The Solomon Islands experienced heavy rains and flash floods following Tropical Cyclone Ita earlier this year. Over 50,000 people were affected and dozens killed, according to ReliefWeb. Infrastructure damage was extensive; entire houses were washed away and thousands lost their food gardens.
Disaster responders used a rotary-wing UAV (an “Oktocopter”) to assist with the damage assessment efforts. More specifically, the UAV was used to assess the extent of the flood damage in the most affected area along Mataniko River.
The UAV was also used to map an area proposed for resettlement. In addition, the UAV was flown over a dam to assess potential damage. These flights were pre-programmed and thus autonomous. (Here’s a quick video demo on how to program UAV flights for disaster response). The UAV was flown at 110 meters altitude in order to capture very high-resolution imagery. “The altitude of 110m also allowed for an operation below the traditional air space and ensured a continuous visibility of the UAV from the starting / landing position.”
While responders faced several challenges with the UAV, they nevertheless stated that “The UAV was extremely useful for the required mapping” (PDF). Some of these challenges included the limited availability of batteries, which limited the number of UAV flights. The wind also posed a challenge.
Responders took more than 800 pictures (during one 17 minute flight) over the above area which was proposed for resettlement. About 10% of these images were then stitched together to form the mosaic displayed above. The result below depicts flooded areas along Mataniko River. According to responders, “This image data can be utilized to demonstrate the danger of destruction to people who start to resettle in the Mataniko River Valley. These very high resolution images (~ 3 to 5 cm) show details such as destroyed cars, parts of houses, etc. which demonstrate the force of the high water.” In sum, “The maps together with the images of the river could be utilized to raise awareness not to settle again in these areas.”
Images taken of the dam were used to create the Digital Terrain Model (DTM) below. This enables responders to determine areas where the dam is most likely to overflow due to damage or future floods.
The result of this DTM analysis enables responders to target the placement of rubber mats fixed with sand bags around the damn’s most vulnerable points.
In conclusion, disaster responders write that the use of “UAVs for data acquisition can be highly recommended. The flexibility of an UAV can be of high benefit for mapping purposes, especially in cases where fast data acquisition is desired, e.g. natural hazards. An important advantage of a UAV as platform is that image data recording is performed at low height and not disturbed by cloud cover. In theory a fixed-wing UAV might be more efficient for rapid mapping. However, the DTM applications would not be possible in this resolution with a fixed wing UAV. Notably due to the flexibility for potential starting and landing areas and the handling of the topography characterized by step valleys and obstacles such as power lines between mountain tops within the study area. Especially within the flooded areas a spatially sufficient start and land area for fixed wing UAVs would have been hard to identify.”
- Official UN Policy Brief on Humanitarian UAVs [link]
- Common Misconceptions About Humanitarian UAVs [link]
- Humanitarians in the Sky: Using UAVs for Disaster Response [link]
- Crisis Map of UAV Videos for Disaster Response [link]
- Humanitarian UAV Missions During Balkan Floods [link]
- UAVs, Community Mapping & Disaster Risk Reduction in Haiti [link]