Some key infrastructure in the reclaimed areas of the Manila Bay Freeport Zone is experiencing significant subsidence or downward ground movement

Land reclamation has been on the rise in the Philippines due to growing demands for land driven by economic and social development. Reclamation, which involves converting water bodies into land masses, requires careful monitoring. Due to climate change, sea levels continue to rise, and the physical load on reclaimed areas intensifies with an increase in structures and population size. This combination of sea level rise and land subsidence poses a significant threat to reclaimed areas. Reclaimed areas are particularly vulnerable to flood hazards. Development activities such as construction, industrialization, and population growth further contribute to potential land deformation, making it vital to monitor whether these areas are subsiding or uplifting. Early detection of such phenomena is crucial for retrofitting, building improvements, and preventive measures. Monitoring is crucial, especially since many commercial establishments and key infrastructures are located within them.

Conventional land deformation monitoring relies on precise leveling, a method that requires extensive fieldwork, complex logistics, and significant manpower. While effective at small scales, this approach becomes impractical for large reclaimed areas due to the substantial resources required. To address these limitations, this study utilizes RADAR satellite data to collect measurement data across the entire reclaimed area.

The study focuses on the Manila Bay Freeport Zone, the country’s largest reclamation project and the site of the former largest shopping mall in Asia, SM Mall of Asia, and other key establishments in its vicinity. Using the Persistent Scatter Interferometry (PSI) technique, the study detects points on the ground and measures the distance of each point relative to the satellite over three years. Changes in these distances indicate deformations. PSI allows for measurements without the logistical and physical demands of traditional leveling.

Results show that while the majority of the study area is generally stable, certain key infrastructures are experiencing significant subsidence. Notable areas include Seascape beside Sofitel, SM by the Bay, City of Dreams, and Solaire, all of which show signs of subsidence with visible physical manifestations. Overall, the technique effectively detects localized deformation and subsidence in reclaimed areas without requiring prior knowledge of existing ground movement.

Authors:

A. L. Lomibao (Department of Geodetic Engineering, College of Engineering, University of the Philippines Diliman), G. A. Leal (Department of Geodetic Engineering, College of Engineering, University of the Philippines Diliman), Luis Carlos Mabaquiao (Department of Geodetic Engineering, College of Engineering, University of the Philippines Diliman | Training Center for Applied Geodesy and Photogrammetry, University of the Philippines Diliman) and Rosalie B. Reyes (Department of Geodetic Engineering, College of Engineering, University of the Philippines Diliman | Training Center for Applied Geodesy and Photogrammetry, University of the Philippines Diliman)

Read the full paper: https://isprs-archives.copernicus.org/articles/XLVIII-4-W8-2023/335/2024/