Sediment fluxes and the evolution of a riverine-supplied tectonically-active coastal system: Kyparissiakos Gulf, Ionian Sea (eastern Mediterranean)

Abstract

Kyparissiakos Gulf, located in the southwestern part of Greece (northeastern Ionian Sea), is a riverine-coastal system that has developed over the southern flank of the Alpine orogenic belt (Hellenides). Some 4 km in the vertical separates the heights of the mountain peaks to the depths of the adjacent offshore deep-water basin. This system extends horizontally over approximately 100 km. The area experiences intensive tectonism (e.g. seismicity), a Mediterranean type of climate and microtidal and moderate wave-energy oceanographic settings.Large quantities of sediments (>2.5 x 10 6 t year-l), transferred principally by the River Alfios, are the product of denudation of the high relief (in excess of 2000 m), developed on erodible lithology (with siliciclastics and carbonates >90%) under moderate climatological conditions. The large amounts of sediments produced in the hinterland, in association with land-ocean process interaction, have led to the formation of a coastal zone that includes deltaic plains and coastal barriers with dune fields, which enclose lagoons. The shape and morphological characteristics of the shore zone indicate, clearly: (a) the dominance of the wave activity; (b) an overall northward longshore sediment movement; and (c) a major depocentre at the northern, naturally sheltered, end of the Gulf.Seawards, the coastal zone includes a narrow continental shelf covered with a blanket of recent sediments, which are terrigenous in origin; these extend down a steep slope, where materials is transferred to the deep (approximately 1800 m) offshore basin (the northward component of the Hellenic Trench) primarily by gravitational mass movements; these are triggered often by earthquake activity. To a first approximation, some 50% of the riverine sediment fluxes accumulate over the shelf, whilst another 25% is transported over the slope to the deeper ocean waters.The construction of (two) dams has led to a dramatic reduction in the sediment supply to the coast, having already caused the retreat of the River Alfios deltaic coastline, by >100 m. Similarly, artificial drainage of the lagoons (for the development of agricultural land) has affected the overall ecosystem (altering the the fauna and flora) of the coastal zone Thus, the Upper Quaternary (mostly Holocene) evolution of this particular coastal system is attributed, primarily, to processes and balances between sediment fluxes (e.g. terrestrial transportation, seaward dispersion) and, recently, to human interference.Continental margins are the principal areas of sediment accumulation on Earth. As part of the sedimentation cycle, sedimentary particles are transported from a source to a sink, through a number of processes that include: hill slope erosion; transport by rivers; biological production; temporal storage in an alluvial plain; and, finally, seabed burial. These processes are of major societal importance, as they control natural hazards, pollutant transport, coastal erosion and preservation of

Geomorphology and Sedimentological Processes Along the Coastal Zone Between Livanates and Agios Konstantinos (N. Evoikos Gulf, Central Greece)

“…This nearshore wave climate is associated with a low capability of longshore sediment transport, i.e. the calculated potential annual values are <1200 m 3 /yr (Table 3), when those refer to the open Ionian Sea exceeds 2x10 6 m 3 /yr (Poulos et al, 2002). Along the northern part of the coastal area under investigation, the longshore sediment transport is directed towards the east being more pronounced at its western part (units B and C) and induced mostly by the N and NE windgenerated waves (Fig.…”

Geomorphological characteristics of the sand-dune field of the central Kyparissiakos Gulf

“…2). The incoming waves have formed sub-aqueous oblique welded bars and the net longshore sediment transport in the central part of the gulf is towards the North (Poulos et al 2002).…”

The consequences of a future eustatic sea-level rise on the deltaic coasts of Inner Thermaikos Gulf (Aegean Sea) and Kyparissiakos Gulf (Ionian Sea), Greece

“…The principal morphological, climatological and hydrological characteristics of the river delta systems examined are listed in Table 1. Furthermore, the overall modern evolution of these deltaic coasts has been described: in the case of Thermaikos Gulf, by Kapsimalis et al (2005) and Poulos et al (1994); and, in the case of Kyparissiakos Gulf, by Ghionis and Ferentinos (1992), Ghionis (1993Ghionis ( , 2001 and Poulos et al (2002).…”

“…(b20 cm) environment (Tsimplis, 1994), as with the remainder of the eastern Mediterranean deltas, depends primarily upon interaction between the fluvial (water/sediment fluxes) and the marine (mostly wave activity) processes; the latter are enhanced in the case of wave set-up conditions, which can reach 1 m in the semienclosed Thermaikos Gulf and 0.4 m in the open Kyparissiakos Gulf (Ghionis, 2001;Poulos et al, 2002). The River Axios discharges into the shallow inner Thermaikos Gulf, forming a fluvially-dominated delta, which faces south (Fig.…”

“…The whole delta area has elevations of less than 2 m above m.s.l. and the delta front is retreating, due to sediment deprivation following the construction of a series of hydroelectric dams (Poulos et al, 2002). Between the deltas of the Axios and Aliakmon rivers lies the Loudias-Aliakmon deltaic plain.…”