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The NGO flying drones to map flooding

People in Need mapping officer Seng Buntheoun prepares a drone for takeoff in Stung Sen earlier this month.
People in Need mapping officer Seng Buntheoun prepares a drone for takeoff in Stung Sen earlier this month. Alessandro Marazzi Sassoon

The NGO flying drones to map flooding

In a freshly bulldozed lot in Kampong Krabao commune, across the Stung Sen River from Kampong Thom’s provincial capital, a team from the Czech NGO People in Need (PIN) is preparing a small Styrofoam drone for a survey flight. The flight is one of hundreds conducted throughout the country since August, with the aim of reducing preventable deaths from flooding through better mapping and an early warning system.

Sun Thun, a teacher at nearby Treal High School, recalls the last major flood to afflict the province in 2011 as “devastating”.

“Many people lost their houses and fields. The flood also destroyed livestock and killed people while tens of thousands did not have enough food or shelter,” he said, adding that schools were also flooded.

If residents had been informed sooner that a flood was coming, Thun said, it could have made a difference.

“As a citizen of the province, I hope the relevant authorities will be able to inform the people about the natural disaster in time, or beforehand so that they could prepare themselves,” he said. That’s a diagnosis People in Need had also made.

“A lot of flood deaths have been caused by a lack of information,” said PIN mapping officer Seng Buntheoun.

“People didn’t know when the flood is coming and where it will affect . . . [but] by measuring the elevation of the terrain, the changes [to the landscape], we can use the data to adjust the warning level accordingly,” he explained.

To that end, PIN has partnered with the provincial and national committees for disaster management in Kampong Thom as well as Kampong Chhnang, Battambang, Pursat, Kratie, Stung Treng, Siem Reap and Banteay Meanchey provinces to overhaul the way the government anticipates and reacts to floods.

According to data compiled by the National Committee for Disaster Management (NCDM), 47 percent of deaths due to natural disasters are caused by flooding, numbering 1,150 since 1996. Flooding has been responsible for destroying or damaging nearly 34,000 homes in that time, and for countless more evacuations. Just last year in Kampong Thom, flooding damaged some 1,300 houses.

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According to NCDM spokesman Keo Vy, while the province has been spared from major flooding since 2013, it remains one of the most vulnerable regions in the country.

“Kampong Thom, due to its geographical location, is very vulnerable to floods,” he said, noting “water levels have usually risen close to the warning point over the past four years”.

Since 2013, PIN has been scaling up an automated flood warning system over cell phone networks, and last year they began installing sonar-based water level gauges that ping information directly to local authorities, further streamlining the process of notifying residents by phone.

According to Vy, some 70,000 people have registered to use the phone service across 10 provinces.

One such gauge was installed by PIN this month on the Stung Sen Bridge, which could reduce the time it takes for authorities to warn the public from a matter of hours or days to just a few minutes.

Now PIN is flying two $10,000 drones equipped with 18-megapixel cameras to create 3D topographic maps that will for the first time provide authorities with knowledge of how an area will be flooded.

Back on the lot, mapping officer Buntheoun has charted the automated flight path for the day’s survey on a laptop, hooked up to a mobile GPS base. Holding the two-kilogram drone by its wings, he gives it a shake, a propeller begins to whirr, and he launches it into the air like it’s a jumbo paper plane.

“Today we’re mapping about 1.2 square kilometres,” he said. Every few seconds the computer clicks – another photograph received from the camera on the drone’s underbelly.

“The GPS base sends a GPS signal to the drone to give a more precise signal that is accurate to 2 to 3 centimetres,” he explains.

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The Stung Sen Bridge, which was recently outfitted with a gauge to detect water levels and notify residents of flood risks. Alessandro Marazzi Sassoon

That accuracy, he says, is reflected when the photographs are run through a modelling program that transforms them into a 3D map. The result is a far cry from the maps currently used from 2011, which are outdated and imprecise.

“It’s far more detailed than the old data where the length of each pixel was [equal to] 30 metres. Here it’s four centimetres,” Buntheoun said. “It takes into account landscape changes such as building construction . . . Effects are different from how water will react to a rice paddy versus an urban establishment.”

Heng Sarith, a member of the Kampong Thom provincial committee for disaster management said the updated maps will be a “great” help.

“It shows which areas are the most vulnerable to natural disasters, and which areas are the least affected,” he says.

After 20 minutes, the drone flying overhead comes in for a landing, its battery is swapped out and then it is quickly back in the air. Taken from 200 metres above ground, the pictures will be stitched together, creating a mosaic of the area, and of its vulnerabilities.

Residents living in flood-prone areas can call 1294 for free to subscribe to the flood alert information system.

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