Quantity floods is increasing in our country. Except that this conclusion cannot be attributed solely to extreme weather conditions and climate change. In our country, with an extremely heterogeneous topography favoring flash floods, the change in vegetation cover and its use seems to play a more important role than the increase precipitation. According to experts, obsolete ones (whether technically or in terms of “power”) are also brought into play. flood control projects.

According to scientific studies published in recent years, the areas most frequently flooded are Attica, Thessaloniki, the major cities of Thessaly, Peloponnese and Crete, as well as the area around the Evros River, which is the largest “interstate” river. . “Of course, in recent years, serious floods have occurred in areas that have not experienced similar problems, such as Mandra Attika and Muzaki Karditsa,” says Vangelis Baltas, Professor of Hydrology and Water Resources Management, NTUA Faculty of Civil Engineering. “There have always been floods in our country. Greece has about 18,000 km of coastline, which means a very large number of watersheds, which are usually relatively small. These pools are fast-acting, that is, the time for the accumulation of water in such quantities as to cause a flood is short. It seems that in recent years, not only the number of floods has increased, but also their adverse effects. This fact is likely due to changes in land cover and land use due to projects and urbanization and, of course, climate change.”

Fatal interventions

The areas most often flooded are Attica, Thessaloniki, the major cities of Thessaly, Peloponnese and Crete.

In recent years, human intervention has proved fatal in many areas. From rivers and streams turned into roads, buildings “grown up” on the banks of rivers, embankments, to the transformation of floodplain river deltas into resort areas. “In my opinion, human intervention in watersheds plays an important role. We must not ignore the fact that our infrastructure often becomes outdated. For example, storm or sewer networks built 40-50 years ago are logically no longer able to respond. However, at the scientific level, the trend is to combine technical projects with so-called “natural solutions” such as reservoirs, which better “marry” the natural environment. Finally, let’s note the role played by natural disasters – such as forest loss – in further burdening the benefits of flooding.”

He agrees with this point of view. Michalis Diakakis, a researcher at the University of Athens, who has systematically dealt with flood phenomena in recent years. “In my opinion, the main problem is human interference in streams. When streams have a naturally formed floodplain, which is necessary for the water to flow freely into the sea, and in it a person has erected obstacles – roads, buildings, structures – this in itself makes it difficult to “smooth functioning”. Rivers flood more easily and more often, and for this reason we have had more disasters in recent years.” In this sense, one would expect that in areas such as Zakynthos (and the Ionian Islands in general), where rainfall is consistently higher than in the rest of Greece (and therefore not many dry rivers that are routinely trampled), floods will be less frequent. “Of course, in the Ionian Islands and in Epirus, the geo-environment and vegetation are much better prepared for more rainfall. But there is always a limit. A strong storm will cause problems. In addition, due to their special geological conditions, rockfalls and mudflows occur, which are aggravated, in particular, in Zakynthos by the consequences of forest fires of recent years,” says Mr. Diakakis.

Problems in Attica

On the contrary, problems in Attica are… permanent. “In Attica, there is very intense interference with the hydrographic network, critical sections are reduced, there is a transfer of materials and waste in the streams, as a result of which this is an area that constantly has a high frequency of floods. In some cases, like Mandra, Rentis and Marathon, the situation has improved after some maintenance work. But there is a large area in the western suburbs, from Ano Liosia to Egaleo, where the rivers still overflow, because their channels and floodplains are built up. Such interventions cannot be easily reversed.”