This work deals with the comparative account and evaluation of the impact to the environment and especially with the alterations to the geomorphological structure and the hydro-geomorphological processes caused by the works for the diversion of the beds and the flow of rivers and torrents in the greater area of the "Katafourko lagoon" in Greece and of the "Venice lagoon" in Italy. Human intervention in the study areas, was of different aims in each location, but it all resulted in the alteration of the dynamic evolution of the hydro-geomorphological processes which has led to the creation of an "artificial" environment, controlled to a great extend by human power and which in turn, in the long term re-strengthens and reenforces the possibility of environmental destabilization

Goudelis, G.

Marabini, Francesco

Mertzanis, A.

Pantera, A.

Papadopoulos, A.

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CHINA-ITALY BILATERAL SYMPOSIUM ON THE COASTAL ZONE AND CONTINENTAL SHELF EVOLUTION TREND 
October 5-8, 2010 - Bologna (Italy) 233
WORKS FOR THE DIVERSION OF BED OF RIVERS AND 
TORRENTS AND THEIR IMPACT TO THE ENVIRONMENT OF 
THE LAGOONS OF GREECE AND ITALY 
 
Α. Mertzanis1, F. Marabini2, A. Pantera1, G. Goudelis1 and A. Papadopoulos1 
 
1
 Technological Educational Institute of Lamia, Department of Forestry and 
Management of Natural Environment, 36100, Karpenisi, Greece, amertzanis@teilam.gr  
2
 National Research Council, ISMAR, 101 P. Gobetti str., 40129, Bologna (BO), Italy, 
franco.marabini@bo.ismar.cnr.it 
 
 
Abstract 
This work deals with the comparative account and evaluation of the impact to the 
environment and especially with the alterations to the geomorphological structure 
and the hydro-geomorphological processes caused by the works for the diversion 
of the beds and the flow of rivers and torrents in the greater area of the “Katafourko 
lagoon” in Greece and of the “Venice lagoon” in Italy. Human intervention in the 
study areas, was of different aims in each location, but it all resulted in the 
alteration of the dynamic evolution of the hydro-geomorphological processes 
which has led to the creation of an “artificial” environment, controlled to a great 
extend by human power and which in turn, in the long term re-strengthens and re-
enforces the possibility of environmental destabilization. 
 
1. INTRODUCTION   
The projects for the diversion of the beds and the flow of rivers and 
torrents constitute a significant intervention to the natural and human - made 
environment of an area, especially when these projects are in a position to 
destabilize the environmental balance of the area and to alter the natural evolution 
of the parameters that are directly correlated with the creation, preservation and 
development of vulnerable ecosystems such as those of the “Katafourko lagoon” 
and the “Venice lagoon”. It is noted that for the preservation and the development 
of the lagoon ecosystems, an important parameter is the rate of supply of water and 
sediments of the lagoon site and the coastal area, as well as their qualitative 
characteristics. 
CHINA-ITALY BILATERAL SYMPOSIUM ON THE COASTAL ZONE AND CONTINENTAL SHELF EVOLUTION TREND 
October 5-8, 2010 - Bologna (Italy) 234 
 
2. MATERIALS AND METHODS   
2.1 Geographical location of the study areas 
This study focuses in to two lagoons, which have been subjected to major 
alterations of their form and their environmental characteristics due to human 
intervention. The first study area is located in Greece and the second in Italy 
(Figure 1). More specifically these areas are: a. 1stArea - “Katafourko lagoon” 
Western Greece and specifically at the eastern coast of the Amvrakikos gulf, b. 2nd 
Area - “Venice lagoon” in Northeastern Italy. 
 
 
Fig. 1 - Geographical location of the study areas. “Katafourko lagoon” Western Greece (I) 
and “Venice lagoon” Northeastern Italy (II). 
 
2.2 Geomorphology – Water resources of the study areas   
The lagoons under study constitute dynamic geomorphological systems 
where the hydro-geomorphological processes evolve at a relatively high speed. a. 
The Katafourko lagoon, in 1945, was of longitudinal, arch shape and with a size of 
approximately 2.500.000 sq. meters. It is a shallow lagoon with a mean depth of 
0.2 meters and a maximum depth of 0.6 meters and it is separated from the sea by a 
sand strip of about 1.000 meters long and a mean width of about 25 meters. 
CHINA-ITALY BILATERAL SYMPOSIUM ON THE COASTAL ZONE AND CONTINENTAL SHELF EVOLUTION TREND 
October 5-8, 2010 - Bologna (Italy) 235
Geologically speaking the bottom and the surrounding area of the lagoon have been 
formed by the deposition of earth - alluvial depositions. (Anastasakis and 
Mertzanis 1987). The “Krikeliotis” torrent which constitutes the main supplier of 
“fresh” water and sediments of the low plain area of the Katafurko lagoon, during 
the past discharged into the eastern Amvrakikos gulf while ever since 1959 due to 
human intervention it has been diverted and discharges inside the Katafurko 
lagoon. (Figure 2). b. The lagoon of Venice has a longitudinal arch shape and 
occupies an area of 550 km2, out of which approximately 11% constitutes the main 
water body, while 80% consists of swamp-marsh areas. Its length is 50 km and its 
width is 8-14 km. Nowadays the lagoon communicates with the Adriatic Sea is 
through three natural openings - channels of communication. The bottom and the 
surrounding area of the lagoon have been formed by alluvial formations-sediments 
and especially by successions of sand, sand sludge and sludge which vary in 
composition, depending on their location (Enzi and Marabini, 1992). The river 
bodies “Adige”, “Bacchiglione”, “Brenta”, “Sile” και “Piave”, which during the 
past have been discharged inside the  lagoon of Venice have already been diverted 
by human intervention and are now discharged into the Adriatic Sea (Figure 3). 
The underground water table in the greater area of the lagoon is differentiated: α. at 
the shallow well table, and β. at the deep water table under pressure (Carbognin et. 
al., 1984).  
 
3. RESULTS - DISCUSSION   
3.1 Works for the diversion of the beds of rivers and torrents and evolution 
trends of the lagoons and the coastal area – Environmental Impact 
This study focuses into two lagoons (one in Greece and one in Italy), which 
have suffered intense alterations, that is, deformations and adverse changes in their 
environmental characteristics, due to human intervention which altered the 
dynamic of the evolution of the hydro-geomorphological processes as well as their 
qualitative characteristics (Figures 2 & 3).  
These human intervention has mainly to do with: a. projects for the 
diversion of the beds of rivers and torrents which during the past were supplying 
the lagoons or the greater area of them with water and sediments, b. portal works 
inside the lagoons or at the coastal zone (ports, fishing stations etc.) as well as 
CHINA-ITALY BILATERAL SYMPOSIUM ON THE COASTAL ZONE AND CONTINENTAL SHELF EVOLUTION TREND 
October 5-8, 2010 - Bologna (Italy) 236 
industrial and touristic installations and c. exploitation-pumping of underground 
waters. 
 
  
 
Fig. 2 & 3 - Katafourko lagoon: The evolution of the Katafourko lagoon and its coastal area 
(Eastern Amvrakikos gulf), between 1945 until 1985. The new bed of the diverted 
Krikeliotis torrent and the new position of its outfall in the lagoon instead of its old 
discharge position  (before August 1959) in the eastern Amvrakikos gulf (source: 
Anastasakis and Mertzanis 1987) (Fig. 2). Venice lagoon: Schematic map of the 
diversion of the rivers into the sea and the digging of canals for inland navigation, 
(Pavanello 1931) (Fig. 3). 
 
CHINA-ITALY BILATERAL SYMPOSIUM ON THE COASTAL ZONE AND CONTINENTAL SHELF EVOLUTION TREND 
October 5-8, 2010 - Bologna (Italy) 237
3.1.1. 1st Area – “Katafourko lagoon” 
 The extremely vulnerable and “protected” ecosystem of the lagoon of 
Katafourko, ever since August 1959 and until nowadays is flooded by the water of 
the Krikeliotis torrent and at the same time is filled from the dragged materials 
from this torrent. The generation of new “artificial” hydro-geomorphological 
processes due to the artificial diversion of the bed of the Krikeliotis torrent, has 
altered the geomorphological structure and the hydro-geomorphological processes 
of the study area, and this has resulted in the shrinkage of the area of the lagoon 
and especially of its “water pane” which has assumed an area of less than 500.000 
sq. meters as opposed to the 2.500.000 sq. meters that it occupied in the year 1945 
(Anastasakis and Mertzanis 1987, Mertzanis 1992). At the same time in the coastal 
zone, have been generated conditions of erosion and regression of the coast line, 
due to the drawing away of the outfall of the Krikeliotis torrent from the eastern 
Amvrakikos gulf and as a consequence the deprivation of the coast from dragged 
material (Figure 2). The phenomena of erosion and regression of the coast line, at 
least in the northern part of the sand strip which separates and “protects” the lagoon 
of Katafourko from sea action, appear to be enforced due to the inhibition of the 
natural movement of sediments in the coastal - sea area due to the construction of 
the port -fishing station in the last 15 years.  
 
3.1.2 2nd Area – “Venice lagoon” 
The “Venice lagoon” nowadays is more and more submerged by sea 
flooding "acque alte", as a result of the combination of the natural processes and 
especially of the climatic changes and the human intervention (river diversion, 
deepening of navigation channels, over pumping of underground waters in 
industrial locations etc.). More specifically the natural evolution of the “Venice 
lagoon” has been altered as a result of human intervention, where for defense 
purposes but also for commercial reasons were constructed already ever since old 
times, (1300-1800 a.C) projects for the diversion of the Adige, Bacchiglione, 
Brenta, Sile, Piave and Po aiming at their discharge outside the lagoon so that its 
filling with dragged material could be avoided (Teodoro Viero 1799) (Figure 3). 
Similar interventions were seen until the XIX century which hindered the filling of 
CHINA-ITALY BILATERAL SYMPOSIUM ON THE COASTAL ZONE AND CONTINENTAL SHELF EVOLUTION TREND 
October 5-8, 2010 - Bologna (Italy) 238 
the lagoon with sediments and the union of the island-town of Venice with the 
mainland and created such a situation that would allow the predominance of the sea 
processes as opposed to the river-terrestrial ones, and this resulted in the 
intensification of the erosion phenomena of the coastal area and especially of the 
thin sand strip which edges in and separates the lagoon from the Adriatic sea and 
which constitutes an important geomorphological characteristic for its protection. 
There were also interventions for the purpose of the enforcement and the protection 
of the sand strip which separates the lagoon from the Adriatic Sea and this resulted 
to the creation of an artificial lagoon environment which is as far as possible 
controlled by man. The above interventions were followed by intense over 
pumping of underground waters which resulted in the subsidence "subsidenza" and 
the lowering of the soil surface of the lagoon area and the sand strip (Pavanello 
1931, Gatto & Carbognin 1981, Carbognin et al. 1985, Carbognin and Marabini 
1989, Marabini and Veggiani 1991). 
 
4. CONCLUSIONS 
In the study areas the projects for the diversion of the rivers and torrents 
constitute human intervention of totally different aims which were: a. In the case of 
the Katafourko lagoon, banking up, and the consequent shrinkage of the lagoon 
area, by the dragged material from the Krikeliotis torrent. For this purpose, the 
artificial diversion of the bed of the Krikelioti torrent was constructed, which 
resulted in its discharge (outfall of the torrent) in the Katafourko lagoon instead of 
into the Amvrakikos gulf and b. The avoidance of the filling of the Venice lagoon 
with the dragged material brought by the rivers which discharge into it, for 
defensive but also for commercial reasons. Works for the diversion of the rivers 
Adige, Bacchiglione, Brenta, Sile, Piave and Po have been constructed so that the 
rivers will discharge outside the lagoon. Also there were digging works for the 
deepening of the navigation channels. 
 
REFERENCES 
Anastasakis G. , Mertzanis A. (1987). – The evolution of the outfalls of the 
Krikeliotis torrent (Eastern Amvrakikos) and the effect of the artificial diversion on 
CHINA-ITALY BILATERAL SYMPOSIUM ON THE COASTAL ZONE AND CONTINENTAL SHELF EVOLUTION TREND 
October 5-8, 2010 - Bologna (Italy) 239
the dynamic of the coastal area. Minutes 2nd Hellenic Conference of Oceanography 
and Fishery, 1987, Athens, pg. 464-470. (in Greek) 
Carbognin L., Gatto P., Marabini F. (1984). The city and the lagoon of Venice – a 
guidebook on the environment and land subsidence. In: Proc of the III Congresso 
Internazionale sulla subsidenza, Venezia,  pp. 1-35.  
Carbognin, L., Gatto, P., Marabini, F., (1985). Εrosive processes in the littoral of 
the Venice lagoon, Coastal zone 85, IV Symposium on coastal and ocean 
management, Baltimore, U.S.A., 1587-1600.  
Carbognin L., Marabini F., (1989). Evolutional trend of the Po river delta (Adriatic 
sea, Italy), Proc. of the 28th International Geological Congress,  Washington D.C., 
U.S.A., pp. 238-239. 
Enzi S., Marabini F., (1992). Evoluzione della fascia costiera Adriatica e l’azione 
antropica, Proc. of the Congress Asociazione Italiana di Cartografia, Bolzano, 
Italy.  
Gatto, P., Carbognin, L., 1981. The lagoon of Venice: Natural environmental trend 
and man-induced modification, Hydr. Sc. Bull. 26.  
Marabini F., & Veggiani A. (1991). “Evolutional trend of the coastal zone and 
influence of the climatic fluctuations. The Second International Symposium on 
Coastal Ocean Space Utilization. Long Beach, CA (U.S.A). 
Mertzanis Α. (1992). “Geomorphological Evolution of the Gulf of Amvrakikos”. 
PhD Thesis, Geology Department of Athens University.Athens, Greece. (in Greek). 
Pavanello, G., 1931. La Laguna Veneta. Note illustrative e breve sommario storico, 
Venezia, Magistrato alle acque, Ufficio speciale idrografico, 1-34.  
Viero, T., (1799). Ricostruzione della laguna di Venezia nell’ anno Domini 1000, 
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Works for the diversion of bed of rivers and torrents and their impact to the environmental of the Lagoons of Greece and Italy

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Works for the diversion of bed of rivers and torrents and their impact to the environmental of the Lagoons of Greece and Italy

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