Filenews 12 June 2025 - by Vasos Vassiliou
There are about 2,000 landslides in Cyprus of which 500 are active. The number is terrifying, but the only option that seems to exist is to learn to live with them and avoid constructions where the Geological Survey Department indicates that the soil is not suitable for developments.
According to the Geological Survey Department, in the wider area of Pissouri and Petra tou Romio there are several landslides mapped, with the most important ones being on the highway near the community while a third area is located on the coastal road of Petra tou Romiou.
The situation in Pissouri, as it has been shaped in the last 80 years or so, is as follows:
The traditional core of the community is built on an old landslide of 75,000m2. The first recorded large landslide hit Pissouri in 1937 resulting in a large mass of land landslide and again, after the great earthquake of 10/09/1953, resulting in a death. In 1957, after a study and recommendation by the Geological Survey Department, 7 families were moved. In 2001, a small failure had occurred approximately in the center of the old landslide, causing serious damage to 3 buildings.
In order to deal with the instability, retaining works (a wall and a counterweight) were constructed, which were completed in 2011. In November 2019, after a failure of a monitoring well near the wall, the Department proceeded to survey cracks in the village and drill monitoring wells.
The area of Limnes consists of a paleo-landslide with an area of 453,000m2 which began to be built in the 90s and currently contains around 250 residential units in the mass of the landslide (and 125 in the crown). The toponym "Lakes" probably refers to the stagnant waters that were retained in the anomalous topographic relief in the mass of the landslide. In 2012, the first surface cracks appeared, an indication of the activation of the landslide.
The Geological Survey recommended the construction of a suitable rainwater drainage system and undertook the installation of inclinometric pipes in boreholes to monitor the movement. In 2019, the Ministry of the Interior commissioned a private company to study the landslide of the Lakes, resulting in the construction of 2 pile walls, a counterweight and various projects for rainwater drainage and the lowering of the aquifer. So far, the construction of the first pile wall has been completed.
In the summer of 2023, the Geological Survey Department informed about the discovery of gypsum rocks and underground gaps in a deep borehole in the area of Limnes, resulting in a decision of the Council of Ministers giving time credit for further investigation. By decision of the Council of Ministers, the TEGI, following the instructions of the Steering Committee, has drawn up and has already implemented an Action Plan for further investigation and treatment of the effects of the two landslides.
The Action Plan consists of four pillars:
A. Geological Model – aims to better understand the geological model and the geomechanical parameters that cause the landslide phenomenon
B. Monitoring – aims to monitor the movement of landslides, at the depth of the slide surface but also at the surface of the earth
C. Stabilisation Measures – aims to carry out projects aimed at stabilising travel as much as possible
D. Civil Protection – aims to protect the citizen
Each pillar is summarised below, where the actions that have been completed and the actions that are proposed or have already been rolled out are mentioned. The actions are carried out by the Geological Survey Department, the Water Development Department, the Limassol District, the Civil Defence, CUT, the community and private designers, all with a state budget.
A. GEOLOGICAL MODEL
Completed:
1. Detailed geological and tectonic mapping with deep drilling and paleontological determinations
2. Construction of geological trenches
3. Photogrammetry for the acquisition of topographic relief and high-resolution aerial photography
4. Hydrogeological model with deep boreholes, drainage tests and chemical analyses for drainage system design
5. Geophysical and geological surveys to confirm tectonic structures and slip surfaces
6. Construction of a 3D digital geological model Programmable:
1. Continuation of the collection of geological and geomorphological data that will also contribute to the identification of new areas suitable for residential development
2. Further geotechnical laboratory tests on the marlar rocks of the area
3. On-site Geotechnical Tests with Portable CPT – (CUT)
4. Reverse analysis of safety indicators of the two landslides
B. MONITORING
Completed:
1. Acquisition of satellite stringometry data (InSAR) for surface movements from 2021 to 2023
2. Installation of conventional crack meters to monitor cracked homes
3. Drilling of boreholes, installation of inclinometers and monthly movement monitoring
4. Mapping of ground cracks.
5. Installation of 6 GNSS stations in buildings and interconnection with the CYCLOPS network (a total of 10 stations in Pissouri)
6. Operation of a web portal for 24-hour monitoring of the 10 GNSS stations.
7. Geotechnical Data Collection.
Planned:
1. Drilling of additional boreholes for the installation of additional inclinometers.
2. Installation of electric inclinometers at least one point for each landslide in order to monitor and strengthen the early warning system 24 hours a day
3. Acquisition of new satellite stringometry data (InSAR) for surface movements from 2023 to 2025.
4. Installing more conventional crack gauges to monitor cracked homes
5. Installation of 20-30 electronic automatic monitoring crack meters that will allow the immediate (from the office) and 24-hour monitoring of cracks in masonry, roads, etc., with the ultimate aim of strengthening the 24-hour monitoring web portal
6. Continuous mapping of ground cracks
7. Installation of an accelerometer to record ground acceleration
C. STABILIZATION MEASURES
Completed:
1. Re-evaluation of the retaining wall on Anexartisias Street (P. Papadopoulos)
2. Evacuation of septic pits of all premises in the area of the two landslides and around them on a continuous basis Design and construction of 24 drainage wells of large diameter and depth along with neighbouring pieziometric wells (21 boreholes in Limnes and 3 in the core of the village based on the hydrogeological model)
3. Installation of pumps and drainage from the 3 boreholes of the village core
Planned:
1. Drilling of drainage holes in the retaining wall on Anexartisias Street (to be completed in June 2025)
2. Evaluation of the static adequacy of the retaining wall in the Lakes (Purchase of Services)
3. Restoration of the topographic relief along the retaining wall in the Lakes to fill the gaps created by its displacement, for the purpose of public safety (Purchase of Services
4. Operation of the existing central sewerage system in the square in the center of the village
5. Study for the construction of a sewerage system in the rest of the community of Pissouri.
6. Management of large losses in the water supply network
7. Immediate start of drainage in the Lakes.
8. Preparation of a hydrological study in the wider built area for the management of rainwater
D. CIVIL PROTECTION
Completed:
1. Inspecting the houses for their suitability
2. Application of Geological Suitability Zone 00 – White Zone
3. Informing the citizen through the geoportal of the T.G.E.
4. Completion of the Evacuation Plan
5. Installation and operation of Siren
Planned:
1. Continue the inspection of the houses for their suitability
2. Implementation of Geological Suitability Zone 01A around the existing White Zone. Special conditions – restrictions will apply in this Zone that will be an integral part of Urban Planning Permits
3. Operation of an early warning system, which will be powered by the data of the GNSS stations
4. Operation of an early warning system, which will be powered by the data of electronic crack meters and electronic inclinometers
5. Informing residents about the evacuation plan, issuing information leaflets and scheduling exercises
6. Construction of dirt roads and other works to facilitate a possible evacuation
7. It is emphasized that the commencement of drainage of the area of the Lakes as well as the preparation of a study and construction of a sewerage system in the stable areas of the community are of major importance. At the same time, the preparation of a hydrological study for the management of rainwater in the entire residential area, and the study for the identification of losses from the water supply network, are equally important. The best possible management of surface and groundwater in landslide areas is the most important and effective measure to slow down/mitigate the effects of the phenomenon.
The uses that exist in the designated White Zone will remain unchanged and any construction work will be terminated. (Virtually the white zones are made permanent)
