The tendency of filling up reservoirs in the beginning and middle of monsoon season have been leading to avoidable flood disasters in the country. Apart from Kerala flood 2018, which was aggravated by mismanagement of reservoirs, various reports show that reservoirs in river basin of Cauvery, Krishna, Godavari and Ganga were also filled up well before the end of South West monsoon season. Resultantly there were many man made flood spells in downstream areas affecting lives and livelihoods of people.
After highlighting role of dams in floods in Kerala and how improper dam operation affected people in Assam and Himachal Pradesh, this third and concluding part throws light on other dam induced flood (and canal breach) incidents in 2018. Continue reading “Dams Floods 2018: Filling up Dams well before Monsoon end, Invitation to Disaster”
Dams and reservoirs make rivers sediment-starved and menacing manifold downstream. While heavy rainfall is also a key factor behind the floods, hungry water had a more pronounced effect, says D. Padmalal, Scientist and Head, Hydrological process group, National Centre for Earth Science Studies.
– “When the sediment transport is interrupted, the potential energy of the hungry water released from dams will scour the river banks downstream, uprooting trees or riparian vegetation and damaging bridges and other engineering structures,” explains Dr. Padmalal. Overloaded with silt and clay from the eroding river banks, the highly turbid and viscous water clogs drainage channels. Subsequent discharge of water from the dam will lead to inundation and waterlogging of large areas.
– Hungry water can also develop in high gradient river channels devoid of adequate quantity of sand and gravel, especially during periods of high rainfall. “Years of uncontrolled sand mining have left most of the rivers in Kerala depleted or exhausted of sand and gravel. This creates a situation similar to the release of hungry water from dams,” notes Dr. Padmalal. When the river channel has adequate supply of sand and gravel, the potential energy of the water is used to transport the mixture. The water does not scour the banks or turn muddy.
Continue reading “DRP News Bulletin 1 October 2018: Hungry Water Effect due to Dams & Unsustainable Sand Mining Worsened Kerala Floods”