Coastal Impact of Puebla Farnals Marina (Valencia, Spain)

Coastal impact of Puebla Farnals marina

J. Serra Laboratorio de Puertos y Costas, Universidad Politecnica de

Valencia, 46071 Valencia, Spain

Abstract

Puebla Farnals marina is located on the Spanish Mediterranean coast, between

the "El Puig" hemitombolo and Valencia Port. Therefore Puebla Farnals marina was planned and designed on a coastal area under erosion. The paper reports the effect of the marina development as a littoral barrier, evaluating the damages on downdrift shores.

1 Introduction

The construction of ports upon sandy coasts mean the introduction of barriers

to the littoral drift, that enlarge the beach when windward to the port and cause erosion when leeward. In the Puebla Farnals case, the marina was constructed when coast was already under an erosion process, and therefore increasing erosion.

The paper presents the evolution of the coast line in time, from before and after of the construction. The aim of this paper to establish the effects the marina has on the erosive process on the coast stretch.

2 Localization and characteristics

The Puebla Farnals marina is located in the western Mediterranean sea, situated south of the "El Puig" hemitombolo.

The coast on the marina is located on the natural morphodynamic section, known as "Ovalo Valendano", limited by the delta Ebro, in the north, and the San Antonio cape, in the south (Figue 1), littoral stretch length approximately 270 kilometers. The construction of various ports between the delta and the

292 Marina cape divide the section into smaller sub-sections. Puebla Farnals marina is located halfway between the port of Sagunto in the northern limit and the port of Valencia in the southern limit (Figure 2). The Puebla Farnals marina is classified as a "sea-gained port", its breakwaters start on the coast line and penetrate the sea. The size of the marina being, 850 berths, with a depth of 3 meters in the mouth and between 2 and 3 meters in the basin. The coast between Sagunto and Valencia ports is characterized because of the high number of constructions of coastal and nearshore works, the Sagunto and Valencia ports, the Puebla Farnals and Port-Saplaya marinas, and various coastl work fenders, emphasizing the longshore revetments which protect the A-7 motorway against direct action from the strongs waves.

3 Littoral dynamics

The Puebla Farnals marina is located in the morphodynamic sub-section known as "El Puig", the coast it's characterized by a dune alignment which enclose a line of lagoons, the "El Puig" hemitombolo being the most important features, (Figure 2). The "El Puig" hemitombolo was formed by the Posidonia Oceanica on the sea bed, which protected the shore from wave action therefore provoking sand depositing. The gradual dissappearance of Posidonia Oceanica in recent years has led to an increase of erosion. The most important source of sands in the past was from the rivers Turia and Ebro. The Palancia and Carraixet rivers are currently the only sources of sands. The irregular flow from these rivers, and sporadic flash floods in the region are currently the only source of sands. The littoral drift is Northern-Southerly direction, with a solid transport capacity of between 110.000 and 500.000 mVyear.

The coast between Sagunto and Valencia ports presents a certain stability, with stretches in acretion and others in erosion. The erosion is located South of the barriers of the ports and marinas existing in this littoral stretch and in all the hemitombolo front.

The areas in acretion is located North of the Puebla Farnals and Port- Saplaya marinas, and fundamentally in the beach North of the breakwater of Valencia port, where an estimated mean increase of one meter per year.

4 Coast evolution

Table 1 shows the variations of the coast line between the Puebla Farnals and Port-Saplaya marinas, determined from the photographic restoration of the photogrametric flights of the years : 1947, 1956, 1965, 1972, 1975, 1977 and 1980; the variation values, in meters, are of the coast line in relation to a hypothetic base line of the reference. Figures 3, 4 and 5 shows the variations of the coast line, distinguishing the

Marina 293

time periods before and after of the construction of the marina, and the

comparison between the initial and final situation. Both the table and figures show that erosion was present in all the stretch between 1947 and 1965. Between 1956 and 1965 acretion is seen on the final stretch.

Between 1965 and 1972 erosion is greater in the central and Northen stretch. The marina works are initiated 1967 perhaps being direct cause the increased erosion. The erosion caused in a few years is equivalent to that caused in eigtheen years.

There is a greater erosion in the North due to two factors, firstly the breakwater obstructs the littoral transport and secondly basin starts to accumulate the Southern bound sediements. Therefore, due to a reduction in Southern bound sediments there exists a greater erosion in the South.

The marina extension works are finished in 1974, consisting of an extension of the breakwater parallel to the coast, and a groyn South of the port. The aim of these works is to reduce sedimentation both in the basin and the port mouth. The longshore revetment works are finished in 1974 In this period the

coast has a certanin degree of stability. This construction displaces the erosion to the South. Between 1977 and 1980 Port-Saplaya marina and four coastal protection groyns are built. The groyns have a very irregular effect on the coast. A estable

beach is formed between the first and second and unstable beach but corresponding to counter dynamics is formed between the other groyns. Comparing the period between 1947 and 1980 three areas are distinguishable on the coast. In the North and next to Puebla Farnals marina the

recesion of the coast line is evident, though the erosion it's partially retarded due to the works. In the central zone the erosion it's more greated, and continues on the sumerged beach. This erosion is evident when the waves break over the

rublemond thowing water and stones onto the motorway which is only separate by 30 meters. The last zone South of the beach is in acretion, because of the barrier effect from Valencia port and Port-Saplaya marina. An inflexion point can be seen

where the beach trend is reversed.

5 Conclusions

The coast was already under erosion before the marina construction, but this did accelerate the unstability. The erosion is inmediately seen after the completion of the marina and therefore coastal protection works were carried out.

So as to ro delay the inward coast erosion, longshore revetment is constructed. The beach sands are currently being displaced in a Southern direction and held back by the port of Valencia and Port-Saplaya marina.

294 Marina

To conclude, the marina has contributed to an increase of erosion to the Southern sector of the "El Puig" hemitombolo, therefore requiring coast work fenders.

At present, a regeneration plan of the coast between Puebla Farnals and Port-Saplaya is being carried out to recuperate the beach, tests will be carried out by the construction of long groyns and artificial nourishment to recuperate the beach.

References

Diez, J.J., Esteban, V. & Serra, J. The perfomance of diferent shore protection systems in the east-Spanish Mediterranean coasts, pp. 4119-4131, International Symposium on Maritime Structures in the Mediterranean Sea, Athens, 1984,

National Technical University of Athens.

Estudio de la dindmica litoral en la costa peninsular Mediterranea y Onubense. Direccion General de Puertos y Costas, Ministerio de Obras Publicas y medio

Ambiente, Madrid, 1979

Plan Indicativo de Usos del Medio Litoral. Valencia. Direccion General de Puertos y Costas, Ministerio de Obras Publicas y medio Ambiente, Madrid,

1975

Rosello, V. L'Artificialitzacion del litoral Valencia. Cuadernos de Geografia, n° 38, pp 1-28. Universidad de Valencia, Facultad de Geografia e Historia,

Valencia 1.986

Serra, J. Procesos Litorales de las costas de Caste lion. Tesis Doctoral, Universidad Politecnica de Valencia, Valencia, 1986

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