Unprecedented Kerala deluge that swept through the coastal state on the day of Independence day 2018 was most disastrous flood incident in the year. It has also been termed as one the worst flood in the state and reminded the people of July 1924 and July 1962 flood calamities. Many experts, several reports and studies have established the role of dams in worsening the deluge. According to reports, 35 out of the 46 dams within the state were opened for the first time in history. All 5 overflow gates of the Idukki Dam were opened at the same time, for the first time in 26 years.
State Government Accepts Dams Role
Kerala is usually considered a flood-proofed state with its undulating terrain. For a state that receives an annual average rainfall of nearly 3,000 mm, its natural landscape protects it from recurrent floods. Indeed, the Kerala flood has highlighted our poor dam management system.
As per officials the crisis could have been contained had the state “gradually released” water from at least 30 dams, in advance of high rainfall, adding that local authorities failed to foresee the imminent danger with high rain predictions. “Such floods have probably recurred after 100 years, exposing the State’s unprofessionally run reservoirs management system and unpreparedness on disaster mitigation and disaster resilience.
According to a serving KSEB engineer, there was absolutely no need to hold water in Idamalayar dam till August 9 as the KSEB knew that this dam gets filled fast. Similarly, more water should have been released from Poringalkuthu dam from August 1 onwards, if not earlier to get it ready for water from Sholayar dam in Tamil Nadu.
Ironically, even as the people of Kerala watched the water from Cheruthoni (Idukki) dam tumbling down the Periyar river on August 10, on television, the authorities did not have an idea on how much it would flood in Aluva and how high would the water rise.
PH Kurien, Kerala’s head of disaster management said that he has twice written to KSEB requesting Emergency Action Plans (EAPs) and has yet to receive them. According to a KSEB official EAPs and dam operation manuals were still being prepared. CWC said it was working with Kerala’s government to speed this up.
Surprisingly, KSEB authorities, in stead, began discussions regarding construction of a new hydroelectric power plant as part of Idukki dam. The govt has also pushed its efforts to introduce rubber check dams in the state.
Central Government Confirms Unscientific Operation
In a candid revelation Madhavan Nair Rajeevan, Secretary, Ministry of Earth Sciences said that Kerala state did not have a flood warning system in place and dams in country lack scientific methods to manage the flood.
As per an India Meteorological Department (IMD) officials the rainfall was extremely heavy; however, the IMD had predicted that the extremely heavy rainfall was very likely and the state should have taken the decision to release water from the dams that were almost full when the rains had subsided in late July and early August.
In acknowledgement of a major fault of Kerala dams, the Central Water Commission (CWC) September 2018 report recommended revisiting the ‘rule curves’ — strategic water level for planning operations of a dam — of all reservoirs.
A rule curve specifies storage or empty space to be maintained in a reservoir during different times of the year. Rule curves are derived by studying historical data. Unfortunately the dam operators in country are not following rule curves.
According to Sharad Chandra, CWC Director of Flood Forecast Monitoring, CWC had received no proposal regarding flood forecasting station from Kerala. The CWC has 22 flood monitoring stations in Kerala. He said that, untimely and sudden releases from the reservoirs in Kerala should not add to any flood situation in future.
Prof Narendra Kumar Goel at the Department of Hydrology at IIT Roorkee suggested the use of Flood Forecasting System in Kerala. Corroborating SANDRP, he also said that if FF had been undertaken, then this disaster could have been reduced. He also advocated making optimum use of existing dams rather than going for new ones.
Some Dam Breach and Damage Incidents
The Moolathara Dam on Bharathapuzha river breached submerging few bridges and crops near Chittur and flooding Chitturpuzha and Bharathapuzha on August 9. This was the 4th time the right bank protection structure of the dam, part of the inter-State Parambikulam Aliyar Project, had breached. The earlier instances were in 1960, 1979, 1992.
Kerala State Electricity Board (KSEB) was held responsible for not following Standard Operating Procedures before raising all the four shutters of the Banasura Sagar dam on Kabini river on Aug. 8, 2018 which resulted in worsening of the flood situation in the Wayanad district.
Concerns were also raised that the impact of the opening of the Idukki dam could have been minimised if the shutters of Idamalayar dam were opened earlier. For only the third time since the Idukki dams system was commissioned in 1975, one of the 5 shutters at Cheruthoni was opened August 9. On both earlier occasions, the Idukki dam was opened in October, during the northeast monsoon. This was the first southwest monsoon when the dam gates were opened, and when the Idamalayar dam too, had been opened.
Dams Did Not Follow Rule Curve Monitoring the situation since beginning SANDRP was possibly the first to reveal that major storage dams like Idukki and Idamalayar, released water when the downstream areas were facing floods and thus added to the flood misery. It was invitation to disaster that dams were filled to edge in the middle of monsoon grossly violating the rule curves.
The rainfall was unusually high but if the dams were operated properly, the scale of the disaster could have been much less. At the invitation of National Institute of Disaster Management of Union Home Ministry, speaking on ‘Reservoir Operation and Flood Risk Management’ in the context of Kerala, Himanshu Thakkar, SANDRP said that it was “not good enough” if authorities made the argument that outflows from dams equalled the inflow during floods.
In Economic and Political Weekly, (Vol. 53, Issue No. 38) SANDRP explained that during the July–August 2018 floods in Kerala, basic norms were violated in the management of dams, which, if operated prudently, could have alleviated the magnitude of the disaster. In this context, a strategy for the management of dams to mitigate similar disasters has been outlined.
STUDIES The CWC study stated that dams in Kerala neither added to the flood nor helped in reduction of flood however it accepted that many of Kerala’s major dams were filled to the brim even ahead of the torrential rain in August highlighting that the state of dam management in India and its role in exacerbating the damage from floods. Further, in their analysis SP Ravi, K J Joy, Neha Bhadbhade found that CWC is wrong in denying a link between dam releases, reservoir levels and the floods.
Another study by scientists at IIT Gandhinagar and IMD included reservoirs mismanagement a reason behind Kerala floods among others. The results of the study were posted on September 14 in Hydrology and Earth System Sciences Discussions, and the manuscript is being peer-reviewed.
The research by Jawaharlal Nehru University’s Special Centre for Disaster Research, in collaboration with the National Institute for Disaster Management, also identified several points of govt. failure that ostensibly contributed to the devastating magnitude of the flood and its consequent destruction in Kerala this year.
EXPERTS Well-known ecologist Madhav Gadgil, described the devastating floods in Kerala as a man-made disaster and a reaction to the illegal excavations and stone quarrying done over a decade. He also said that the efforts to rebuild the state must not be undertaken in a bureaucratic manner, but must be opened up and must be undertaken at the grass root level.
According to Prof Ashok Keshari of IIT Delhi, the flood damages could have been reduced by 20-40% had the dams and reservoirs released the water slowly in the two week period when the rains had subsided. M. Gopakumar Executive Director, Nityata River Otter Conservancy said that the tragedy has highlighted the dangers of excess water accumulation in dams and India’s policy on dams has to be urgently reviewed.
According to J Letha, vice-chancellor Cochin University of Science and Technology, a proactive approach for the effective monitoring of sophisticated climate technology, dam monitoring systems, and the application of radar facilities would have definitely mitigated the disastrous flood. She also said that effective management of dams should be ensured in future and it should be considered while planning the rebuilding of Kerala.
In his article, Narayan Ramachandran chairman, InKlude Labs wrote that dam management has been very engineering-oriented in its approach, with dam safety and reservoir heights emphasized over a more holistic and integrated approach that would include weather simulation, land use on the flood plain and community preparedness. For dams to do their jobs in extreme situations, they should have large unfilled capacity in their reservoirs when extreme events occur.
NASA scientists also claimed that the floods in Kerala were worsened by uncoordinated water release from almost overflowing dams. According to the space agency, authorities were forced to open many dams including Idukki, when they should have instead gradually released water before the floods. NASA on August 26 released an interactive graphic which showed the extent of flooding in parts of Kerala.
Indeed, the tendency to store water to almost the full level of reservoirs is becoming a norm among water managers across States. In mid-July, Karnataka, too, started releasing surplus waters from the Kabini and Krishnaraja Sagar dams on the Cauvery system only when it knew that it could not hold any more water.
Fortunately, the Mettur dam in the Salem district of Tamil Nadu had space to accommodate the flood flows. For the last one month, Mettur too, has been releasing excess water flows. In December 2015, Tamil Nadu also faced criticism from CAG for delaying the release of surplus water from the Chembarampakkam tank, causing floods in Chennai.
As per Himanshu Upadhyay faculty at Azim Premji University, Bangalore, a table in the CAG performance audit report shows that out of 61 dams, none had Emergency Action Plan or Operation and Maintenance Manuals. Kerala had also stated, in response to audit query from CAG of India, “No dam-break analysis was conducted in respect to any of the 61 dams in the state.”
HUNGRY WATER, SILTATION, SAND MINING, FLOODPLAIN ENCROACHMENT 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.
Hungry water can also develop in high gradient river channels devoid of adequate quantity of sand and gravel, especially during periods of high rainfall. Dr. Padmalal asserts that the hungry water effect has had a major stake in the flood hazards in areas close to Kerala dams like Ranni.
As per a senior engineer KSEB, assessment of siltation of Kerala reservoirs is required as large-scale deposits of silt caused by the recent floods have severely affected the storage capacity of many reservoirs, including the Idukki reservoir.
A study earlier in the catchment area of Idukki dividing it into eight zones showed that the Upputhara-Ayyappancoil stretch and Kulamavu area were highly prone to silt deposits due to large human habitations and loose soil.
“However, for nearly 10 years, no study on silting was undertaken,” the official said adding a behavioural study on the dam should be conducted in the wake of the flooding that resulted with the opening of the vents of the Cheruthoni dam.
In some cases, when a reservoir is constructed on a river, filter dams to prevent silting are constructed. In the case of Idukki, no filter dams are in place though four rivers are diverted to the reservoir. This also causes more silting in the reservoir.
As per India Water Portal report, one reason for the unprecedented flood of such magnitude is unplanned construction and encroachment on riverbeds that have reduced the capacity of rivers to carry flood waters. The lack of regulation and enforcement of land use in the floodplains added to the severity of the damage. “Yet the recent report by the CWC on Kerala floods does not say a word about rampant riverbed and floodplain encroachments,” says Himanshu Thakkar, coordinator of SANDRP.
The Ganga Today editorial also mentions that encroachments of riverbed has also attributed to flood fury as this has reduced flood carrying capacity of rivers. The loss from the floods may be much more than the benefits from bridges, hydropower projects, irrigation and expansion of the residential areas. Therefore, the Govt should take steps to preserve the riverbeds in entire country.
According to PH Kurien, the floods have given a reality check on what happens when houses are built on water bodies and this is the right time for the Govt to come out with a progressive land use policy. Similarly a comprehensive article by Damyanati Dutta reveals how unabated illegal sand mining contributed in turning the floods into disaster.
Kerala Flood 2018: The Human Story Discovery Documentary The Discovery Channel documentary on the Kerala Floods paints an interesting picture of the Kerala floods and people’s response to it.
DROUGHT AFTER FLOODS Within a month of severe floods, the state is reportedly facing the drought threat. According to Thomas Oommen, Associate Professor, Michigan Technological University, floods had impacted the topography and contributed to the possibility of riverbed scouring. The August floods in Kerala resulted in high flows in all the rivers. Such high flows led to excessive riverbed scouring.
In addition, the opening of a number of dams caused high flow in the downstream channels making them vulnerable to scouring. According to Oommen, the scouring and deepening of riverbeds will lead to lowering of the groundwater table along a river, which can cause a drop in the level of water in wells and dry out vegetation on floodplains.
Kerala Govt accepts need for depletion of water in dams in advance of rains It is great to see, Kerala irrigation department is waking up to need for better reservoir management but KSEB also needs to follow. An expert panel that looked into the safety of dams and barrages in the state has recommended for hydrology studies to fix the maximum water level in the dams.
In a welcome change, Kerala depleted reservoirs in early October in anticipation of deluge from Cyclone. It is refreshing that Kerala now accepts needs for better operation of dams with IMD red alert in Idukki, Palakkad and Thrissur districts.
In view of the IMD’s prediction of heavy rainfall in the district till October 6, the shutters of the Mattuppetty dam were opened and warning issued to those living in Munnar, Muthirappuzha, Kallarkutty and Lower Periyar. 4 shutters of the Malampuzha dam were to be opened owing to the heavy rainfall expected in the Palakkad district from October 5.
The Kerala State Disaster Management Authority (KSDMA) also requested the CWC to issue directions to Tamil Nadu to open the shutters of all dams under their control in the state in advance given the heavy rainfall forecast by the IMD.
KSDMA also asked the state water resources department and KSEB to submit a water control framework with regard to the dams under their control considering the current level, long-term storage and rain forecast. Executive engineers controlling dams were asked to keep in touch with district collectors and not to open the shutters without the permission of the district administration.
Compiled by Bhim Singh Rawat, SANDRP (email@example.com)