Short duration high intensity rains bring more water: Dr S Manivannan

Ooty: While heavy rains pounded Nilgiris for the past three days, there was no major landslide reported in the hills, except for one at near the hydro-power generation station at Avalanche and another one at the hydro-power generation station limits at Kattukuppai area near here.

What is the reason for this? Whether the slopes took care of the rainfall and fed the reservoirs below or any other reasons?

For this, Dr S. Manivannan, principal scientist at the Indian Institute of Soil and Water Conservation and Research Centre, here, said that sudden high intensity rains for a short duration hardly triggers landslides of higher magnitude, though, it may trigger minor landslips and mud-slips along the road sides and fragile slopes.

 “When there is medium intensity of rainfall for a longer duration, coupled by high intensity torrential rains at intervals generally cause landslides.  But, this time in Nilgiris, the SW monsoon rainfall was scanty over June and July leaving the sub-soil surface nearly parched.  If the landslides were to be triggered, the continuous rains over a week should soak and weaken the soil so as whenever there is heavy downpour, the soaked soil mass will come down as landslide.  The heavy rains now only results in heavy flow of water that runs down the slopes,” he explained.  

However, he cautioned that if the present heavy rains continue for some more time it may trigger landslides.

The heavy rains in short period of time bring more water.  But, what is needed is timely de-silting of all water bodies and reservoirs to increase the capacity of sto-rage, he pointed out.