On September 25, 2023, the competent Directorate of Environmental Licensing of the Ministry of Environment and Energy (DIPA/YPEN) gave the green light to carry out flood control work on the rivereke Kifissoswhich is the main recipient of rainwater in the basin of the Greek capital.
This allows the Ministry of Infrastructure and Transport’s Flood Management and Improvement Authority (MIPYME) to prepare tender documents and proceed with the competition for their construction.
Projects published in the Sunday edition of the newspaper “Vima” of September 17, include the settlement of two sections of the Kifissos River “Τρεις Γέφυρες – Κόκκινος Μύλος” and “Κόκκινος Μύλος-Αττική Οδό ς”, as well as the construction of a retention pond to retain flood waters, i.e. “lake” in which water will be retained for several hours in case of extreme rainfall, and then gradually released into a closed section of the river (flowing under the National Road from Three Bridges to Faliro). The goal is to reduce the risk of flooding in surrounding areas.
In the project study, retention pond size was calculated for 50-year (50-year return period), 100-year, and 1000-year rainfall. However, based on rainfall occurring once every 50 years, the volume of excavation required to create the pond in the first stage is estimated to be approximately 300,000 cubic meters, and the depth of the pond at its maximum level will be about 15 meters. The reservoir will be located parallel to the National Road, in the west, above the intersection with the Attica road, and will extend within the areas of Acharnon and Metamorfosi.
According to the approval of environmental conditions (AEPO) signed by the director of IHU, Mr. Costas Dimopoulos, the project consists of three separate parts.
Part of the “retention pond” work will involve work on a 1,650m section of the river that is in a natural state. These works will expand the existing catchment area to reduce peak flood flows during major flood events in downstream sections of the river. The catchment will only hold water for a few hours during floods with a high return period. The catchment area for peak flood flow reduction (for a 50-year return period) is estimated to be 106,000 m2.
The catchment will operate when the water flow exceeds 168 cubic meters per second (m3/s), and with a lower flow rate the system will work the same as it does today. The project will include, but is not limited to, work to regulate the flow using a vertical wall covering the inlet from one level upward. The filling time of the reservoir will be up to 2 hours 15 minutes.
Two schemes on Kifissos
In addition to the retention pond, the work will include two river developments. The 1st section “Τρεις Γέφυρες – Κόκκινος Μύλος”, 3.3 km long, will include reinforced concrete works that will widen and change the existing cross-section of the river. The new section will remain open.
The second section “Κόκκινος Μύλος-Αττική Οδός”, with a length of 2.15 km, will include works to regulate the riverbed of the Kifissos River, which is largely in a natural state, despite numerous human interventions (for example, concrete shoulders at the edge of the riverbed) and related associated work. Works have been proposed for this section, mainly using wire mesh, which will widen and alter the existing cross-section of the river for 1.94 km, while no settlement work is planned for 216.50 m.
All three flood protection works on the Kifissos River include associated works such as the construction of new road bridges, pedestrian bridges, a water bridge for the EVDAP pipeline (dismantling and reconstruction), restoration of roads, pavements, networks and vegetation.
According to ΑΕΠΟ, the work to regulate and delimit sections of the Kifissos River is compatible with the new Athens Regulatory Plan (ΡΣΑ) and the institutional framework for the protection of the river, as well as with the river basin management plan of the Attica District. The River Basin Management Plan includes 49 planned projects and project proposals within the framework of the Operational Program “Environment – Sustainable Development” (ΕΠΠΕΡΑΑ). These include storm drainage networks, stream management and other flood protection projects.
There are no environmentally sensitive areas within the project area – protected areas of the Nature 2000 network (Natura 2000), areas designated as landscapes of special natural beauty (ΤΙΦΚ), wildlife reserves and wetlands.
However, changes will need to be made to city plans. This is because in general the project is compatible with the provisions of the general urban plans (ΓΠΣ) of the area, with the exception of the urban plan of Nea Chalkidona in the area of Kifissos Bridge and the Palamas intersection, which is being developed in the area allocated for the playground and the urban plan of Acharnon, where the projects are being developed within the adjacent parts of the Hamomilu-Likotripa urban plan.
There are no declared archaeological sites in the project’s area of influence. However, there is a cultural heritage site (the post-Byzantine aqueduct) that should be protected and developed.