All means of communication comes handy during crisis. Telecom companies and social networking sites have played a major role is locating and coordination rescue and relief efforts.

Social networking giant Facebook has activated its Safety Check feature in Chennai that has witnessed the heaviest rainfall seen in a century.

Facebook, which has its second largest user base in India, activated the feature to allow people mark themselves as “safe” from the floods.

Once the user clicks "Yes, let my friends know", the tool automatically notifies his/her Facebook friends.

Google has also posted a link on its homepage called ’Resources for the Chennai floods’, which provides details about relief camps and updates people about the situation in the city.

People are using platforms like Facebook and Twitter to not just let people know they are safe but also to helping connect people get to safer locations.

#ChennaiFloods remained as one of the top trend hashtags in India on Twitter through the day yesterday.

A website, chennairains.org, has put out a list of places that are offering accommodation and food to people affected by rains.

Telecom operators came forward to help people by offering free talktime and data usage to help them stay connected. Airtel, Vodafone, BSNL, Reliance Communications, and Aircel, are now aiding subscribers in the city with several initiatives.

Airtel subscribers in Chennai will get auto approval for 'talk time' credit up to Rs. 30 (the talk time offer is only for Airtel prepaid subscribers). The company will also provide credit of 10 minutes for Airtel-to-Airtel calls for prepaid customers with a validity of two days. Free credit of 50MB mobile data for Airtel prepaid customers with a validity of two days is also being offered.

For Airtel postpaid and fixed-line subscribers, the company is extending time to make payments whose bills are due to be paid immediately.

Vodafone’s statement said: "To enable Chennai customers to remain connected in this precarious time, Vodafone is offering pre-approved 'chhota credit' of Rs.10 to all pre-paid customers and a credit of 10 minutes for Vodafone to Vodafone calling. In addition, free 100MB mobile data is being offered to all customers. The validity of the talk time credit and free data is two days. For postpaid customers whose bills are due for payment immediately, the time to make the payment is being extended.

State-run BSNL said it will allow free local and STD calls to other BSNL mobile phone users as well as 100 MB data for seven days for its prepaid users. "We have made calls free for pre-paid users in Chennai so that they dont have barrier in their mind of recharging their account in this distress situation. Priority is to enable them stay connected in this situation," BSNL chairman and managing director Anupam Shrivastava said. A rental rebate of seven days and extension of billing cycle by 15 days, it said in a statement.

Similarly, Reliance Communications is offering 10 minutes of all-India free calling and 50MB of data free.

Aircel will offer free 10 minutes Aircel to Aircel calls across India to all its Chennai customers for the next three days. Apart from credit of Rs 30, the operator will also provide 10 Free all India SMS and 100MB 2G/3G free data valid for 3 days.

Paytm is offering Rs. 30 worth of free talk-time to anyone who would like to remain connected.

Practo has a spreadsheet with phone numbers of verified doctors and hospitals available for help in an online spreadsheet. Zomato has launched a scheme where they will provide meals for flood relief victims, and is offering to buy one meal from their end for every one purchased on the website.

Meanwhile, 269 people have died in Tamil Nadu and two in Puducherry since the heavy rain and floods began last month, Home Minister Rajnath Singh told Parliament today. He assured Tamil Nadu of all central help in this "unprecedented situation."

There has been no rain since last night, but the water level has been rising steadily in parts of Chennai. 35 lakes are reportedly flowing at dangerous levels, raising fears of more flooding as surplus water is flowing into Chennai.

"None of the drains can work with such heavy rain. If this kind of rain happens again, we are in for a tough time," said the Commissioner of Chennai Corporation, Vikram Kapoor.

The Saidapet bridge over the Adyar river, which runs through the city, was closed to traffic yesterday as water spilled onto the road. The river is overflowing as surplus water from a lake was let into the river.

The Met office has said the next 48 hours will be crucial and the rains will continue for a week.

The Chennai International airport will remain closed till December 6. The Rajali naval air station at Arakkonam, 70 km west of Chennai, will function as a makeshift airport.

Air India to operate special flight to Arrakonam from Hyderabad to bring back stranded passengers.

Rescue and relief work is being carried out by the army, navy, air force along with NDRF. 11 army columns have been rushed to Chennai.

Prime minister Narendra Modi today conducted an aerial survey of Chennai city.

Water is receding in some parts, but relief and rescue remains a challenge.

Our senior correspondent Shivani Chaturvedi reports
Coastal city of Chennai is now an island. One cannot get out or come in.

Twenty-five-year-old Aaditya is unable to contact his parents in Madurai nor is he able to travel to his parents as the city is cut from rail and road links. 

Native of Madurai, Aaditya moved to the state capital four years back and is working in a private company.

“I have no idea how to go out. I am stuck here,” says Aaditya. “Chennai is floating since yesterday and no concrete steps have been taken by the government. We are struggling for food. Nearby food outlets are closed and we cannot commute to any other locality. There is no water supply. Power supply has been cut off,” he said.

Satyendra Yadav, Munna Yadav and Chotelal Chaudhary are working as security guards in a private company in Saidapet locality. In Saidapet area along river Adyar, more than 2000 huts are submerged. Satyendra, Munna and Chotelal too are unable to reach their family members over phone in Sitamani in Bihar. “This is not for the first time such a situation has arisen. A fortnight back also there was rain havoc. We want to know what measures government has taken to tackle the situation,” asks Chotelal.  

Madras high court advocate Vikraman, a resident of Habibullah road says, earlier water never used to stagnate this way. “The situation is really bad,” he said. “In the name of assisting people, some miscreants are charging passersby Rs 2000 to Rs 3000 for helping them pushing their vehicles through flooded water,” he said angrily. Such instances are pouring in from several parts of the city.

Flooding of the city and the suburbs has been caused by release of water from the reservoirs such as Chembarambakkam, Poondi and Puzhal into Adyar and Cooum that cross the city.