Thiruvananthapuram: An alert on tidal flooding of the Indian coastline for September 25-30 has been sounded, including for low-lying areas in coastal Kerala.

The warning by the Indian National Centre for Ocean Information Services – an autonomous body under the union ministry of earth sciences – says the flooding is likely to occur due to perigean spring tide (also called supermoon or king tide).

Coastal communities and others have been warned of possible tidal flooding along the Indian coastline and other locations (including islands like the Maldives) in the Indian Ocean, apart from low-lying areas in southern Kochi, Alleppey, Kollam and Thiruvananthapuram along the Kerala coast.

The tidal currents would be maximum during this period. Distantly generated swells, wind waves and heavy local river discharge could compound the flooding effects, the warning said.

These effects are likely to be more during September 28-30.

‘Supermoon’ is a perigean spring tide that occurs on new or full (syzygy) moon when closest to the Earth (perigee), causing increased tidal ranges or increased current speeds than experienced during the normal spring tides.

It occurs three or four times a year when the Moon’s perigee (its closest point to the Earth, during its 28-day elliptical orbit) coincides with a spring tide (when the Earth, the Sun and the Moon are nearly aligned every two weeks).