Environment

Assam’s Updated Flood Hazard Atlas Helps Categorise Vulnerability of Each Village

The National Remote Sensing Centre has also been approached by the state for a satellite image based altas of hazard prone areas in terms of agriculture and population.

A flood affected village of Murkata in Morigaon district of Assam. Credit:PTI

A flood affected village of Murkata in Morigaon district of Assam. Credit:PTI

New Delhi: For decades, the state government of Assam has dealt with the annual floods with only a standard approach of relief and rehabilitation of the affected. However, it has not used any scientific methodology to study the spread and impact of the floods to help address it better.

In 2011 – for the first time in the country – the Tarun Gogoi government approached ISRO’s National Remote Sensing Centre (NRSC) in Hyderabad to develop a satellite image based flood hazard atlas for the state in order to help district officials better link the various schemes and measures taken for the vulnerable areas.

On September 6, NRSC updated the state’s atlas after the Sarbananda Sonowal government approached it for the job.

Once again the state has become the first in the country to not only have an updated version of such an atlas, but also to have one that has images of all the villages in the 35 districts over a span of 18 years (1998-2015).

With the help of 215 images, the villages have further been categorised into five types based on their inundation levels. The categories are – very high, high, moderate, low and very low.

Flood hazard map of Assam. The different colours represent different hazard types. Credit: ISRO

Flood hazard map of Assam. The different colours represent different hazard types. Credit: ISRO

Released by the state’s revenue and disaster management minister Pallab Lochan Das in Guwahati, the atlas has scientifically established that 17 of the state’s 35 districts have been severely affected by floods over the past 18 years. According to ISRO’s website, “About 28.75% (22.54 lakh hectares) of land in Assam state is affected by flood during 1998-2015.”

Release of the updated Flood Hazard Atlas for Assam state by Pallab Lochan Das. Credit: ISRO

Release of the updated Flood Hazard Atlas for Assam state by Pallab Lochan Das. Credit: ISRO

Biren Baishya, the head of Geographic Information System at Assam State Disaster Management Authority (ASDMA), which validated the maps for NRSC, told The Wire, “The data analysis of 18 years has shown variations. For instance, some villages categorised as very high are seen to have gone under moderate or high category, while some others under moderate category have now gone to the high category.”

Looking at the scenario post 2011, Baishya said, “Prior to it, the district officials were haphazardly using the government schemes and other projects meant for vulnerable areas. With the help of the atlas, they got a direction to link better the schemes in the most affected areas to lessen the impact of floods.”

Since the atlas “was of a bulky A3 size,” he said, “ASDMA broke it further into thin brochures, district-wise, for better usability. We also incorporated various suggestions to the district authorities on how to handle better the crises springing out of flood situations.” Later, NRSC made a similar atlas for the flood affected Bihar too.

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Satellite images showing the normal and flood conditions (below) at Kaziranga National Park in Assam. Dark colour indicates water in these images. Credit: ISRO

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Baishya said that the latest updated atlas – even though it doesn’t include this year’s floods – is said to be one of the worst in years and, “will further help us improve the official response to floods.”

“In fact, the government has plans to go a step further. ASDMA has already written a letter to NRSC to tailor for us a satellite image based altas of only the hazard prone areas in terms of agriculture and population. With such a specialised atlas, we will be able to adapt the preventive measures much better,” he said.

“Since this atlas will again be a first for the NRSC, it is working on a methodology for it.”

(The Wire is awaiting a response from state disaster management minister Pallab Lochan Das at the time of publishing.)