Difference between revisions of "Greek case studies: Morphological evolution of the R.Alfios deltaic shoreline"

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Therianos A.D., 1974 The geographical distribution of the river water supply in Greece. Bulletin Geological Society, Greece, 11, 28-58 (in Greek).
 
Therianos A.D., 1974 The geographical distribution of the river water supply in Greece. Bulletin Geological Society, Greece, 11, 28-58 (in Greek).
  
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|AuthorID1=13543  
 
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|AuthorName1= Ghionis, George
 
|AuthorName1= Ghionis, George

Revision as of 14:42, 3 August 2011


Examples of Morphological Changes

Case Study 1: Morphological evolution of the R. Alfios deltaic shoreline by G.Ghionis and S. Poulos 2005.

The mouth area of the R. Alfios located at the northern part of the Kyparissiakos Gulf, which lies along the west coast of Peloponnese, facing to the NE Ionian Sea. The catchment area of the R. Alfios covers an area of some 3665 km2, being mountainous with elevations exceeding 2200 m.

Figure 3. The mouth area of R. Alfios (NW Peloponnese, Ionian Sea) Topgraphic map published by the Hellenic Army Geographical Service, in 1972.)

Fluvial water and sediment fluxes are rather high, with mean annual discharge in the order of 67 m3/s (maximum=145 m3/s) (Therianos, 1974) whilst during flood events discharges oftenly exceed the 1000 m3/s. In accordance to high amounts of water discharge, the temperate type of climate, the relatively erodible lithology (Quaternary deposits + flysch ~52%), and the mountainous relief, the amounts of sedimentary material available for transport by the river network are expected also to be significant. Although, no direct measurements exist for the sediment fluxes of the R. Alfios, on the basis of monthly suspended sediment flux data available for other Greek rivers discharging into the Ionian Sea i.e . R. Acheloos (2.5x106 t), R Arachthos (7.3x106 t), R. Kalamas (1.9x106 t) and published information regarding sediment fluxes in the northeastern Mediterranean Sea (e.g. Poulos & Collins, 2002) an amount of some 2.5x106 tonnes per year of suspended sediment (i.e. SSL) and more than 3x106 tonnes of total sediment load are expected to be transported towards its deltaic coast by the R. Alfios, annually(Poulos et al., 2002). The delta is exposed primarily to wind-induced waves approaching from the S, SW and W and NW involving due to very long (hundreds of km) fetches a wave regime with wave heights >5 m, during storms and a potential longshore northward sediment transport in front of the river mouth in the order of 0.5 106 m3/yr (Ghionis et al., 2005). Over the last decades the major human interference to the natural deltaic evolution was the construction of the Ladona and Floka dams; the former is a gravity-type of dam producing 750.000 Volt of electric power, whilst the latter is an irrigation dam, that establishes a steady flow of fresh water of approximately 40 m3/hr, throughout the year. The Ladonas dam got in operation in 1955 cutting off an upstream area of some 900 km2, which represents the 25% of the total drainage basin. The second dam (Flokas), put in operation in 1967, being only 6 km away from the coastline and having upstream of it the 97% of the catchment, have reduced drastically the sediment fluxes, at least those related to that transported as bed load and most of the suspended sediment load. The consequences on the deltaic evolution, as revealed from the comparison of aerial photographs, incorporate a relatively rapid and spatially important shoreline retreat (see Fig. 4), which in the river mouth exceeds 300 m becoming smaller to the north and south but not being insignificant for distances larger than a few km.

Figure 4. Shoreline retreat of the Mouth area of R. Alfios following the construction of dams (Ghionis et al., 2005)

Bibliography sited

Ghionis G., Poulos S.E., Gialouris P. & Gianopoulos Th., 2005. Recent morphological evolution of the deltaic coast of R. Alfios due to natural processes and human impact. Proceedings of the 7th Panehellenic Geographical Congress, Mytilini, Oct. 2004, v.1, p.302-308 (in Greek)

Poulos S.E. and Collins M.B., 2002. Fluvatile sediment fluxes to the Mediterranean Sea: a quantitative approach and the influence of dams. In: S.J Jones.and L.E Frostick (eds),. Sediment Flux to Basins: Causes Controls and Consequences. Geological Society of London Special Publications, 191, 227-245.

Poulos S.E., Voulgaris G., Kapsimalis V., Collins M. and Evans G., 2002. Sediment fluxes and the evolution of a riverine-supplied tectonically-active coastal system: Kyparissiakos Gulf, Ionian Sea (eastern Mediterranean). (In:) Jones S.J. & Frostick L.E. (eds) Sediment Flux to Basins: Causes, Controls and Consequences. Geological Society, London, Special Publications, 191, 247-266.

Therianos A.D., 1974 The geographical distribution of the river water supply in Greece. Bulletin Geological Society, Greece, 11, 28-58 (in Greek).

The main authors of this article are Ghionis, George and Poulos, Serafim
Please note that others may also have edited the contents of this article.

Citation: Ghionis, George; Poulos, Serafim; (2011): Greek case studies: Morphological evolution of the R.Alfios deltaic shoreline. Available from http://www.coastalwiki.org/wiki/Greek_case_studies:_Morphological_evolution_of_the_R.Alfios_deltaic_shoreline [accessed on 28-03-2024]