Experts warn Kerala of more landslides as quarries blast off Sahyadri
22 October 2018
With rock quarries and sand mines shaking the very foundations of the Sahyadri mountain ranges in Kerala, experts have warned of increasing landslides across the eastern flanges of the state that borders Tamil Nadu, spreading destruction to the neighbouring states as well.
While this is the case with almost all states in the country it is more acute in Kerala where landslides combined with unscientific management of dams and reservoirs made things worse, causing the worst flood in a century in August this year. .
Experts say that while an approach that maximises power generation is good, states like Kerala that gets abundant rains, should suitably incorporate weather prediction in dam management.
In fact, it is the lack of a calibrated approach to dam water release that resulted in the August floods, says the experts say highlighting a survey of the flood damage.
The study by a team headed by Thomas Oommen, geoscientist and associate professor at the Michigan Technological University, say 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.
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 Kerala.
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 said the slopes on the verge of collapse, called aborted landslides in Idukki district, could become destabilised and grow into full landslides when another rainstorm strikes.
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 more than 45 major 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.
In Kuttanad, the floods resulted in the collapse of the ‘bund’ at several locations resulting in the submergence of the Kayal/wetland rice fields. The high tide from the Arabian Sea, too, prevented the discharge of flood water.