Demarcation Study for the construction of the project "Emergency Flood Barriers from the railway line to the mouth of the river"

Demarcation Study for the construction of the project “Emergency Flood Barriers from the railway line to the mouth of the river”

Selinountas River - Ahaia

In the north-eastern part of the Regional Unit of Ahaia, south-east of the city of Egio, the river Selinountas passes. The study area included part of the river below the railway line, as well as the “Myloi Angelopouloi” location where the existing embankments had been destroyed. The study concerned the flood protection of the riparian agricultural lands as well as the protection of the wider ecosystem of the river. In particular, the study sought to ensure a sufficient hydraulic cross-section of the studied sections, to ensure the riparian zone from encroachments, as well as to strengthen the protection of the wider riparian ecosystem. The projects aimed to contribute positively to the development of the area and to raise the standard of living, as phenomena of a strong flood nature and strong flows on the roads and properties will be avoided. In addition, demarcation was required for future inclusion of riverside areas within a city plan, for the issuance of building permits to riverside properties as well as for transfers of riverside land and other real estate.

Information

Taking into account the Survey Study and the on-site autopsies in the study areas, as well as the hydrological study that was carried out, it emerged:

Hydraulic adequacy control of the existing active and wide riverbed with a total length of about 136.00m. regarding the location “Myloi Angelopouloi” and about 300.00m. regarding the area downstream of the Railway Line, for flood benefits of long return periods (T=50 and T=100 years).
Arrangement of a section of the river at the “Myloi Angelopouloi” location, 76.00m long.

For the planning of the projects, an assessment of the supply of the river basin was initially made. After the hydraulic calculations, it was concluded that the cross-section of the existing river was not sufficient to receive the supply in question and due to strong gradients at the location “Myloi Angelopouloi” high velocities are observed. Consequently, intervention projects were required to avoid severe flooding. The demarcation was intended to determine the territorial zone required to ensure as far as possible:

The flood protection of adjacent properties.
The natural form and ecosystem of watercourses and the emergence of autonomous natural formations.
The connection of the zone of watercourses with the urban planning functions of the areas through which they pass and the orderly functioning of the man-made environment.

The proposed projects concerned the creation of an embankment and the lining of the river slopes with wire boxes. Specifically, in a section of about 50 m. it was proposed to maintain the trapezoidal cross-section of the river and arrange it with an unlined bed to accommodate the proposed arrangement works. The bottom configuration would be proposed with 0.30m thick C20/25 concrete. for a length of about 26.00 m. and width from 91.00m to 105.00m.. Before placing the concrete, a 0.10m thick gravel coating was suggested. On both sides, the slopes were lined with wire boxes with dimensions of 2.00 × 1.00 × 1.00 m. (length × width × height) that reached up to the height of the existing bank (left and right banks).