Key role of earth observation data for monitoring and assessing volcanic hazard in resource-limited and conflict-affected settings: the case of DR Congo (Africa)

The Virunga volcanoes, including Nyiragongo and Nyamulagira, pose a continuous threat to approximately 2.5 million inhabitants in the cities of Goma (Democratic Republic of the Congo - DRC) and Gisenyi (Rwanda), as well as to the surrounding settlements situated at their base. The volcanic hazards include lava flows, permanent gases and ash emissions, mudflows, ground deformation and fissuring, in addition to the CO2 and CH4 dissolved in lake Kivu, one of the large African Rift lakes situated between the DRC and Rwanda. These hazards are exacerbated by the vulnerable living conditions of the local populations and the insecurity resulting from armed conflicts that have persisted over the last 3 decades. Furthermore, limited financial and technical resources, together with recurrent armed conflicts, have hindered the efforts of the Goma Volcano Observatory (GVO) - the government institution in charge of monitoring the volcanoes and lake Kivu to develop a reliable early warning system, especially ground-based networks. In 2017, a permanent Supersite was established over the Virunga to enhance geophysical scientific research and geohazards assessment, with the aim to assist emergency managers in making informed decisions during volcanic unrest and improve eruption forecasting. In addition to the freely accessible Earth Observation (EO) data (e.g. ASTER, Landsat, Sentinel), the CEOS (Committee on Earth Observation Satellites) guarantees the access -free of charge- to COSMO-SkyMed, Pleiades and SAOCOM images, and supports the production of hazard, risk and recovery maps through the Copernicus EMS services using EO data. The pool of voluntary scientific collaboration built around the Virunga Supersite supports, on a fair basis, the enhancement of the expertise of local scientists for EO data processing and interpretation to improve volcanic hazard assessment and produce effective risk reduction strategies. Hence, the EO data enabled the generation of lava flow hazard maps and the assessment of transportation network vulnerability in Goma. EO data played a crucial role in the emergency response to the May 2021 Nyiragongo eruption, specifically in mapping and modelling the associated dyke intrusion. Furthermore, maps of daily SO2 and ash dispersion are produced as well as the modelling of hazard forecasting. EO data also supports the routine monitoring of Nyiragongo and Nyamulagira volcanoes, enabling the GVO to estimate the daily rate of gas emissions and ground deformation.  It provides critical oversight of Nyiragongo ongoing effusive activity inside the main crater which potentially holds a permanent lava lake, while monitoring Nyamulagira’s intermittent caldera overflows which could give rise to lava flows that threaten populations living south of the volcano. Overall, the availability of EO data and the collaborative effort to generate EO-based data products are key resources to monitor this high-risk volcanic region, overcoming the lack of ground-based networks, and hence are unique tools to promptly assess volcano hazard.