The century-old Mullaperiyar dam may be hydrologically unsafe but there are many options available for reducing its disaster risk.
The observation comes from Dr A.K. Gosain, Professor and Head of Civil Engineering Department, Indian Institute of Technology (IIT), New Delhi.
PMF METHOD
Dr Gosain was here to make a presentation on ‘Estimation of PMF (Probable Maximum Flood) to evaluate safety of dam — A case study.'
The PMF method is applied to check the adequacy of the spillway of an existing dam or to design the spillway of a new dam by diverting water through the reservoir.
Dr Gosain constructed the PMF model for the Mullaperiyar dam by simulating the diversion of flood waters when reservoir level is low, medium and full.
‘BAD NEWS'
“We found that in all the cases, the level was beyond the top of reservoir. For a few hours, ranging from 8-14 hours, the water level exceeded the maximum of 158 feet.
“This is bad for any dam and we came to the inference that the Mullaperiyar dam is not hydrologically safe,” Dr Gosain said.
The study and findings conducted around two years ago were shared with the State Government.
Dr Gosain's presentation on Mullaperiyar was made at the recently concluded international workshop on disaster risk reduction and contingency planning.
Available OPTIONS
On the options available, he said whenever a flood occurs, some portions of the flood can be accommodated by releasing water from the reservoir in advance. Another option is to find a mechanism for withdrawing more water from the reservoir or by creating a bigger spillway.
Alternatively, the dam can be replaced with a better structure.
On the question of potential threats to the dam in event of an earthquake, he said there are options to strengthen the dam by retrofitting.