Cost of beach maintenance in the Gulf of Cadiz (SW Spain)

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<ul><li><p> .Coastal Engineering 42 2001 143153www.elsevier.comrlocatercoastaleng</p><p> /Cost of beach maintenance in the Gulf of Cadiz SW SpainJuan J. Munoz-Perez a,), Belen Lopez de San Roman-Blanco b, </p><p>Jose M. Gutierrez-Mas c, Luis Moreno d, Gabriel J. Cuena ea Demarcacion de Costas en Andalucia-Atlantico, Ministerio de Medio Ambiente, cr Marianista Cubillo, 7, 11071 Cadiz, Spain</p><p>b Coastal Department, HR Wallingford, Howbery Park, Wallingford OX10 8BA, UKc Facultad de Ciencias del Mar, Uni. de Cadiz. CASEM, 11540, Puerto Real, Spain</p><p>d Ministry of Enironmental Protection, Pza. San Juan de la Cruz, srno.-28071 Madrid Spaine Sericio de Costas de Huela, Cr Rico, 15 21071, Huela, Spain</p><p>Received 3 February 2000; received in revised form 16 August 2000; accepted 7 September 2000</p><p>Abstract</p><p>Beach erosion problems have been solved by adding sand to the beaches along the Gulf of Cadiz. The Gulf is located inSW Spain between the Portuguese border and the Strait of Gibraltar. During the last decade, more than 12=106 m3 of sandhave been nourished in 38 restoration operations carried out on 28 beaches. The main characteristics of the nourishment</p><p> .campaigns year, volume, budget, transport method, sand data, etc. are presented. Location of sand borrow sites anddistance to the beaches are also shown. Monitoring programs have been performed in order to calculate sediment loss rates.These results have been related to the beach length, the berm width and the budget in order to obtain a variety ofrelationships for maintenance cost as, for example, the total annual cost for each beach. This information is very useful whendeveloping a strategy in coastal zone management. Furthermore, at least in reef-protected beaches, small yearly renourish-ments similar to the yearly losses, instead of greater nourishments performed with a periodicity of many years, lead to aneconomical saving, as well as to a better use of the natural resources. q 2001 Elsevier Science B.V. All rights reserved.</p><p>Keywords: Beach nourishment; Coastal zone management; Beach erosion; Gulf of Cadiz</p><p>1. Introduction</p><p>The coastline of the Gulf of Cadiz has been inrecession for at least the last century. Subsidencephenomena, sea level rise or manmade barriers, asgroin constructions like the breakwater built in thePortuguese bank of the Guadiana River mouth, arethe causes.</p><p>) Corresponding author. Fax: q34-56-276-449. .E-mail address: juanjose.munoz@uca.es J.J. Munoz-Perez .</p><p>Analysis of field data and aerial photographs overthe last half century show that the coastline hassuffered a recession rate of approximately 1 mryearin some points of the Spanish Southwest Atlantic</p><p> .coast Munoz-Perez and Enriquez, 1998 .Because ofthe erosion, the Spanish Coastal Authority, in thepast dependent upon the Ministry of Public Worksand presently belonging to the Ministry of the Envi-ronmental Protection, decided to begin a coastalprotection program.</p><p>Erosion is caused by a negative sediment budgetand, at the present, adding sand to the physiographic</p><p>0378-3839r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. .PII: S0378-3839 00 00054-5</p></li><li><p>( )J.J. Munoz-Perez et al.rCoastal Engineering 42 2001 143153144</p><p>unit appears to be the most natural way to solve theerosion problem. Some beach nourishment projectshave sometimes been complemented with the con-struction of some permeable and short groins ad-justed to the beach profile. This was only carried outwhen an important reduction of the annual nourish-</p><p>ment requirement justified it Munoz-Perez and.Gutierrez-Mas, 1999 .</p><p>Monitoring the behaviour of several beaches sincethe first nourishment allowed for a comparison withprevious works, as well as to establish real meanrates of erosion for each job and predict renourish-ment requirements in the future. Other countrieshave been monitoring for a much greater length of</p><p>time see amongst others, Wijnberg, 1995; Lin and.Sasso, 1996; Shak and Ryan, 1996 , and compila-</p><p>tions of information on this topic have also beenperformed. For instance, a database that documentsbeach nourishment episodes, which have occurred on</p><p> .the US Eastern shoreline from New York to Florida .was presented recently by Valverde et al. 1999 .</p><p>Also, the economic importance of beaches and their .tourism has been examined by Houston 1995, 1996 .</p><p>The federal spendings for shoreline preservation andthe revenues for the government and benefits for the</p><p> .national economy have been compared King, 1999 .Nevertheless, the yearly cost of the different beachnourishment programs is a little published parameteryet. The range of this value could prove to be veryinteresting in providing a better design tool for futurenourishment projects and to decide whether theyshould be carried out or not.</p><p>The main aim of this paper is to describe amorphological and economical evaluation of thebeach nourishment maintenance strategy carried outin the Gulf of Cadiz during the 1990s.</p><p>2. Data compilation</p><p>The coastline which is to be studied is locatedalong the Gulf of Cadiz, facing the Atlantic Oceanon the southwest coast of Spain, between the Guadi-ana River mouth and the Strait of Gibraltar. Ageneral view of the area and the location of the 28beaches, where the 38 nourishments were carriedout, are presented in Fig. 1. The region has a mesoti-dal range with a medium neap to spring variation</p><p> .1.203.30 m . Most of the beaches are composed of .fine-medium sand D s250 mm consisting of50</p><p>8595% quartz and 515% calcium carbonate. Inmany beaches, the typical profiles intersect a sub-merged reef and, consequently, are not sand rich.Wave decay due to the wave breaking over thesubmerged reef, the changes on the resulting beachprofile shape and the stability of the beach were</p><p> .discussed by Munoz-Perez et al. 1999a .Wave climate data have been collected by two</p><p>waverider buoys included in the Spanish Wave .Recording Network known as REMRO . The first</p><p>of these buoys, named ASevilleB, was installed infront of the Guadalquivir river mouth anchored at adepth of y12 m. The second one, named ACadizB,was anchored at a depth of y22 m, 3 miles seawardfrom a rocky shoal in front of the city of Cadiz.Statistically elaborated data are available in the Mar-itime Works Recommendations ROM 0.391 .MOPT, 1991 .</p><p>Geophysical campaigns have been performed overthe entire width of the coast in order to identify</p><p>submerged borrow sand areas Esgemar, 1991; Ge-.omytsa, 1991a,b, 1994 . Soundings of the sea bottom</p><p>were carried out to check the thickness of sedimentdeposits. Location of borrow sites and dredged vol-umes are shown in Fig. 2. A large number of surfacegrab sediment samples were also collected to iden-tify the borrow sand characteristics.</p><p>A conventional topographic surveying techniquewas employed in the aerial part of the beach. Adifferential leveling with reference to a benchmarklocated in the seaside promenade was performed atthe hour of the spring low tide. It was possible tosurvey up to elevation y1.00 m. Due to the fact thatbathymetric contours were made with an echosounderon boat and differential global position system .DGPS at the spring high tide, an area of overlapwith the aerial topography relates both surveys to thesame datum or Azero levelB. For a comprehensivedescription about the accuracy of the method, see</p><p> .Munoz-Perez 1995 . The total cost of the monitor-ing works was US$450,000 during the last decade,only 1.2% of the beach restoration investments.</p><p>Currents were also measured. The final aim ofthese measurements being the calibration of themathematical models developed to study differentaspects of the coastline evolution.</p></li><li><p>()</p><p>J.J.Munoz-Perez</p><p>etal.r</p><p>CoastalEngineering42</p><p>2001143</p><p>153</p><p>145</p><p>Fig. 1. Location of the 28 beaches renourished in the decade 19891998.</p></li><li><p>( )J.J. Munoz-Perez et al.rCoastal Engineering 42 2001 143153146</p><p>Fig.</p><p>2.Lo</p><p>catio</p><p>noft</p><p>hesa</p><p>nd</p><p>borro</p><p>wsit</p><p>esin</p><p>the</p><p>Gul</p><p>fofC</p><p>adiz</p><p>.</p></li><li><p>( )J.J. Munoz-Perez et al.rCoastal Engineering 42 2001 143153 147</p><p>Once the beach restoration was finished, newbathymetric surveys were carried out in the majorityof cases. These were performed once per year for, atleast, a period of 2 years. Hence, profile comparisonscould be made and erosion rates estimated.</p><p>3. Results and discussion</p><p>Data collected for the 38 beach nourishmentsperformed during the last decade are presented inTable 1. From left to right, the data specified are thefollowing.</p><p>v .Date year and name of the beach whererestoration works were carried out. Successiverestorations performed on the same beach are shownby different ordinal numbers. So, Fuentebravia,Fuentebravia II and Fuentebravia III would note thefirst, second and third nourishment projects. Therewere 38 sand-pouring operations accomplished on 28beaches from 1989 to 1998.</p><p>v Volume of sand poured in the nourishment,which was generally surveyed in the hopper and isexpressed in cubic meters. Total volume was 12.0=</p><p>6 3 10 m with a maximum in Victoria Beach 2.0=6 3.10 m .v Final budget, in US$, where Spanish taxes as</p><p> .16% value added tax VAT are not included andcost of hard structures such as groins, when neces-sary, are not considered. All costs were adjusted forSpanish inflation factors and converted to 1999 dol-lars. Global investment was US$37.5=106, that isUS$3.7=106ryear.</p><p>v Transport method ground transport by trucks or.maritime dredging by trail suction is specified.</p><p>Ground transport by trucks, from adjacent beaches ordunes, was performed to nourish 13 beaches. Thevolume transported was 6.5% of the total volume,while the cost was only the 5.5% with an averagevalue of US$2.7rm3. Distances vary from 0.4 to11.2 km with 4.2 km as the average value. On theother hand, volume dredged had an average cost ofUS$3.1rm3 and an averaged distance of 10.9 kmwithin a range from 0.5 to 35 km.</p><p>v The main characteristics of the sediment arealso presented. It refers to the mean diameter, inmicrons, of the borrow sand which is very similar to</p><p>the native one. Three different areas can be distin-guished along the coastline according to the grainsize. The western one, between Guadiana andGuadalquivir rivers, has a median grain size diameterwhich varies from 350 to 670 mm with an averagevalue of 450 mm. Sand size is finer betweenGuadalquivir river and the Strait of Gibraltar: D s50280 mm. A coarser grain size of 1000 mm is presentin Guadalquiton beach, in the Mediterranean Sea.Weight of the siltclay fraction is negligible, about1.6%. The percentage of the bioclastic fraction, i.e.the part composed of flat shell fragments which are,</p><p>usually, very quickly transported seawards Munoz-.Perez et al., 1999b , is also indicated. This value</p><p>varies extensively, from 3% to 32% with an averageof 12.9%.</p><p>v The type of profile is specified: reef supportedor sand rich.</p><p>v Location of the borrow site submerged or. .emerged and distance kilometer from the borrow</p><p>area to the beach nourishment.Working with the previously described character-</p><p>istics and along with the beach dimension, a new setof parameters related to the maintenance manage-ment are developed. These values presented in Table2 are as follows.</p><p>v The erosion rate is computed by averaging thelosses after nourishments and based on total beachprofile measurements, throughout a monitoring pe-riod of at least two years. It is expressed in cubicmeters per year. These data are not specified in 14nourishment operations because no monitoring workswere performed.</p><p>v Length of the beach where restoration workswere carried out and berm width achieved with thenourishment. Both of these values are expressed inmeters. The block diagram shown in Fig. 3 clarifiesthe meaning of beach length and berm width.</p><p>v Sediment loss per year per longitudinal meter,obtained by dividing the yearly erosion rate by thebeach length. Average value is 37.5 m3rmryear.Greatest values correspond to Aculadero, Fuente-</p><p>bravia and La Pena beaches 58, 90 and 1083 .m rmryear, respectively .</p><p>v3 .Unit cost of sand US$rm , id est, the relation-</p><p>ship between the real total budget and the fill volumeof the nourishment. The average value is aboutUS$3rm3 with a maximum of US$6.7rm3.</p></li><li><p>( )J.J. Munoz-Perez et al.rCoastal Engineering 42 2001 143153148</p><p>Tabl</p><p>e1</p><p>Bea</p><p>chnouris</p><p>hmen</p><p>tin</p><p>the</p><p>Gulf</p><p>of</p><p>Cadi</p><p>zin</p><p>the</p><p>last</p><p>deca</p><p>de</p><p>.Y</p><p>ear</p><p>Beach</p><p>nam</p><p>eV</p><p>olu</p><p>me</p><p>Tota</p><p>lbud</p><p>get</p><p>Tran</p><p>spor</p><p>tSa</p><p>nd</p><p>Kin</p><p>do</p><p>fpro</p><p>file</p><p>Bo</p><p>rro</p><p>ware</p><p>aD</p><p>ista</p><p>nce</p><p>km3</p><p>.</p><p>.</p><p>mU</p><p>S$m</p><p>eth</p><p>odD</p><p>Perc</p><p>en</p><p>tPe</p><p>rcen</p><p>tsh</p><p>ell</p><p>50</p><p>.m</p><p>msi</p><p>ltfr</p><p>actio</p><p>n</p><p>1989</p><p>Cast</p><p>illa</p><p>Beach</p><p>1,69</p><p>0,00</p><p>03,</p><p>813,</p><p>333</p><p>Trail</p><p>suctio</p><p>n60</p><p>01.</p><p>5Sa</p><p>nd</p><p>rich</p><p>Pon</p><p>ien</p><p>tejet</p><p>ty6.</p><p>319</p><p>90La</p><p>An</p><p>tilla</p><p>1,30</p><p>0,00</p><p>05,</p><p>333,</p><p>000</p><p>Trail</p><p>suctio</p><p>n50</p><p>01.</p><p>3Sa</p><p>ndric</p><p>hR</p><p>om</p><p>pidi</p><p>llosp</p><p>it6.</p><p>119</p><p>90La</p><p>Cachu</p><p>cha</p><p>82,0</p><p>3050</p><p>5,40</p><p>6Tr</p><p>ucks</p><p>300</p><p>2.6</p><p>8Sa</p><p>nd</p><p>rich</p><p>San</p><p>Pedr</p><p>om</p><p>ou</p><p>th3.</p><p>819</p><p>91La</p><p>Cale</p><p>ta41</p><p>,440</p><p>81,0</p><p>32Tr</p><p>ucks</p><p>310</p><p>3.6</p><p>3R</p><p>eefs</p><p>upp</p><p>orte</p><p>dC</p><p>ort</p><p>adu</p><p>rabe</p><p>ach</p><p>1.4</p><p>1991</p><p>Vic</p><p>toria</p><p>2,00</p><p>0,05</p><p>05,</p><p>527,</p><p>742</p><p>Trail</p><p>suctio</p><p>n25</p><p>02.</p><p>411</p><p>Sand</p><p>rich</p><p>an</p><p>dC</p><p>adi</p><p>zC</p><p>han</p><p>nel</p><p>5.2</p><p>reefs</p><p>upp</p><p>orte</p><p>d19</p><p>91St</p><p>a.</p><p>Maria</p><p>delM</p><p>ar</p><p>306,</p><p>360</p><p>557,</p><p>419</p><p>Trail</p><p>suctio</p><p>n35</p><p>01.</p><p>516</p><p>Reefs</p><p>upp</p><p>orte</p><p>dC</p><p>adi</p><p>zH</p><p>arb</p><p>ou</p><p>ren</p><p>tran</p><p>ce</p><p>6.0</p><p>1991</p><p>LaPe</p><p>na67</p><p>,035</p><p>216,</p><p>774</p><p>Tru</p><p>cks</p><p>230</p><p>1.2</p><p>29R</p><p>eefs</p><p>upp</p><p>orte</p><p>dV</p><p>ald</p><p>evaq</p><p>uero</p><p>sdu</p><p>ne11</p><p>.2</p><p>1991</p><p>Can</p><p>osde</p><p>Meca</p><p>16,1</p><p>0339</p><p>,914</p><p>Truc</p><p>ks23</p><p>01.</p><p>710</p><p>Ree</p><p>fsupp</p><p>orte</p><p>dTr</p><p>afal</p><p>gard</p><p>une</p><p>2.4</p><p>1991</p><p>Ro</p><p>San</p><p>Pedr</p><p>o23</p><p>,159</p><p>59,6</p><p>49Tr</p><p>ails</p><p>uctio</p><p>n22</p><p>01</p><p>15R</p><p>eefs</p><p>upp</p><p>orte</p><p>dSa</p><p>nPe</p><p>dro</p><p>mouth</p><p>0.5</p><p>1992</p><p>Reg</p><p>la50</p><p>2,00</p><p>02,</p><p>650,</p><p>000</p><p>Trai</p><p>lsuctio</p><p>n25</p><p>02.</p><p>58</p><p>Reefs</p><p>upp</p><p>orte</p><p>dPl</p><p>acer</p><p>San</p><p>Jaci</p><p>nto</p><p>4.2</p><p>1992</p><p>Can</p><p>osde</p><p>Meca</p><p>II12</p><p>4,23</p><p>426</p><p>3,61</p><p>9Tr</p><p>ucks</p><p>230</p><p>1.5</p><p>12R</p><p>eefs</p><p>upp</p><p>orte</p><p>dTr</p><p>afal</p><p>garD</p><p>une</p><p>2.4</p><p>1992</p><p>Fuen</p><p>tebr</p><p>avia</p><p>75,0</p><p>0021</p><p>2,74</p><p>8Tr</p><p>ucks</p><p>390</p><p>0.3</p><p>9R</p><p>eefs</p><p>upp</p><p>orte</p><p>dR</p><p>ota</p><p>Har</p><p>bour</p><p>0.9</p><p>1993</p><p>Car</p><p>men</p><p>23,1</p><p>5043</p><p>,413</p><p>Truc</p><p>ks22</p><p>00.</p><p>515</p><p>Sand</p><p>rich</p><p>Bar</p><p>bate</p><p>Har</p><p>bour</p><p>0.6</p><p>1993</p><p>Poni</p><p>ente</p><p>131,</p><p>819</p><p>187,</p><p>062</p><p>Truc</p><p>ks39</p><p>00.</p><p>38</p><p>Sand</p><p>rich</p><p>Atu</p><p>nara</p><p>beac</p><p>h6.</p><p>719</p><p>93El</p><p>Palm</p><p>ar18</p><p>,794</p><p>33,7</p><p>27Tr</p><p>ucks</p><p>250</p><p>1.2</p><p>12Sa</p><p>ndric</p><p>hC</p><p>onile</p><p>tem</p><p>outh</p><p>2.0</p><p>1993</p><p>LaPe</p><p>naII</p><p>170,</p><p>000</p><p>413,</p><p>641</p><p>Truc</p><p>ks24</p><p>01</p><p>31R</p><p>eefs</p><p>upp</p><p>orte</p><p>dV</p><p>alde</p><p>vaqu</p><p>eros</p><p>dune</p><p>11.2</p><p>1993</p><p>19</p><p>94La</p><p>Barr</p><p>osa</p><p>463,</p><p>607</p><p>1,24</p><p>2,56</p><p>4Tr</p><p>ails</p><p>uctio</p><p>n29</p><p>03.</p><p>415</p><p>Sand</p><p>rich</p><p>Plac</p><p>erde</p><p>Mec</p><p>a25</p><p>.119</p><p>94Fu</p><p>ente</p><p>brav</p><p>aII</p><p>275,</p><p>133</p><p>540,</p><p>733</p><p>Trai</p><p>lsuctio</p><p>n28</p><p>02.</p><p>512</p><p>Ree</p><p>fsupp</p><p>orte</p><p>dC</p><p>adiz</p><p>Cha</p><p>nnel</p><p>8.1</p><p>1993</p><p>19</p><p>94El</p><p>Acula</p><p>dero</p><p>172,</p><p>448</p><p>267,</p><p>613</p><p>Trai</p><p>lsuctio</p><p>n39</p><p>00.</p><p>517</p><p>Ree</p><p>fsupp</p><p>orte</p><p>dC</p><p>adiz</p><p>Cha</p><p>nnel</p><p>4.5</p><p>and</p><p>truc</p><p>ks19</p><p>94La</p><p>Hie</p><p>rbab</p><p>uena</p><p>16,2</p><p>1640</p><p>,516</p><p>Truc</p><p>ks22</p><p>00.</p><p>812</p><p>Sand</p><p>rich</p><p>Bar</p><p>bate</p><p>Har</p><p>bour</p><p>0.4</p><p>1994</p><p>Can</p><p>osde</p><p>Meca</p><p>III</p><p>496,</p><p>000</p><p>1,02</p><p>1,93</p><p>6Tr</p><p>ails</p><p>uctio</p><p>n30</p><p>03.</p><p>514</p><p>Ree</p><p>fsupp</p><p>orte</p><p>dPl</p><p>acer</p><p>deM</p><p>eca</p><p>4.0</p><p>1994</p><p>Fuen</p><p>tede</p><p>lGal</p><p>lo39</p><p>9,00</p><p>01,</p><p>037,</p><p>419</p><p>Trai</p><p>lsuctio</p><p>n23</p><p>02</p><p>18R</p><p>eefs</p><p>upp</p><p>orte</p><p>dPl</p><p>acer</p><p>deM</p><p>eca</p><p>13.0</p><p>1994</p><p>Isla</p><p>Cris</p><p>tina</p><p>330,</p><p>000</p><p>887,</p><p>000</p><p>Trai</p><p>lsuctio</p><p>n35</p><p>01.</p><p>3Sa</p><p>ndric</p><p>hIs</p><p>laC</p><p>ristin</p><p>aH</p><p>arb</p><p>our</p><p>4.1</p><p>1995</p><p>LaB</p><p>ota</p><p>930,</p><p>000</p><p>3,18</p><p>7,00</p><p>0Tr</p><p>ails</p><p>uctio</p><p>n67</p><p>01.</p><p>5-</p><p>20Sa</p><p>ndric</p><p>hPo</p><p>nien</p><p>teD</p><p>ique</p><p>13Ju</p><p>an</p><p>Carlo</p><p>sI</p><p>1995</p><p>Chi</p><p>ca</p><p>12,7</p><p>7840</p><p>,516</p><p>Tru</p><p>cks</p><p>230</p><p>1.5</p><p>32R</p><p>eefs</p><p>upp</p><p>orte</p><p>dV</p><p>ald</p><p>evaq</p><p>uero</p><p>sD</p><p>un</p><p>e11</p><p>.219</p><p>95El</p><p>Ro</p><p>mpi</p><p>dillo</p><p>7,73</p><p>511</p><p>,581</p><p>Tru</p><p>cks</p><p>220</p><p>111</p><p>Reefs</p><p>upp</p><p>orte</p><p>dR</p><p>ota</p><p>Harb</p><p>our</p><p>0.6</p><p>1996</p><p>LaC</p><p>ost</p><p>illa</p><p>197,</p><p>000</p><p>948,</p><p>746</p><p>Trail</p><p>suctio</p><p>n38</p><p>03</p><p>9Sa</p><p>nd</p><p>rich</p><p>Cadi</p><p>zC</p><p>han</p><p>nel</p><p>11.0</p><p>1996</p><p>Acu</p><p>lade</p><p>roII</p><p>75,6</p><p>2524</p><p>0,94</p><p>6Tr</p><p>ail</p><p>suctio</p><p>n25</p><p>03.</p><p>514</p><p>Reefs</p><p>upp</p><p>orte</p><p>dC</p><p>adi</p><p>zC</p><p>han</p><p>nel</p><p>4.5</p><p>1996</p><p>LaC</p><p>ost</p><p>illa</p><p>II94</p><p>,566</p><p>292,</p><p>351</p><p>Trail</p><p>suctio</p><p>n35</p><p>01.</p><p>28</p><p>San</p><p>dric</p><p>hC</p><p>adi</p><p>zC</p><p>han</p><p>nel</p><p>11.0</p><p>1996</p><p>Fuen</p><p>tebr</p><p>av</p><p>aII</p><p>I13</p><p>4,80</p><p>835</p><p>1,67</p><p>5Tr</p><p>ail</p><p>suctio</p><p>n30</p><p>03</p><p>11R</p><p>eefs</p><p>upp</p><p>orte</p><p>dC</p><p>adi</p><p>zC</p><p>han</p><p>nel</p><p>8.1</p><p>1996</p><p>Maz</p><p>agon</p><p>425,</p><p>000</p><p>1,40</p><p>6,36</p><p>4