Designed to strengthen urban resilience and enhance risk management practices, HARMONIA has provided substantial benefits for the local governments of the 4 pilot municipalities and their citizens. By improving collaboration and designing applications to meet specific needs, HARMONIA has not only refined risk management strategies but also facilitated the identification of critical issues such as landslides and infrastructure weaknesses.
In this article we decided to share the experience of the Sofia municipality in the HARMONIA project, collecting insights from Doncho Barbalov, former employee at the Sofia Municipality, Kristian Milenov from ASDE Sofia, Stefano Salvi from INGV, and Angelo Rabuffetti from Polimi, four of the consortium partners directly involved in the project.
Innovations in Sofia’s urban monitoring
For over a decade, the Sofia municipality has conducted continuous monitoring of urban changes, leveraging Sentinel data and in-situ information provided by local authorities. This comprehensive monitoring includes tracking land cover, land use, critical infrastructure, and natural reserves, enabling the identification of potential geo hazards and areas at risk. Additionally, Sofia has begun applying ISO 9144 standards for land cover and land use assessment, positioning the city ahead in urban planning and environmental management. Moreover, utilizing simulation models adapted from American FEMA standards, Sofia evaluates risks at the functional zone level.
Despite numerous efforts, Sofia, like many cities worldwide, faces new challenges brought about by climate change. To address unpredictable and volatile weather conditions, the city has joined the HARMONIA project. Using the HARMONIA tools, Sofia aims to find solutions for frequent summer droughts and the increasing occurrence of floods during the spring and summer, while also exploring new and potential risks threatening the city.
Identification of critical infrastructe risks and natural hazards
With the tools developed in the project, ASDE and the municipality of Sofia started to explore and identify sources and causes of the issues in the city. HARMONIA’s tools have identified areas at risk of flooding, resulting in calls for regulatory changes to prevent construction in these vulnerable zones. Nevertheless, a significant HARMONIA’s accomplishments in Sofia has been identifying critical infrastructure problems and natural hazards. Collaboration with INGV has allowed to identify several areas affected by anomalous ground motion in southern Sofia districts, prompting further investigation to ascertain whether the cause is natural or infrastructure related. The identification of such phenomena is crucial for the development of risk prevention plans and highlighted the need for improved surveillance of critical infrastructure and illegal buildings, driving Sofia’s administration to enhance its monitoring systems. Moreover, through ground motion measurements performed by INGV in the framework of the project, the city has uncovered evidence of active landslides, with Politecnico di Milano (Polimi) conducting detailed modeling and providing valuable on-the-ground data.
Ground motion due to shallow soil consolidation from recent highway constructions has also been detected. These highways, built on soft alluvial sediments, have caused the ground to adjust to the new load, resulting in measurable ground movement of a few millimeters per year, decreasing with time. Another area of the city, spanning seven square kilometers, is also experiencing subsidence, the most probable cause being overexploitation of the underground aquifer, through excessive water extraction or due to reduced aquifer recharge following climate change effects.
The two maps show the results of the INGV interferometric analysis of hundreds of images of the European Sentinel 1 satellite. For each coloured pixel in the maps the ground motion velocity in mm/year was measured.
The left image shows ground motion velocities in the vertical direction. Upward motion is positive (dark green-blue colours), downward motion is negative (orange-red colours), light green colours indicate ground stability.
The right image shows ground motion velocities in the East-West direction. Motion towards the East is positive (dark green-blue colours), motion towards the West is negative (orange-red colours), light green colours indicate no horizontal (E-W) ground motions.
Geologic and geotechnical concerns
The task involved conducting a thorough analysis of the formation of landslides due to climate change. This analysis considered the latest techniques in geoanalysis and georeferencing, as well as specific algorithms designed to study the interaction between heavy rains and soil instability. Politecnico di Milano (Polimi) developed a reliable method to assist local authorities in deciding the most appropriate actions to prevent landslides induced by climate change. After conducting a comprehensive review of the characteristics of the five municipalities involved in the project, Polimi identified several issues in Sofia that could be exacerbated by the effects of climate change.
They used digital soil modeling to extract geo-morphological data from the existing Digital Elevation Model (DEM) provided by Sofia Municipality, and considered local-scale geological maps for an initial analysis, with the goal of developing a method that could be applied to more specific datasets in the future. The focus was on creating a tool that could be used without restrictions in any landslide context.
Upon inspecting the site in Sofia, experts from Polimi found that the southern area of the municipal territory has the most suitable morphology for our analysis. This area is characterized by hilly reliefs, the presence of the River Iskar and its tributaries, and an artificial basin (Lake Pancharevo).
Researchers used the Bulgarian National Geologic Risks Catalog to initially identify the sites to be analyzed, and find out that the actual relative equilibrium in the Sofia’s territory could be influenced in moderate to medium increase of geological risk in case of heavy and prolonged rainstorms due to the effects of climate change. Thanks to this study the most risky zones were identified, allowing regulators to issue appropriate precautions if needed.
Key role of integrating local and remote sensing applications
Stefano Salvi from INGV highlighted the necessity of integrating local and remote sensing applications to ensure accurate interpretations and effective outcomes. The IRAP collaborative platform has shown promise in harmonizing data from multiple sources, supporting Sofia in comprehensive risk management. Despite these advancements, Kristian Milenov, from ASDE, emphasizes the need to make these monitoring and management processes mandatory. Sofia’s administration is actively working to incorporate these practices into official programs, ensuring sustained and reliable risk management. The support from key stakeholders as the city council members and the mayor is essential for this transition.
As showed by our findings, HARMONIA’s impact extends beyond identifying geohazards; it can also drive significant changes in local policies and practices. The project revealed the necessity for more stringent regulations to prevent construction in risk-prone areas, emphasizing the need for updated building codes and land-use policies. For instance, buildings situated in areas identified as potential landslides zones need to be reassessed, and new regulations should be enforced to prohibit construction in these vulnerable regions. This proactive approach aims to minimize future risks and enhance the city’s resilience to natural disasters.
Sofia and the other three pilot cities will continue to explore the HARMONIA platform and discover new ways to benefit from it. The success of HARMONIA in Sofia sets a benchmark for other municipalities. The ongoing efforts to enhance regular monitoring, integrate various data sources, and develop a network of sensors for natural disasters demonstrate the city’s commitment to resilience. Through HARMONIA, Sofia and the other municipalities are not only advancing their risk management capabilities but also establishing a model for effective municipal governance and urban resilience. This success story illustrates the potential of European projects in addressing complex urban challenges and establishing consolidated tools, as the IRAP platform, to tackle them.
