The streams and water courses of Thessaloniki have historically served as crucial reference points for various important activities, even before the city’s founding. As detailed by G. Blionis and M. Tremopoulos in their systematic review of the city’s streams and water resources, both from a historical and ecological perspective, entitled “Thessaloniki of Waters” (Antigone Publications), proximity to water sources and streams was a key factor for the self-sufficiency and longevity of settlements from the Bronze Age to the present day.
However, over the course of history, particularly during periods of intense urbanization, practices such as landfilling, straightening, boundary restriction, and encasing streams in wire cages destroyed the beds of many water courses and a significant portion of the riparian vegetation, prioritizing construction over preservation.
These methods resulted in the ancient streambeds within the city walls becoming forgotten. Nevertheless, water’s “memory” of its original routes resurfaces during heavy rainfall, leading to increased speed of flood waters, increased risk of debris being dragged along and even loss of human lives. Simultaneously, the complete sealing of the soil through infrastructure development and the use of impermeable materials significantly reduced water infiltration and absorption by the ground1.
In recent years, efforts to address the growing frequency of extreme weather events caused by the climate crisis, the pronounced urban heat island effect, and the need for public and free spaces have shifted the perception that streams, water channels, and wetlands are problems to be eliminated by making them disappear.
While at the European level, the protection of wetlands and waterways has become a priority, in Greece, until a few years ago, their protection was regarded as a quirky obsession of ecological and environmental organizations. It took severe flood events and threats to human lives for the gravity of the situation to be recognized, leading to slow changes in practices.
It is a fact that most of the water courses that existed in Thessaloniki before the construction of the peripheral water channel in the eastern part of the city no longer remain. Only small sections of their open beds have been preserved.
To delve deeper into this issue, we visited significant wetlands and waterways with Giorgos Blionis PhD2, a biologist-ecologist, and Petros Kakouros3, a forester-environmentalist, in an effort to identify the main problems facing our city.
Stagiritis Water Course
“The two largest and most significant streams in the Thessaloniki area are Dendropotamos in the west and Anthemountas in the east. Essentially, we are talking about rivers, or at least that’s how they were historically described. Anthemountas is mentioned as far back as the era of Alexander the Great because the region of Vasilika hosted a thriving community that provided horsemen for Alexander’s elite cavalry, the famed Anthemousian Squadron. This underscores the importance of the Anthemountas area since ancient times. Within this broader area, there are about six to seven smaller streams now located within the city’s urban fabric. The largest of these is the Megalo Rema (Great Stream), of which the catchment area includes the Stagiritis-Malakopi water course, the Elaionrema (Olive Stream), the stream descending from Panorama, and several smaller ones, explains G. Blionis.
Blionis elaborates, “The water used to flow through the Charilaou and Toumba neighborhoods, past the Kalos Garden, and ended up in one of two directions; either towards the present-day Folklore Museum or towards what is now the 5th Gymnasium School, nearThessaloniki Concert Hall. Now the peripheral water channel collects the flood runoff. Between these two lowland sections of the runoff basin was the Exoches district, now better known as the Analipsi neighborhood. It’s no coincidence that in the late 19th century, when the city expanded beyond its walls, all the wealthy villas of Thessaloniki were built there. The microclimate is cool in the area, trees were planted, it has access to the sea and connects the natural environment with the city’s history and architectural heritage”, Blionis adds.
Regarding the Stagiritis-Malakopi stream, Blionis clarifies that it originates from the Seich Sou and flows into the peripheral water channel (at the junction of Stagiritis and Dimos Tseliou streets) in the municipality of Pylaia-Chortiatis. During the construction of the ring road in the 1980s, part of the streambed was filled in, causing the natural water course to change abruptly and continue to flow underground via pipes. The stream has also suffered from other controversial interventions, including straightening and the installation of wire cages, which narrowed its bed and destroyed its vegetation. At the Seich Sou elevation, only one of its three mountain tributaries maintains an open, natural bed, albeit with minor interventions (wire cages) up to the Roman aqueduct in Pylaia.
The recent Fly Over construction works further complicate the stream’s future. As G. Blionis points out, the impact of these projects, which involve design-and-build contracts, is unclear since their ramifications are not pre-assessed. Concerns arise over the extensive interventions in sections of the water course that have not yet been officially delineated and the potential problems that may be created.
What If the Daniel Weather Event Had Moved Further North?
This question was posed a year and a half ago by the municipal group “City Upside Down” and Michalis Tremopoulos, leader of the municipal group “Ecology-Solidarity”, in the wake of Storm Daniel in September 2023. The storm, which devastated the broader region of Thessaly, caused immense destruction and led to the loss of both human lives and livestock.
“Ethnikis Amynis Street would revert to its old form as the Evangelistria river. The ground floors and basements of stores along its entire length, from the Sintrivani Fountain to the White Tower, would be at risk of flooding. Nearby, the Chortatzides water course, which runs through the Thessaloniki International Fair (TIF) area, would wreak havoc on its facilities,” noted the local municipal group City Upside Down at the time in reference to one of the many parts of the city once traversed by natural water courses which are now buried, enclosed in pipes, or channeled underground. This includes the TIF water channel, where streets turn into rivers during heavy rain.
A striking example of the potential consequences of these buried torrents occurred in May 2018 at the South Gate of the TIF grounds, in the area which traditionally hosts the annual Flower Exhibition. A heavy downpour swept away all the flowerpots and beds, starkly reminding the city of the repercussions of encasing waterways in concrete within urban areas.
This recurring issue highlights the reasoning behind the calls for relocating the TIF grounds and transforming the area into a metropolitan green park. Far from being a reckless act, this idea is seen by city movements and collectives as a calculated, realistic approach aimed at serving the genuine interests and improving the quality of life of Thessaloniki’s residents.
The Peripheral Water Channel
A pressing question for many is how the Peripheral Water Channel responds to heavy rainfall, whether it can handle such a large volume of water and whether the underground streams of Yfanet in Toumba, and the Governor’s Mansion will withstand the pressure or pose risks to adjacent roads.
“In 1955, as we document in our book Thessaloniki of Waters, the peripheral water channel was constructed in the eastern part of the city specifically to address severe and increasingly frequent flooding in areas such as Analipsi, Faliro, and even around the White Tower. This major engineering project redirected floodwaters from most waterways descending from the Seich Sou forest. However, it left the stream beds downstream exposed to even greater pressure because they were deemed inactive and were repurposed for various uses”, explains G. Blionis. He notes that “above the peripheral water channel, several streams remain open. Thankfully, since the 1990s and with the growing discourse on the value of waterways, a new approach has emerged: keeping the beds open with interventions like straightening and stabilizing the beds using wire cages ”.
However, Blionis acknowledges that while this method offers advantages compared to earlier practices of burying and enclosing water channels, it still falls short of natural standards. Trees, he emphasizes, “are more effective along riverbanks and offer a far more natural method of stabilizing the bed. Instead of wire cages, we could adopt a mixed approach using boulders and trees. We know, from visits to natural plane tree forests and riverbanks, how plane trees with their trunks and roots play a significant role in stabilizing stream banks”.
Scientists considering the impacts of climate change advocate for additional natural solutions for waterways, such as retention basins. “This means creating a natural lake adjacent to a torrent bed that can act as a buffer during heavy rainfalls. However, this requires preserving open spaces in urban environments. These areas should not be used for construction or public infrastructure, so we can better manage extreme weather events in the future. These solutions not only address environmental challenges but also offer residents opportunities for improved quality of life”, he concludes.
Dendropotamos: A Heavily Disturbed Ecosystem That Still Survives
In the western part of Thessaloniki, the flood basin of Dendropotamos has been recorded for centuries, as documented in the book by Blionis and Tremopoulos. Historically, these floods caused no damage since the stream’s bed was in a largely uninhabited area. However, its impact began to grow with urban development in the 1960s, culminating in the catastrophic 1972 flood, which prompted a study for the channeling and regulation of the stream’s lower, populated section. By the 1990s, the bed of the man-made water channel in Evosmos was covered, and Dendropotamos Avenue was constructed. Most of the Dendropotamos stream and its tributaries, especially in the Efkarpia area, are now covered. Despite the remaining vegetation, the area has been severely degraded due to industrial activity, quarries, the TITAN cement factory, and more recently, the Efkarpia Waste Transfer Station (WTS). Only a small section of the Dendropotamos water channel near its origin remains open. As Blionis and Tremopoulos note, this area is home to oil storage tanks, tanneries, and cement-loading facilities, which contribute to occasional foul odors.
According to Petros Kakouros, despite its ongoing pressures, the Dendropotamos area remains significant as the eastern boundary of the vast wetland system encompassing the Axios, Gallikos, Loudias, and Aliakmonas rivers
“The river, despite its diversion, managed to form a new deltaic system, which, though heavily disturbed, still connects to the Kalohori area in the west. This area continues to face serious pressure from infrastructure development, heavy industry, and traditional uses such as slaughterhouses which are not currently operating. However, it retains considerable natural value and, with proper ecological restoration, could become a green oasis”.
The second aspect that underscores the importance of the Dendropotamos area is its role in protecting the land from extreme weather events originating from the sea. P Kakouros explains, “The climate crisis, as we’re already experiencing, increases wind speeds and the intensity of weather events. This means we need a coastal defense system to prevent seawater intrusion into inland areas. These inland infrastructures, especially in agricultural zones, are highly vulnerable to saltwater. Wetlands are excellent for carbon storage due to their water presence. Their year-round high biological activity, especially in warmer temperatures, makes them critical ecosystems”.
Until the late 1970s, such areas were globally considered “useless,” leading to efforts to drain and fill them. This perception, Mr. Kakouros explains, has since changed.
“With scientific contributions, it was proven that wetlands are far from useless, they provide significant ecosystem services, some with substantial economic benefits. In Thessaloniki, for instance, mussel farming in the Delta area is a highly profitable activity employing many people. Even at the Dendropotamos estuary, there is an informal anchorage for fishing boats, indicating that the area is far from lifeless, it has fish and life” he concludes.
Unified Coastal Front: A Plan Still Stuck in Studies
The coastal zone of Thessaloniki, stretching from Kalohori to Peraia, has long been the subject of studies aiming to unify it into an environmentally sound, accessible area. Despite various studies by relevant authorities for its protection, true political will seems absent. Over 15 years have passed since these plans were first discussed, and progress remains confined to the study phase.
“The Unified Coastal Front project seems to overlook two critical factors”, explains Yiannis Krestenitis, Emeritus Professor of Coastal Engineering and Oceanography, to Alterthess. “First, it faces the sea, which needs to be clean. Second, it disregards the climate crisis, which exacerbates coastal erosion, rising sea levels, and phenomena like coastal flooding, which we have already experienced.” Krestenitis notes that coastal erosion is not unique to Thessaloniki and is expected to worsen under climate crisis predictions.
Krestenitis stresses that addressing this phenomenon should not involve grandiose engineering projects to push back the sea. Instead, solutions closer to nature are needed, such as expanding the coastal area. Unfortunately, this approach does not seem to align with current policy choices. He points to a recent amendment to shoreline legislation as evidence, “Once again, we failed to incorporate the provisions of the Barcelona Protocol into our laws. The protocol stipulates that human activities, urban, tourism-related, agricultural, etc. should begin at least 100 meters inland from the shoreline. Here, unfortunately, the coastal zone remains narrow, often reduced further to serve various proposals and interests”.
In any case, it is evident from the statements made by the Deputy Regional Governor of Thessaloniki, Kostas Gioutikas, to Alterthess, that the unification of the coastal front spanning 40 kilometers from Kalochori to Aggelochori has not yet begun, as it remains stalled due to the pending issuance of a Presidential Decree. “The Presidential Decree is still pending due to the ministry. We have submitted all the studies and made all the requested corrections. The ministry needs to finally progress so that we can establish a foundation”, he stated when asked about the issue.
“The foundation involves specific, unified land uses so that the entire coastal front can be planned comprehensively and all necessary resources can be secured, whether they come from state funds, European funds, NSRF resources, or even private investments, to complete such a large and emblematic project”, he added. Furthermore, he mentioned that the Region of Central Macedonia has, in the meantime, begun the cleanup and restoration of six kilometers along the Gallikos River. Plans are also underway to extend the “Red Trail” for the creation of a cycling path and to establish a maritime stop at the boundaries of the Delta Municipality and the Menemeni-Ampelokipoi Municipality.
What Thessaloniki truly needs is a comprehensive spatial planning framework according to scientists, organizations, and activist movements; that is a regulatory plan with binding provisions to ensure even a basic level of progress toward protecting its natural environment, biodiversity, and, of course, human life. As Petros Kakouros puts it: “At the moment, we have a mishmash of specialized spatial plans and specific studies, one for the former Pavlos Melas military camp, another for the Thessaloniki International Fair (TIF), yet another for the coastal front, Dendropotamos, and Kalochori. None of these are interconnected. And how can all these plans claim to promote resilience when a critical aspect of transitioning to a resilient city is having a cohesive plan? No one can explain why this is happening”.
Research and editing: Jason Bantios, Stavroula Poulimeni, Tilemachos Fassoulas
Up next: ThessINTEC: The End of a Wetland in the Name of “Innovation”
The research of the independent media cooperative Alterthess titled “Urbal Resilience, Climate Neutrality: The case of Thessaloniki” was realised with the support of Rosa Luxemburg Stiftung-Office in Greece. Read the complete research here.
- Stavros Tsoumalakis, Master’s Thesis: The Streams of Thessaloniki, Spatial and Hydraulic Perspective, October 2017 [↩]
- The interviews with Giorgos Blionis took place in April and May 2024 [↩]
- The interview with Petros Kakouros took place in July 2024 [↩]
