeolian ac-cumulation occurred because the beach is narrow and theseaward bluff is high. As a consequence, the pioneer vegeta-tion was not re-established. In this case, erosion preventionwas successful (at least during the surveyed period), but eco-logical and sedimentological recovery did not take place.

The dunes of the eastern part of the Cacela Peninsula were,before nourishment, a vulnerable system in which washoverbreaches were a common occurrence. As a consequence of theartificial fill of these dune breaches, dune erosion by over-wash is now not frequent in this zone. The downdrift area ofthe nourishment showed strong erosion (about 15 times thehistorical rate), probably because of the lack of sediment sup-ply because sediment was removed from the low-tide terraceto nourish the dune washovers. Globally, the area experi-enced accumulation during the monitoring period, especiallyduring the second year (Figure 9). The sedimentary balanceis distinct from that expected on the basis of the historicaltrend, partially because of the reduced severity of the 1998–99 winter. The accretion is mainly due to washover nourish-ment and berm development that overcame the seawarddune bluff retreat. The washover infilled areas had relativelyharmonious characteristics in relation to the surroundingnatural dunes. The main distinction was the granulometricdifference. In this area, no vegetation colonization was no-ticed, nor did any aeolian accumulation take place. Preven-tion of erosion and aesthetic considerations with respect totourism were accomplished but ecological recovery did notoccur.

The two types of dune nourishment performed at the Ca-cela Peninsula proved to be successful with respect to theproposed projected objectives. In fact, in both cases, overwashprocesses did not occur and might not occur in the near fu-ture.

On other barrier islands of this system, beach nourishmentwas performed between April 1999 and July 2000, but thesediments were generally eroded at faster rates (DIAS et al.,2003). Dune nourishments, including large volumes of sedi-ments supplied directly to the dune system, might have theadvantage of providing longer life spans than beach nourish-ment because they are not permanently reworked by wavesand tides. However, this kind of protective measure can pro-duce artificial landscapes that might take longer to natural-ize. In places of high tourism pressure, this kind of dune re-covery can have significant economic disadvantages becauseit is not aesthetic, and during placement, the beach cannot

be used. However, these disadvantages are for short time pe-riods; the long-term benefit could overcome these limitations.

In cases in which dune recovery is made by infilling exist-ing breaches, the visual effect is not so pronounced. However,the borrow area should be located outside of the active profilesystem (including all of the dynamically interacting coastalcompartments (i.e., from the back dunes to the beach profileclosure depth).

Dune nourishment designs, where aeolian sediment re-working is possible, appear to be advantageous, with regardto both environmental and economic aspects. The sand trans-port and accumulation on the artificially created dunes is fa-cilitated if a gentle seaward nourishment slope is generated,if the dune position is not prominent in relation to the naturaldynamic equilibrium of the shoreline in the area, and if nour-ished and original sediments are compatible.

ACKNOWLEDGMENTS

The authors acknowledge the Parque Natural da Ria For-mosa for field support, with special mention of Rangers Ar-mando Moura, Carlos Capela, and Silverio Lopes. A specialthanks to everyone from CIACOMAR who were involved infieldwork and laboratory analysis. The authors greatly ac-knowledge Brad Morris for his help with the English revisionof the manuscript.

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