THIRUVANANTHAPURAM: The rapid environmental impact assessment (EIA) of the SilverLine, part of the detailed project report (DPR), has identified 538.88 sqkm of watershed areas along the proposed line as ‘highly prone to flooding’. As many as 25 points like Murukkumpuzha in Thiruvananthapuram and Kattachira in Kottayam fall under different hydrological environment impact zones.
These regions are highly prone to flooding with streams crossing the path. The EIA recommends that appropriate cross drainages — bridges, culverts or viaducts — should be constructed along the region to avoid risk of floods. However, no bridge or viaduct is proposed to be built in these regions.
The proposed line runs adjacent to the coastal belt for a major portion of the alignment. The rapid EIA has not covered tsunami/tidal effects and has recommended that proper studies should be done during the preparation of a comprehensive EIA.
Similarly, the alignment passes through flood-prone areas throughout and sand piping-prone areas in Kasaragod taluk. (Sand piping is a hydraulic process that leads to the development of large, air-filled voids in the subsurface that are associated with landslides).
In addition, it passes through storm surge/tsunami inundation areas in Malappuram, Kozhikkode and Kasaragod districts. “Sufficient design parameters should be included to overcome any eventuality of storm surge damage or damage due to tsunami inundation,” the report said.
The hydrologic impact assessment shows Kollam station and yard are proposed on flood plain. The Kollam station and Kollam, Kasaragod yards will have ‘very high’ (flood) impact, while Chengannur and Kottayam stations will have ‘high’ impact.
The report proposed to realign and divert the Ayathil stream in Kollam. “The Ayathil thodu with a catchment area of 15.3 sqkm and flood discharge of 25 m3/sec is running along the rail-line. The ‘thodu’ is required to be realigned and diverted for the development works. It is, therefore, seen as the most vulnerable place of hydrological impact,” the report reads.
EIA poposes to divert Ayathil thodu
In Kollam, the station and yard area are proposed on paddy fields and flood plains. The Ayathil thodu runs parallel to the proposed line and discharges flood waters from its catchment area of 32.73km. For the proposal to materialise, the stream and its tributaries should be deviated through the boundary.