The inadequacy and inoperativeness of Chennais drainage system was starkly evident in the aftermath of Cyclone Nisha.
CYCLONE Nisha, which accompanied the north-east monsoon and crossed the coast near Karaikal on November 27, left a trail of destruction in Tamil Nadu and the Union Territory of Puducherry. It served as a grim reminder of the floods in 2005, which claimed 150 lives and brought life to a halt in the State for a few days.
The Tamil Nadu government has sought Central assistance of Rs.3,789 crore for carrying out relief and rehabilitation in the flood-hit areas. A Central team of experts visited the affected districts to assess the damage.
Over 39.4 lakh people were affected and 26.45 lakh people had to be evacuated. The government has put the death toll at 186. A total of 3,942 heads of cattle perished in the floods and crops raised over 6.2 lakh hectares went under water. More than 5.7 lakh huts were destroyed and 4.88 lakh partially damaged.
As many as 3,900 relief camps were opened and food packets were distributed to the affected people. The government has announced a relief package for the victims, including a solatium of Rs.2 lakh for the next of kin of the deceased. It has already released Rs.600 crore for immediate relief measures.
Chennai, Tiruvarur, Nagapattinam, Thanjavur, Cuddalore, Tiruchi, Villupuram, Tiruvallur and Kancheepuram districts were severely hit by the torrent. Many parts of the State received excess rainfall (from 6 per cent to 98 per cent) during this post-monsoon or north-east monsoon season, from October 1 to December 3. Chennai received 42 per cent excess rainfall during this period.
As in the past, the Chennai Metropolitan Area bore the brunt of natures onslaught. The release of excess water from Chembarambakkam and Poondi reservoirs and the heavy overflow from lakes and tanks inundated several parts of the metropolis.
Residential, commercial and industrial localities were marooned and went without power for several hours. Public transport was hit with the Metropolitan Transport Corporation and the suburban trains having to curtail their services in the affected areas. Battered roads added to the woes of the public. Telecommunication services and the supply of essential articles such as milk were disrupted. Schools were closed for a few days. Boats were used to evacuate people from the low-lying areas and thousands were accommodated in the schools run by the Corporation of Chennai. Water did not recede in many places even a fortnight after the cyclone crossed the coast.
In fact, Nisha lay as a well-marked low pressure area over north-interior Tamil Nadu and brought more rain. Among the worst affected by the floods and the cyclonic storm were daily-wage earners, fishermen, hawkers and traders in the coastal districts. Fishing was suspended for more than a week in view of inclement weather. Chennai received about 370 mm rainfall in a span of 72 hours, making things difficult for the authorities who also had to tackle the problem of poor drainage.
There is a tendency to identify slum settlements along the water courses in and around city as the main reason for lack of the free flow of water into drainage canals, leading to inundation of adjoining areas and roads in the city.
However, recent studies show that it was not the slums but improper drainage plans that cause the problem. At times, even government-approved layouts and bridges have been important factors contributing to flooding and inundation, say experts.
The inadequacy and inoperativeness of the local drainage system was evident during and after the rain. Heavy waterlogging in several localities apart from the 35 areas known for recurring inundation including Vepery, Basin Bridge, Pulianthope, Vyasarpadi, Chamiers Road and Velachery made the authorities sit up and study the reasons for the pathetic situation.
The Hyderabad-based Aarvee Associates, appointed by the Chennai Corporation, prepared a project report on flood alleviation and mitigation. It cited three reasons for the catastrophic flooding of Chennai: Most of the waterways are silted and their flow channels and banks are obstructed by encroachments and structures. Similar is the case with the reservoirs and tanks. Secondly, several of the areas under tanks and their anicuts have been developed as residential neighbourhoods over the years. T. Nagar, Nungambakkam and Vyasarpadi are instances of this problem. The Taramani area has been developed as an institutional area. Thirdly, the geological structure, particularly on the south-west, is not conducive to water infiltration.
The report recalled instances of such flooding in 1943, 1978, 1985, 2002 and 2005 in Chennai, which were caused by heavy rain associated with cyclonic activity. Particularly, in 2005, 40 cm [of rainfall] in a day caused heavy inundation in Chennai and its suburbs and more than 50,000 persons were evacuated from the low-lying areas, it said.
It also highlighted the problems involved in coastal flooding, which arises from two different sources tidal flooding of low-lying areas owing to strong onshore winds, and strong storms. The high- and low-tide levels for 2008 show that they vary from as low as -0.10 m on March 10 to as high as +1.47 m on November 13. Due to this, the backwaters enter the city, mainly through the Adyar and the Cooum rivers causing backwater curves, it said.
Corporation authorities and officials of the Public Works Department (PWD) referred to the problems related to the maintenance of micro drains (27.92 km) and macro drains (65.92 km) in the city. Though the Corporation claims that desilting of the 16 micro drains, that come under its purview is carried out in two cycles in a financial year, most of these drains were unable to serve their purpose, owing to silt load, entry of garbage through the storm inlets, the level of silt in the storm inlets, illegal sewerage connections and encroachments.
The condition of the six macro drains maintained by the PWD is in no way better than that of the micro drains, though a top official in the Water Resource Organisation of the PWD pointed out that these water courses were desilted well ahead of the monsoon at a cost of Rs.4 crore.
The major waterways the Adyar, the Buckingham Canal, the Cooum, the Otteri nullah, the Virugambakkam canal and the Velachery-Pallikaranai channel which receive surplus water from several tanks and lakes, small streams and rainwater drains in the city and its suburbs often get clogged owing to accumulation of silt and trash at their mouths, which causes stagnation, the consultants said.
The consultants called for steps such as deepening and widening of the canals, putting up flood-protection walls in a few places and removing encroachments.
They have also suggested that tanks and lakes including the ones at Ambattur, Ayappakkam, Ayanambakkam, Korattur, Peerkankaranai, Pallikaranai, Porur and Tambaram in the metropolis be used for capturing flood water.
S. Janakarajan, Director of the Madras Institute of Development Studies, said that the government, even while providing relief to the affected people, should think about long-term and comprehensive measures to reduce the intensity of floods and prevent the damage caused to lives and properties. Stressing the need to protect tanks, he said that encroachment of these water bodies primarily by government agencies and private builders, besides their conversion into dumping yards by the local administration, posed a serious threat. He called for steps such as desilting tanks, strengthening their bunds and clearing their inlet and outlet channels, as the water bodies would enable the administrations efforts to tackle both floods and droughts.
Predicting that large parts of the adjacent districts, Tiruvallur and Kancheepuram, would become part of Chennai city in the next 15-20 years, he said that as many as 3,600 tanks in these districts would be encroached on, levelled and used for non-agricultural purposes in the absence of preventive steps. He said that around 25 per cent of the 39,000-odd tanks and lakes in the State had disappeared in the past 25 years.
Another major reason cited by experts for waterlogging is the re-laying of roads every now and then, and construction of bridges, flyovers and other structures by local bodies and government agencies. These constructions have affected the natural contours that facilitate the surface flow of water. A major challenge is to drain surface water from the city streets with a total length of 2,870 km into roadside drains that have a total length of only 881 km.
On the basis of the consultants report, the State government has submitted a detailed proposal to the Centre, seeking funds under the Jawaharlal Nehru National Urban Renewal Mission to upgrade the infrastructure at a cost of Rs.1538.04 crore. Residents of Chennai and its suburbs have to keep their fingers crossed until the proposal is cleared. For most of them, the thought of another spell of heavy rain is nightmarish.