While managing dams and reservoirs, Kerala should opt for an approach that maximises power generation by suitably incorporating weather prediction needs.

This is one of the major highlights of a survey of the damage from the August floods by a team headed by Thomas Oommen, geoscientist and Associate Professor at the Michigan Technological University.

Shutter opening

The survey was carried out by a US-based Geotechnical Extreme Events Reconnaissance (GEER) team funded by the National Science Foundation at various flood and landslide-affected regions of Keala.

It said the opening of shutters of over 35 dams during the peak of the rainfall event had intensified the flooding. Since most of the dams are used for power generation, dam authorities wait till the maximum water level to open the shutter.

Although this approach is ideal to maximise power generation, it needs to be re-evaluated in the context of the August flood damage, the surveyors said.

KS Sajinkumar of the University of Kerala and a member of the team has said that slopes on the verge of collapse, called aborted landslides in Idukki district, could become destabilised and grow into full landslides when another rainstorm strikes.

Monsoon threat

The North-East monsoon is expected and rain spells could reactivate these aborted landslides. Given the danger, it is advisable not to have human habitations in these highly vulnerable areas, he said.

Kerala has over major 45 dams and reservoirs and most of them are used for hydroelectric production. The GEER team only visited two of the dams and was not given permission for photography.

At Idamalayar, the team observed a landslide very close to the dam, which needs to be studied to investigate if it has any impact on the dam’s integrity.

The Kallarkutty dam performed well even though there was news that it overflowed. No signs of visible damage were observed. But the Maniyar dam may have experienced some damage.

There is also visible sign of seepage. These need to be investigated to evaluate the stability of the dam. An Unmanned Aircraft Vehicle-based analysis using thermal and optical sensors may be useful.

As for the Kayal/wetland rice fields in Kuttanad, the floods resulted in the collapse of the ‘bund’ at several locations. The high tide from the Arabian Sea, too, prevented the discharge of flood water.