How tweets turned into flood maps can help save lives

Spontaneous tweets about major floods are being turned into a mapping tool that could be used by emergency services and disaster response teams to save lives and provide aid, Dutch researchers said.

When a crisis strikes, people increasingly find out about it from social media, as individuals and groups take to the internet to spread the word.

After the Indonesian capital Jakarta was hit by floods this February, related tweets peaked at almost 900 a minute, with a significant number including information about location and water depth, according to a joint study by two Dutch organisations, Deltares and Floodtags.

The team then analysed the thousands of tweets – and others from similar flooding a year earlier – to derive a method for creating real-time flood maps based on Twitter messages, statistics and data on land elevation and water motion.

“This method is really fast,” Deltares flood expert Dirk Eilander told the Thomson Reuters Foundation. “It can produce a map within around a minute of messages being posted.”

Jakarta has some gauges that measure water levels, but there is no network that can give an overview of flooding street by street. Many tweets, on the other hand, contained detailed information about how many centimetres deep the water was at particular spots, Eilander said.

Because observations by ordinary people tend to be rough estimates, the data need to be filtered, enriched, validated and transformed into easily interpretable maps that can be used by disaster managers.

When the researchers compared their results with photographs of the Jakarta floods at more than 100 points, they found they had modelled the floods correctly in around two thirds of them and in three quarters of districts.

“Although there is still some room for improvement, these maps are very useful information for emergency services to … find the people who are affected or to plan for evacuation routes,” Eilander told journalists at a geosciences conference in Vienna where the research was presented on Tuesday.

The maps could also be used to help speed up recovery work after a disaster or to identify flood-prone areas that would benefit from protection, Eilander added.

The project has yet to be put into practice to support flood response, but there are plans to disseminate the information via the Floodtags website. Floodtags is a social enterprise that uses social media to monitor floods.

Analysis is also being carried out on tweets about floods in Serbia.

Deltares, an independent research institute, said the method could be scaled easily for any place in the world with enough Twitter activity – most likely in urban areas where there tends to be a high concentration of social media users.

“Everywhere that people tweet about floods, there are observations that could be used,” Eilander said.

This article is published in collaboration with The Thomson Reuters Foundation. Publication does not imply endorsement of views by the World Economic Forum.

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Author: Megan Rowling is a journalist at The Thomson Reuters Foundation.

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