British researchers have been using mobile phone data to monitor the movement of people in earthquake-stricken Nepal to better distribute aid.
Originally designed to monitor population flows, the Flowminder application developed by a team from the University of Southampton went through an unexpected test when the catastrophic earthquake hit Nepal in April this year.
"We had been planning to conduct a project of this kind in Nepal since 2014 and the Flowminder team was already in Kathmandu setting this up,” said Andy Tatem Flowminder Director and Professor of Geography at Southampton Andy Tatem. “As a result, when the quake struck, we were able to respond rapidly and were well-placed to help.
The system uses anonymised phone data to track the displacement of populations in affected areas. Every time a person uses a mobile it sends information to a receiving tower and gives an approximate location of where they are. When this information is repeated multiple times, over millions of users, a detailed picture can be extracted of population density, movement and how it changes over time in a given area.
"Although we have used mobile phone data before to measure population movements, this is the first time we have used the method in an ongoing 'live' situation,” Tatem said.
“By watching how the population moves on a daily basis, we have been able to help directly with aid efforts and the rebuilding of infrastructures."
The researchers are cooperating with Nepal’s largest mobile phone operator Ncell, analysing data from 12 million mobiles across the country. By comparing information on the movement of these phones after the quake with population distributions and movements before it hit, the team has established trends of where people are moving to and from.
Shortly after the devastating earthquake, the researchers found that an estimated 500,000 people had left Kathmandu Valley in addition to normal patterns of movement.
Most went to the surrounding districts and the Terai areas in the south and southeast of Nepal - something which had previously been completely unknown. On a wider scale, across the country an estimated 1.8 million people left their home district.
Latest analysis shows that of those people who left their homes soon after the disaster, most have now returned, with approximately four to 14 per cent still remaining elsewhere.
"Large population movements occur each time there is a natural disaster and there is often limited information to help understand where affected people move to - making it difficult to plan a response,” said Robin Wilson who led analyses of the phone data. “The use of mobile phone data that we have pioneered has now proved to be invaluable in a real scenario - helping to get support to where it is needed in an effective way."