Comoros: Digital aerial imaging: keeping one step ahead of climate change risks




Comoros is an archipelago situated off the coast of Mozambique in the Indian Ocean. Cyclones and other climate change-related weather events, of growing strength and frequency, are damaging business, government and the social infrastructure and taking a heavy toll on the poorest slum-dwellers.

The government, which has set a target of achieving emerging-market status by 2030, is just beginning to realise that it can only plan harmonious development, in time and space, if it has a clearer picture of future risks.

In late 2018, the country underwent an aerial photography campaign as part of the Global Climate Change Alliance’s (GCCA) Support to the Union of the Comoros for strengthening resilience to climate change project. The campaign produced a set of high-resolution, orthorectified images with digital surface models covering almost all of the country’s land and sea territory. With unprecedented precision (10 cm resolution, compared to almost 10 m), the images provide a more detailed map of the surface, ranging from buildings, roads, paths and other infrastructure to reefs, mangroves, watersheds and other geomorphological features that either offer protection from climate hazards or heighten their impact.

The aerial images have enabled the production of the first-ever consistent dataset for all three islands (Grande Comore, Anjouan and Mohéli) with documented calculations. For instance, mangrove coverage on Grande Comore has been adjusted from 3 ha to 87 ha, while the size of the Mohéli coral reef has been revised downwards from 18 400 ha to 3 917 ha and 25 m of coast disappeared in 15 years.

batimentThe images and data have also been used to produce new maps of housing, critical infrastructure and communication networks, showing vulnerability to different risks such as rising sea levels, flooding and coastal erosion. Housing maps were produced in 23 pilot areas by over 40 multi-sectoral officials who received training in the use of geographic information systems (GIS).




‘These important images will be of great value to Comoros across all key development sectors for the next 25 years,’ says Dr Anwar Maeva, a lecturer in GIS and remote detection who is using the images in his research into flooding in Hambou and Bambao, two heavily exposed areas of Grande Comore.

Rather than having to apply to the custodian institutions for access, the images have voluntarily been published in open-source format. The new risk maps could play a pivotal role in supporting national efforts to plan ahead and improve disaster-risk management.