Summary Within the Gulf of Valencia (Spain), the Ebro Delta and Cullera Bay are presented as ex- amples of coastal fea- tures subject to a range of environmental pres- sures and vulnerable to the impacts of climate change. The Ebro River has ex- perienced an apprecia- ble reduction in flow due to greater freshwa- ter abstraction. Negligible sediment is transported by the river to the delta due to low- er flows and the con- struction of dams. As a consequence, the delta has experienced in- creasing rates of coastal erosion, subsidence and a decline in water qual- ity. Sea-level rise threat- ens to accentuate these environmental prob- lems and could cause salinisation, while an increase in wave storminess would ac- centuate erosion of the coastal fringe. Cullera Bay receives high concentrations of nutrients from the River Júcar and a ma- rine outfall at Cullera and consequently suf- fers from problems of coastal pollution. Warming of sea-water due to climate change could accelerate eu- trophication and fur- ther degrade water quality in the bay with deleterious effects to the natural ecosystem. A rise in sea level could further degrade the en- vironment through salinisation and coastal erosion. 1. The Ebro Delta 1.1 Physical and socio- economic characteristics Geography: The Ebro River (Figure 1) crosses the northeast of Spain with an estimated length of 930 km and a river basin comprising approximately 85,632 km 2 (Mösso et al., 2008), which is about 16% of the surface of Spain. It termi- nates at the Mediterranean Sea, form- ing a delta with the shape of an arrowhead (Figure 2). The delta has two lit- toral spits: the Punta del Fangar to the north and the Trabucador Bar and the Punta de la Banya to the South. The Ebro Delta has an estimated surface of 320 km 2 and is divided by the river into two hemi deltas. Some 77% of the Ebro Delta is used for agriculture while the re- mainder comprises natu- ral areas of beaches, marshes and lagoons. Climate: The region has a Mediterranean climate with temperatures sel- dom higher than 35ºC or lower than 0ºC. The an- nual average tempera- ture is 16.2ºC, with a monthly maximum aver- age of 24.2ºC in August and a minimum of 9ºC in January. The annual aver- BRIEFING NOTES ON THE CIRCE COASTAL CASE STUDIES: THE GULF OF V ALENCIA 1
Transcript
Summary
�Within the Gulf ofValencia (Spain), theEbro Delta and CulleraBay are presented as ex-amples of coastal fea-tures subject to a rangeof environmental pres-sures and vulnerable tothe impacts of climatechange.
�The Ebro River has ex-perienced an apprecia-ble reduction in flowdue to greater freshwa-ter abstraction.Negligible sediment istransported by the riverto the delta due to low-er flows and the con-struction of dams. As aconsequence, the deltahas experienced in-creasing rates of coastalerosion, subsidence anda decline in water qual-ity. Sea-level rise threat-ens to accentuate theseenvironmental prob-lems and could causesalinisation, while anincrease in wavestorminess would ac-centuate erosion of the
coastal fringe.
�Cullera Bay receiveshigh concentrations ofnutrients from theRiver Júcar and a ma-rine outfall at Culleraand consequently suf-fers from problems ofcoastal pollution.Warming of sea-waterdue to climate changecould accelerate eu-trophication and fur-ther degrade waterquality in the bay withdeleterious effects to thenatural ecosystem. Arise in sea level couldfurther degrade the en-vironment throughsalinisation andcoastal erosion.
1. The Ebro Delta
1.1 Physical and socio-economic characteristics
Geography:The Ebro River (Figure 1)crosses the northeast ofSpain with an estimatedlength of 930 km and ariver basin comprising
approximately 85,632 km2
(Mösso et al., 2008),which is about 16% of thesurface of Spain. It termi-nates at theMediterranean Sea, form-ing a delta with the shapeof an arrowhead (Figure2). The delta has two lit-toral spits: the Punta delFangar to the north andthe Trabucador Bar andthe Punta de la Banya tothe South. The Ebro Deltahas an estimated surfaceof 320 km2 and is dividedby the river into two hemideltas. Some 77% of theEbro Delta is used foragriculture while the re-mainder comprises natu-ral areas of beaches,marshes and lagoons.
Climate:The region has aMediterranean climatewith temperatures sel-dom higher than 35ºC orlower than 0ºC. The an-nual average tempera-ture is 16.2ºC, with amonthly maximum aver-age of 24.2ºC in Augustand a minimum of 9ºC inJanuary. The annual aver-
BRIEFING NOTES ON THE CIRCE COASTAL CASE
STUDIES: THE GULF OF VALENCIA
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winds: NE (gregal), E (lle-vant), SW (garbí) and NW(mestral). The prevailingwinds during the sum-mer are from the S and
SW direction, althoughthe strongest winds comefrom the E. In the winter,winds blow more fre-quently from the NW.
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age rainfall is 530 l/m2.
Winds: In the Ebro delta areathere are four prevailing
Figure 1:Location map for
the Gulf of Valencia case studies: The EbroDelta and the Cullera
embayment
Figure 2:The Ebro Delta
Waves: Incident waves on theEbro Delta come fromthree general directions:E-NE, S and NW. Thewave climate of the areahas a well-defined sea-sonal structure withthree stages: A stage oflow energy (June toSeptember) with smallerwave heights and shorterwave periods (S direc-tion); An energetic stage(October to March) withlarger wave heights andlonger wave periods (Eand NW dominate) and;Two stages of transition,one of decreasing energy(April to May) and one ofincreasing energy (at theend of September). In thetransition stages, waveheights have intermedi-ate values and wavespropagate from threemain directions (E, S andNW). The annual averagesignificant wave height(Hs) and mean period(Tz) are 0.75 m and 3.9 srespectively, while themaximum peak period(Tp) during storms has amagnitude of about 11 s.
Tides:Consistent with theMediterranean Sea as awhole (with the exceptionof the northern part of the
Adriatic Sea), the EbroDelta is a microtidal envi-ronment. The maximumrange of the astronomicaltide is 0.25 m, with an av-erage value of 0.16 m(Sierra et al., 2002; 2004).The meteorological tide(storm surge) is a compo-nent as important (oreven more important) asthe astronomical one, andthe maximum sea-levelrise initiated by stormsurges is about 1 m.
River discharge: During the period 1960-90, the annual averagedischarge of the EbroRiver (measured atTortosa, 44 km from theriver mouth) was 424m3/s (Sierra et al., 2002;2004). Mean monthly val-ues show a maximum inFebruary (662 m3/s) and aminimum in August (135m3/s). However, for thelast decade of this period(1980-90) the average val-ues were lower: 300 m3/sfor the annual average;461 m3/s for the monthlyaverage maximum; and119 m3/s for the monthlyaverage minimum. In re-cent years, the Ebro hasexperienced an apprecia-ble reduction in flow, dueto increasing hydraulicexploitation.
Sediment transport: The total amount of sed-iment transported by theEbro River as suspendedload (fine sand) is in theorder of several thou-sand tons per year, butthe washed load (clayand mud) transported isin the order of 100,000 or150,000 tons per year. Incontrast, sedimentretained by river damsranges from 15 to 20 mil-lion tons per year(Palanques and Drake,1987).
1.2 JustificationThe Ebro Delta is a valu-able example of the vul-nerability of deltaic areasof the Mediterranean toclimate change(Sánchez-Arcilla et al.,2007), and the complicat-ed interactions betweensocio-economic pres-sures (abstraction of riverand groundwater foragricultural and domes-tic purposes) (Mösso etal., 2003), environmentalpressures (subsidence,erosion and salinisation),and the consequences ofclimate change (sea-levelrise and wave stormi-ness). A wide range of cli-mate and marine dataare available for the re-gion (Section 2.6) and a
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celerate erosion, a prob-lem compounded bysubsidence of the deltaicbody. Sea-level rise wouldalso affect salinisationthrough the deltaic bodyand river course. Wavestorminess would mainlyaffect erosion of the out-er coastal fringe, andthese effects would befurther compoundedthrough subsidence ofthe deltaic body.
1.4 Key areas of integrationThe following are keyimpact pathways forintegrating impacts ofclimate change in theEbro Delta:
�Sea-level rise and sub-sidence – acceleratedrates of erosion –degradation of coastalfringes and naturalecosystems.
�Sea-level rise and sub-sidence – salinisation –reduction in agricultur-al production and a re-duction in the availabil-ity of drinking water.
�Wave storminess andsubsidence– accelerat-ed rates of erosion –degradation of coastalfringes and naturalecosystems.
1.5 Regional stakeholders,policy makers, institutionsList of end users / stake-holders for the EbroDelta:
�Ebro River Authority( C o n f e d e r a c i ó nHidrográfica del Ebro).
�Institute for theDevelopment of theEbro Region (Institut pelDesenvolupament de lesComarques de l’Ebre).
�Tarragona CoastalBranch, SpanishMinistry of Environ-ment (Demarcación deCostas de Tarragona,Ministerio de MedioAmbiente).
�Regional Ministry ofTerritorial Policy andPublic Works (Departa-ment de Política Territo-rial i Obres Públiques).
�Regional Ministry ofEnvironment andHousing (Departamentde Medi Ambient IHabitatge).
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wide circle of stakehold-ers and decision makershave been established(Section 2.5).
1.3 Key research issuesThe main coastal prob-lems identified for theEbro delta are related toerosion, subsidence, andwater quality. Erosion ofthe delta is largely due tothe reduction of coarsesediment supply fromthe river. Subsidence(lowering of the entiredeltaic area) is largelydue to natural orenhanced compaction(e.g., from the reductionof fine sediment sup-plied by the river, orpumping from ground-water aquifers) and sea-level rise. The river ishighly regulated, thuswater quality is closelyrelated to the variabilityin river discharge. In thefuture, localised torren-tial rain may play animportant role in waterquality. The presentthreats of climate vari-ability identified for theEbro delta are:
i) Sea-level rise
ii) Wave storminess.
Sea-level rise could ac-
1.6 Data availabilityInformation available forthe Ebro Delta:
�Marine climate data:Two wave buoys (CapTortosa and Tarragona)provide observed dataon significant waveheight, maximum waveheight, mean wave pe-riod, maximum peakperiod, wave directionand water temperature(early 1990s onwards).SIMAR-44 data(HIPOCAS project) in-cludes numerical simu-lation of significantwave height, meanwave period, maximumpeak period, wave di-rection, wind velocityand direction and sealevel; 1958-2001.
�Marine water qualitydata from the projectsFANS and PIONEER,include current veloci-ty, nutrients, oxygen,chlorophyll, watertemperature and salin-ity, fluorescence, trans-missivity, suspendedmatter and phyto-plankton concentra-tions; 1996-2000.
�Meteorological data:Three stations in theregion (Deltebre, Portde l’Ampolla, SantCarles de la Rapita)provide observed dataon wind velocity anddirection, air tempera-ture and atmosphericpressure, water tem-perature and sea level;1997 onwards.
�Hydrological data:Daily mean dischargeis available for the EbroRiver for the period1912-2004.
2. Cullera Bay
2.1 Physical and socio-economic characteristics
Geography: Cullera bay and the estu-ary of the Júcar River(Figure 1), located on theSpanish Mediterraneancoast (0º 13’ to 0º 15’ Wand 39º 08’ to 39º 12’ N),comprise a shallow basinwith maximum depths ofaround 10 m (Figure 3).The Cape of Cullera, arocky mass that pro-trudes into the sea, limits
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Figure 3:Location of Cullera Bay
mountain of Cullera actsas a barrier to onshorewinds, causing the windto circle the mountainand funnel through theriver basin. On enteringthe bay, it may bedeflected towards thenorth, enhancing surfacecurrents and transport-ing the freshwater plumetowards the cape (Mössoet al., 2007).
Waves: Cullera Bay is locatedwithin the Gulf ofValencia where the tidalrange is approximately30 cm (spring tide) andhas a limited fetch (theislands of Mallorca,Cabrera and Ibiza areonly 230, 273 and 135 kmeast of the bay).Therefore, tides andwaves have low impor-tance relative to the windfield. The significantwave height exceeds 1 mapproximately 15-17% ofthe time, and exceeds 1.5m only 2-3% of the time(Mösso et al., 2007).
Tides: Consistent with the restof the Mediterranean Sea(with the exception ofthe northern part of theAdriatic Sea), Cullera Bayarea is a microtidal envi-
ronment. The maximumrange of the astronomi-cal tide is 0.3 m. Themeteorological tide(storm surge) has thesame order of magnitudeas the Ebro Delta(Section 1.1).
River discharge: The Júcar River is charac-terised by high concen-trations of nutrients dueto intensive agriculturalexploitation of the river’sdrainage basin, and thedischarge of partiallytreated domestic andindustrial wastewaterfrom towns upstream.River discharge and themarine outfall at Cullera,are the main sources ofnutrient input for thebay. The Júcar River fol-lows a typicalMediterranean pattern,with higher flows fromOctober to May, andlower flows during thesummer months. Meanmonthly discharge variesfrom 4 m3/s in July andAugust to 16 m3/s inFebruary. The velocity atthe river mouth has amean value of 6-7 cm/s.Thus, the influence ofriver momentum to theoverall hydrodynamics ofCullera Bay is negligibleexcept during extreme
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the bay on its northernside, whereas the south-ern end of the bay isopen. It is considered amicro-tidal environ-ment, in which the netriver and marine outfalldischarges display astrong seasonal cycle.The dynamics of the baymainly depend on localsea and weather condi-tions (Mestres et al.,2007, Sierra et al., 2007).During northerly windstorms, the northernpart of this semi-en-closed area becomes se-riously affected by dis-charged detritus fromthe river and marine out-fall. Topographically,Monte el Oro is an im-portant feature of thelandscape north of theJúcar River, while on thesouthern side of the riv-er, the landscape is rela-tively flat.
Winds: The wind field of Cullerabay is highly variable (onthe time scale of hours todays). Onshore winds aremainly from the W, NNWand NW while offshorewinds are mainly fromthe ESE, E and SE.However, the wind fieldinside the bay is far fromhomogeneous. The
flood events (Mösso etal., 2003; 2007).
Sediment transport: Due to extreme pressuresexerted on the JúcarRiver flow, and a weir just2 km upstream of theriver mouth, the amountof sediment transportedby the river is also negli-gible.
2.2 JustificationThe ever-changing envi-ronment of a coastalembayment creates anecological niche that isimportant for seagrass,scallops, soft-shelledclams, and as a breedingground for commerciallyimportant offshore fish.Coastal bays are also ofmajor importance asrecreational areas.However, Cullera Bay is atypical example of amulti-source pollutedcoastal environment(Sierra et al, 2007). Itreceives the discharge ofthe Júcar River and of ashallow marine outfall.Agriculture and industryexert environmentalpressure on the riverbasin which in turnaffects the water qualityof the bay. Abstraction offreshwater, which is laterreturned to the river
loaded with pesticidesand fertilizers, and dis-charge of partially treat-ed wastewater fromriverbank towns andindustries into the lowerreaches of the river, aresome of the mechanismsthat contribute to riverpollution. These envi-ronmental pressuresincrease the vulnerabili-ty of the region toimpacts of climatechange such as sea-levelrise and ocean warming.
2.3 Key research issuesThe dual threats of cli-matic variability identi-fied for this regioninclude warming of seatemperatures and anincrease in mean sealevel. Warmer tempera-tures would enhanceeutrophication and inturn further degradewater quality. Sea-levelrise would affect riverdischarge and salinisa-tion, similar to thepotential impacts out-lined for the Ebro Deltacase study.The main issues identi-fied for this coastalembayment are relatedto water quality and ero-sion. The chief problemis one of water quality.The high influx of
tourists and visitors (by afactor of 5-10) in thesummer season con-tributes significantly tothe coastal economy butmay be negativelyimpacted by the prob-lems of water quality inthe bay and by coastalerosion.
2.4 Key areas of integration�Increasing sea temper-
ature (and nutrient en-richment by industry /agriculture / settle-ment) – eutrophication– decline in water qual-ity – negative impacton tourism / fishing in-dustry.
2.5 Regional stakeholders,policy makers, institutionsStakeholders for CulleraBay include:
�Valencia CoastalBranch, SpanishMinistry of Environ-ment (Demarcación deCostas de Valencia,Ministerio de MedioAmbiente).
�Júcar River Authority
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riod, maximum peakperiod, wave direction,wind velocity and di-rection and sea level;1958-2001.
�Water quality data(ECOSUD projects): in-cluding nutrients,chlorophyll, water tem-perature and salinity,suspended matter andphytoplankton con-centrations. Data fromdifferent cruises be-tween 2002 and 2003.
�Tidal gauge (Valencia):Sea level, 1992-2007.
�Júcar River discharge(Cullera): Total monthlydischarge, 1911-1997.
Acknowledgements
CIRCE (Climate Changeand Impact Research:the MediterraneanEnvironment) is fundedby the Commission ofthe European Union(Contract No 036961GOCE) http://www.cir-ceproject.eu/. This brief-ing note forms part of theCIRCE deliverableD11.5.1.
�Final version, January 2008
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( C o n f e d e r a c i ó nHidrográfica del Júcar).
�Regional Ministry ofAgriculture, Fisheriesand Nourishment(Consellería de Agri-cultura, Pesca y Ali-mentación).
�Regional Ministry ofTerritory and Housing(Consellería de Terri-torio y Vivienda).
�Regional Ministry ofEnterprise, Universityand Science (Consell-ería de Empresa,Universidad y Ciencia).
�Municipality of Cullera(Ayuntamiento deCullera).
2.6 Data availabilityAvailable meteorological,marine and hydrologicaldata for Cullera Bay:
�Wave buoy (Valencia):Data on significantwave height, maximumwave height, and meanwave period, 1985-2005.
References:�Mösso, C., Mestres, M., Sánchez-Arcilla, A., Sierra, J. P., González del Río, J., Rodilla, M.
& López, F. (2003). River plume behaviour in the Spanish Mediterranean Coast.Hydromorphodynamic controls. Proc. 3rd IAHR Symposium on River, Coastal andEstuarine Morphdynamics, pp 935-945. �Mösso, C., Sierra, J. P., Mestres, M., Cupul, L., Falco, S., Rodilla, M., Sánchez-Arcilla, A.
& González del Río, J. (2007). The influence of topography on wind-induced hydrody-namics in Cullera Bay. Journal of Coastal Research (ISSN: 0214-8358), Special Issue 47pp 16-29.�Mösso, C., Sierra, J.P., Rodilla, M., Romero, I., Falco, S., González del Río, J and
Sánchez-Arcilla, A. (2008). High Vertical Resolution Sampling in Density Interfaces ofEstuaries and River Plumes. Estuaries and Coasts, In Press.�Palanques, A. and Drake, D.E. (1987). Distribution des suspensions sur le plateau du
delta de l’Ebre. Colloq. Int. Océanologie, Ecosystèmes de Marges Continentales, CIESM,Perpignan, 23 pp.�Sánchez-Arcilla, A., Jiménez, José A. and Valdemoro, H. (2007). The Vulnerability and
Sustainability of Deltaic Coasts: The Case of the Ebro Delta, Spain. Managing CoastalVulnerability. Loraine McFadden, Robert J. Nicholls and Edmund Penning-Roswell(editors), Elseiver. 79-95 pp.�Sierra, J. P., Sánchez-Arcilla, A., González del Río, J., Flos, J., Movellán, E., Mösso, C.,
Martínez, R., Rodilla, M., Falco, S. & Romero, I. (2002). Spatial distribution of nutrientsin the Ebro estuary and plume. Continental Shelf Research (ISSN: 0278-4343), Vol 22(2) pp 361-378.�Sierra, J. P., Sánchez-Arcilla, A., Figueras, P. A., González del Río, J., Rassmusen, E. K. &
Mösso, C. (2004). Effects of discharge reductions on salt wedge dynamics of the Ebroriver. River Research and Applications (ISSN: 1535-1459), Vol 20 (1) pp 61-77.�Sierra, J. P., Mösso, C., González del Río, J., Mestres, M., Cupul, L., Sánchez-Arcilla, A.,
Rodilla, M., Falco, S., Romero, I., González, D. & Puigdefábregas, J. (2007). Sources andsinks of nutrients and pollutants in Cullera Bay. Journal of Coastal Research (ISSN:0214-8358), Special Issue 47 pp 30-38.
