From satellite interferometry displacements to potential damage maps: A tool for risk reduction and urban planning

Abstract

Persistent Scatterer Interferometry (PSI) is a consolidated tool for detecting and monitoring ground surface displacements. The availability of satellite data with free access policy and high monitoring capabilities (in terms of resolution and acquisition frequency) is increasing. Moreover, the first continental displacement map of Europe will be freely available in quarter one 2022 by the latest Copernicus Service, the European Ground Motion Service (EGMS). The EGMS will provide ground displacement maps, updated every year, delivering valuable information to a wide range of users, such as public or governmental institutions, industry, academia, and citizens. This vast amount of information needs semi-automatic tools and methodologies to derive user-oriented products that can be easily used by land use and urban planning decision-makers, who are often unfamiliar with PSI. This work proposes a semi-automatic procedure to identify damage prone areas in urban environments from wide-area PSI displacement maps. The proposed method identifies the most significant Active Deformation Areas (ADAs) to calculate three products based on the displacement intensity gradient: the Gradient Intensity Map, the Gradient Vectors and Time Series, and the Potential Damage Map. These products allow identifying buildings and urban structures exposed to potential damage, which could be followed by a more detailed building-based vulnerability and risk assessment. The methodology has been applied to an area of the province of Granada (Andalucía, Spain) but it can be applied to any other urban environment where PSI displacement maps are available. To demonstrate the advantages and limitations of the proposed method, results are discussed in five coastal resorts (Cerro Gordo, Punta de la Mona, Marina del Este, Alfa Mar, and Monte de los Almendros), strongly affected by slope movements. The methodology allowed to derive 175 ADAs from about 200,000 measurement points. About 15% of the resulting area has been found to correspond to high or very high gradient intensity class, and 192 out of 633 buildings have been identified to be prone to moderate or high potential damage. A damage prediction test has been realized through Receiver Operating Characteristic (ROC) analysis, based on a damage inventory map derived from field surveys. The results demonstrate the effectiveness of the methodology to localize damaged or potentially damaged buildings, substantially reducing the time of analysis.