SAR uncovers critical data on storm damage

Insurance adjusters and forest recovery teams monitor wind impact with radar imagery from space

On the evening of 26th November 2021, not long after Scotland had hosted the UN Climate Change Conference (COP26), storm Arwen brought havoc to Scottish forests, impacting an important economic sector in the country. Blowing in from the northeast, Arwen was Scotland’s most damaging storm in half a century, affecting an estimated 1 million cubic meters of timber – that’s about 20% of the annual harvest. In response, Earth Blox, Capella Space and Edinburgh University have been working together to see if satellite radar can support efforts to map where the damage has occurred. 

For forest owners worldwide, storm damage is second only to fire in terms of risk, based on severity and frequency of occurrence. Catastrophic damage to forests caused by wind is referred to as “windthrow.” When and where windthrow happens is not easy to predict, as it is influenced by many factors, not just the speed of the wind. It is therefore vital to collect information on where windthrow has occurred after an event so that the timber can be salvaged and impacts on the timber market can be mitigated. Typically, not only is there a risk that the quality of the timber degrades, but there is also a risk that recovered wood creates an oversupply on the local market and prices drop. 

To aid recovery and support the management of supply, it is essential to map areas of wind damage as quickly and accurately as possible. Forest owners, sawmills and the insurance companies that support them need this information swiftly. Wind damage is one of the most important insurable risks for planted forests. One key challenge when trying to map windthrow with traditional optical imagery is that it is difficult to tell the difference between wind damage and other changes to the forest, such as standard clear-felling (which may have been occurring right up until the storm). Other subtle variations in the forest may also suggest wind damage when there is none.

Insurance adjusters and disaster recovery teams typically monitor windthrow with drones and helicopters or with boots on the ground. These methods are very expensive and difficult in high winds conditions. They are also limited to daylight hours and can be complicated by challenging terrain. On top of that, optical imagery from drones and helicopters or from satellites in space is also obstructed by cloudcover and limited to daylight hours. With synthetic aperture radar (SAR) technology, these challenges are quickly overcome.

This is why teams at Earth Blox and Edinburgh University tasked the Capella Space SAR satellites to capture highly detailed images of areas across Scotland where Earth Blox had identified sites of likely windthrow. With the capacity to capture imagery in the dark and through clouds, the high-resolution SAR images started to come through for analysis within 24 hours. The high-resolution SAR images from Capella have been used successfully to map other landscape changes, such as damage caused by hurricanes, landslides, volcanic eruptions and wildfires. And as can be seen in the image below, even a quick visual inspection clearly picks out the areas of windthrow, as it looks like the forest has been “combed-over” – this is where the individual tree trunks are being picked up by Capella’s SAR. In these images, there is little ambiguity as to what is windthrow and what is not. 

With the rapid and large geographic coverage afforded by the Earth Blox tool, combined with the precision imaging from Capella SAR satellites, it is now feasible for forest owners and insurance companies to generate quick and accurate assessments of post-storm damage.

To learn more about how SAR can assess storm damage and forest destruction, contact Capella today.

Watch a demo of catastrophe modeling from Earthblox, a member of the Capella SAR Community.

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