Monitoring of urban subsidence in coastal cities: Case studies Vancouver and Seattle

The advanced processing methodology is presented for extracting information from earth observation data. Using imagery from various Synthetic Aperture Radar (SAR) satellites and Multidimensional Small Baseline Subset Differential Interferometric SAR (MSBAS-DInSAR) processing methodology we observed ground subsidence in Vancouver (British Columbia, Canada) and Seattle (Washington, USA). In Vancouver, subsidence with rate of up to 2 cm/year was detected during 1995–2012 over a broad area, including the Vancouver International Airport. In Seattle, subsidence with rate of up to 3 cm/ year was detected during 2012–2015. Between August 2014 and August 2015, unusually fast subsidence occurred beneath the city center. This subsidence is caused mainly by human activities, such as construction, urban infrastructure development and groundwater extraction, but also by natural processes, such as consolidation of sediments. Located in coastal areas, these cities may become affected by flooding if ground level subsides below the sea level or due to storm surge. The risk of flooding increases as the sea level continues to rise due to the climate change. The advanced image processing methodology of earth observation data described here allows near real-time monitoring of ground subsidence with high spatial resolution and high precision, therefore increasing level of preparedness and mitigating risk.