The absence of comprehensive disaster vulnerability mapping for the 426 sq km of the city remains a major lacuna, especially for localities vulnerable to disaster.

Even though the tsunami alert on Wednesday facilitated the mobilisation of official machinery in the 29 coastal wards of the Chennai Corporation, councillors and ward-level officials in these areas said that data on reliable escape routes and the number of dilapidated structures prone to disaster had not been supplied to them.

According to disaster management experts such as N. Mathavan, who have worked on preparation of disaster resilience indices for the old city limits, the need for data on the disaster vulnerability of each of the 200 wards in the expanded Corporation limits is high, because around 90 lakh lives in and around the rapidly urbanising area are at stake. “The local community and officials should know the safest escape route in case of a disaster. They should be informed of dilapidated buildings that may collapse and the nearest hospitals for rescue operations. Comprehensive disaster vulnerability mapping will be a tool to help the community cope with disaster,” said Mr. Mathavan.

According to Corporation officials, unauthorised development and the lakhs of old buildings near the coast are yet to be documented to create awareness among ward-level officials.

The Tamil Nadu Slum Clearance Board has also been unable to work out a reasonable rehabilitation package for a chunk of the residents who reside in dilapidated tenements.

Associate Professor of Madras University Department of Applied Geology R.R. Krishnamurthy said data on inundation of coastal areas during the tsunami in 2004 was collected. But the livelihood concerns of many fishermen on the coast were said to be the reason for the continuous existence of disaster-prone residential areas in areas such as Sholinganallur, Injambakkam, Neelangarai, Palavakkam, Kathivakkam, Srinivasapuram, Thidir Nagar, Marina Beach and the Pulicat mouth area.

The absence of comprehensive disaster vulnerability mapping is also a hindrance towards creating awareness among residents on the need for quick evacuation.

“When officials announced the tsunami alert on Wednesday, over 50 per cent of people near the coast were reluctant to leave their homes. We had to repeatedly warn them to take them to a safe place,” said councillor C. Munusamy of Neelangarai.

Had the tsunami struck on Wednesday, the civic body would have found it tough to tackle the challenge posed by the disaster. The Chennai Corporation joined a ‘Safe Chennai Campaign' launched by the United Nations International Strategy for Disaster Reduction on August 19, 2010. But many of the 10-point programmes are yet to be realised.

The civic body has already done a seismic vulnerability mapping under a sub-component of the Government of India-UNDP Disaster Risk Management programme a few years ago. But data on disasters such as cyclones or tsunamis is yet to be furnished due to a lack of coordination among various departments.

The comprehensive disaster vulnerability mapping would also use data pertaining to vulnerable groups including pregnant women, babies, persons with disability and the elderly. This would enable the civic body to focus on streets or households which require more attention in times of disaster.