The Sunday Deep Dive

Cyclone Nivar | How preparedness took the edge off the storm

Mitigating factors: Though the weather system crossed the coast as a very severe cyclonic storm and brought heavy to extremely heavy showers, the amount of rainfall was distributed over three days in various places.   | Photo Credit: K. Pichumani

Since December 2015, Chennai residents have lived in fear of a monsoon crippling life as they know it. For the residents of northern Tamil Nadu, it was the memory of Cyclone Thane; for the Cauvery delta region, that fear was evoked after Cyclone Gaja; and for southern Tamil Nadu, it was Cyclone Ockhi that put the fear in people’s minds. Over the last few years, Tamil Nadu has suffered much from the assault of weather systems. In contrast, last week’s Cyclone Nivar seemed far less destructive. Nivar that made landfall near Marakkanam in the early hours of November 26 did leave parts of the State under water, causing damage to lives and property. But the impact was minimised not only because of the way the storm blew but also as because government agencies and disaster management teams were better prepared.

Also read: Data | How lesser rainfall, reduced inflows & measured water release from Chembarambakkam blunted Cyclone Nivar's impact

The experience from the past cyclones, however, formed benchmarks for the government agencies to build better coordination, chalk out plans and implement a portion of the long- term flood mitigation projects.

Though Cyclone Nivar crossed the coast as a very severe cyclonic storm and brought on rains of heavy to extremely heavy intensity, the amount of rainfall was distributed over three days in various places along the coast and interior places.

The Tamil Nadu government had deputed senior IAS officers and Ministers to coordinate preparatory measures like shifting of people from low-level and vulnerable areas to safer places, mobilising equipment and taking post-landfall measures along with the Collectors. the India Meteorological Department’s frequent alerts and precise forecasting of the landfall helped local bodies and residents prepare for the cyclone.

While rainwater did flood vulnerable localities of Chennai owing to the incessant rain that started two days before the landfall, residents noted that desilting of minor waterways and stormwater drains by the Greater Chennai Corporation helped to prevent waterlogging in parts of the city that are usually flooded.

But highly vulnerable areas such as Mudichur, Varadharajapuram and parts of West Tambaram were surrounded by sheets of water. Heavy rain of 31 cm at Tambaram on November 26 added to the woes. While it was not like 2015, residents noted that some projects were executed in the southern suburbs. But these areas need a permanent solution to inundation in subsequent monsoon cycles.

Admitting that only 30%-40% of the interventions were able to be implemented, officials of the Water Resources Department said the surplus of four tanks come together on the Varadharajapuram stretch of the Adyar. “We have improved the capacity of culverts in these low-level areas, but need to develop infrastructure and deal with encroachments. We have chalked out projects costing ₹3,000 crore and await World Bank funding,” said an official.

Meanwhile, the 2015-like calamitous flooding of the Adyar and the Kosasthalaiyar was avoided as the government decided to allow measured water release from the Chembarambakkam and Poondi reservoirs during and after Cyclone Nivar. Anticipating additional inflow and rains, the Water Resources Department regulated the release according to the flow received at two-hour intervals. This gave sufficient time for the river to carry the water without spillover.

Building flood regulators, desilting of waterbodies upstream of the Chembarambakkam reservoir and the Adyar and emptying small amounts of water from lakes ahead of the cyclone helped in mitigating floods and store more than 500 million cubic feet (mcft) of water in lakes in the Adyar basin. “Nearly 2,000 mcft was drained into the Adyar. When the ongoing works to build a reservoir and check-dams in the Adyar basin are completed, we will be able to save 1,000 mcft,” the official said.

However, experts noted that if the Chembarambakkam reservoir had been properly desilted, the water release could have been avoided or delayed even further. While appreciating the move to maintain storage space in the lakes, L. Elango, Professor, Department of Geology, Anna University, said, “We had recommended that the Chembarambakkam lake be deepened by one metre greater than its original capacity to enhance its storage.”

He also elaborated on the proposal to carry water from the Chembarambakkam reservoir to Sikkarayapuram quarries that began to be used as storage structures for the city’s water supply. This could be done during floods and droughts to prevent loss.

Research scholar Rinisha Kartheeswari said the excess water could be transported through a combination of a two-km open channel and pipelines. Similar arrangements could be made to convey water to quarries at Erumaiyur and Tiruneermalai.

But WRD officials said they need at least eight years for carrying out the entire desilting exercise. Only 20% of desilting could be done in the Chembarambakkam lake within the limited time available, they said.

Outcomes of competitive politics

In the hamlets of the Union Territory of Puducherry and the adjoining Tamil Nadu districts of Cuddalore and Villupuram, hectic activity started in the coastal villages a day ahead. This helped to reduce the impact. As per the advice of the Fisheries Department, people shifted boats and nets from the shore. Boats anchored at the harbours were tied to prevent damage by heavy winds. “Evacuation of fishermen to safer places is usually challenging. But this time, there was not much reluctance,” said an official of the Revenue Department.

While law enforcement agencies opined that the damage would have been more had the wind speed been at its maximum, officials of the meteorological department confirmed that winds lashed at 120 kmph at the time of the landfall. The meteorological department was collating reports on the extent of destruction. “It may have passed through uninhabited places or salt pans where damage is not immediately known,” said an official of the meteorological department.

Weather expert Y.E.A. Raj said, “The system moved rapidly inland after making landfall. This could have reduced damage, unlike the previous cyclones. The type of vegetation and housing it encounters also matters.”

Preparedness was the key to the fact that no lives were lost in the Union Territory, officials said. Section 144 of the Code of Criminal Procedure was invoked in the Puducherry and Karaikal regions to curtail the movement of people. Meetings and frequent visits by Lt. Governor Kiran Bedi and Chief Minister V. Narayanasamy put the officialdom on its toes.

Apart from the assistance of the NDRF, 100 personnel from the Army’s humanitarian assistance and disaster relief unit were deployed for rescue operations. Pruning of tree branches limited damage. The low-level areas were flooded again.

The Tamil Nadu government was quick to depute Principal Secretary Gagandeep Singh Bedi to Cuddalore to assist the Cuddalore district administration, which had identified 278 vulnerable areas and cleaned up stormwater drains. The Villupuram administration focussed on evacuation of people from Boomayarapalayam, Kottakkuppam and Marakkanam. Police presence ensured that fishermen did not stay near the shore during the landfall.

Emergency response

Disaster management teams were prepared to face nature’s fury on the scale of Cyclone Gaja and NDRF teams were positioned hours before the cyclone hit the coast. They stepped in to clear the roads of fallen trees, electric poles and cables.

Revenue and panchayat workers were present in the villages on the night of landfall and made better arrangements than what were in place during Cyclone Gaja, said R. Perumal of K. Gudalure near Kollidam on the borders of Nagapattinam and Cuddalore districts.

The efficiency of rescue and relief measures would have brought back normalcy in a few days had a cyclone of the velocity of Gaja struck in Nagapattinam. Within a day of holding a review meeting, teams of the Revenue, Police and Rural Development Departments shifted 59,171 people to safe places. “We were particular about preventing destruction and bringing back normalcy quickly. We believe we have achieved them,” Nagapattinam Collector Praveen P. Nair said.

(With inputs from Rajesh B. Nair in Puducherry and C. Jaishankar in Nagapattinam)

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Printable version | Jan 27, 2021 1:13:21 AM | https://www.thehindu.com/news/national/tamil-nadu/how-preparedness-took-the-edge-off-cyclone-nivar/article33205602.ece

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