Stream demarcation: when it is needed

Streams are demarcated under the procedure of Law 4258/2014. Demarcation (οριοθέτηση ρέματος) is required before technical works near a stream and is often a precondition for a building permit on a property next to a stream. It is also needed in urban planning studies, in stream training works and for roads that cross streams.

Next to a stream that has not been demarcated, building is allowed only by way of exception: on the application of the interested party, the Building Service carries out a provisional demarcation. This needs a hydraulic study for the whole catchment up to the demarcation point and flood lines for a 50-year return period on a topographic survey plan, checked by the Technical Service of the Region. Building is allowed outside the flood lines and at the distances set by law.

What the demarcation file contains

A topographic survey plan in plan and elevation, at a suitable scale, tied to GGRS87 (ΕΓΣΑ87), the national coordinate system of Greece, with cadastral data where needed
A hydrological and hydraulic study, with the flood discharge and the flood lines
A technical report on the geological and geomorphological conditions, and an environmental report
A demarcation proposal with the boundary lines of the stream

The file can also be prepared by a private individual or company, with studies signed by qualified engineers. After opinions from the competent services and the municipality, the demarcation is ratified by the Decentralised Administration or the competent ministry, depending on who examined the file, and the act is published together with the survey plan.

The ground under the trees

A hydraulic study is only as good as the relief of the stream bed and banks. Streams almost always have dense vegetation, where photogrammetry sees only the tops of the trees. There we use drone LiDAR, which reaches the ground between the leaves, and complete it with GNSS and total station measurements in the bed. Where there is water, the bed is also measured by bathymetric survey. In the Agrafa mountains we produced the terrain model for the hydraulic study of a stream demarcation in this way, inside a mountain village. See the Agrafa stream project.

Foreshore and beach zone

The foreshore (αιγιαλός) is the strip of land reached by the largest usual run-up of the waves, and the beach zone (παραλία) is the strip of land added to it. Both are public, and their delineation affects building, property transfers and any use near the sea. The law in force today is Law 5092/2024.

The lines are set by a Committee at regional-unit level, chaired by the head of the State Property Service (Κτηματική Υπηρεσία), after a site inspection and on criteria such as the shape of the coast, the vegetation and wave data. For the old foreshore, traces on the ground, aerial photographs and old maps are taken into account. The decision is recorded on the Cadastre's orthophotos and published in the Government Gazette (ΦΕΚ). If there is an error or a change, a re-delineation takes place: private owners can request it from the State Property Service with a technical report, a survey plan of the zone and, where it concerns their own property, their title deeds.

What we provide

Our role is the survey base: the topographic survey plan in plan and elevation in GGRS87, the terrain model, the cross sections of the bed and, on the coast, the survey of the zone. The hydraulic study, the reports and the demarcation proposal are prepared by the competent designers, with whom we work on the cross sections and the model they need.

What you need / steps

The location of the property or study area, the title deeds and, if available, the KAEK (the 12-digit cadastral code)
A check on whether the stream or the foreshore has already been demarcated, and by which act
A topographic survey of the zone, with LiDAR where there is vegetation and bathymetry where there is water
For a stream: working with the hydraulic engineer on the cross sections and the terrain model
Delivery of the survey plan and the files for the demarcation file

If your property or study borders a stream or the sea, send us its location so that we can see what has already been demarcated and which survey data the file needs.

Stream and foreshore demarcation: when you need it and what it involves