Monitoring of Coastal Subsidence by Combining Multiple Sensors

The population of coastal cities is growing rapidly. Estimates of sea level rise indicate that the frequency and damage caused by coastal tidal inundation will increase in the future. Here we present a method of measuring land motion that allows precise estimates of perigean tidal inundation at coastal cities by combining multiple geodetic observations. No single sensor or geodetic technique is capable of providing all the spatiotemporal coverage and information needed to estimate future inundation around the globe. We combine the strengths of optical imagery and digital surface models (DSMs) with differential interferometric synthetic aperture radar (DInSAR), satellite laser altimetry and global navigation satellite system (GNSS) observations in order to provide street level estimates of inundation. ICESat-2 is used to correct vertical offsets in the DSMs and derive mean sea level. Relative vertical land motion is found using DInSAR with improved coherence when using DSMs from optical imagery. GNSS rates provide an absolute correction to the relative vertical land motions from DInSAR. DSMs provide precise elevations and representations of vulnerable infrastructure. We present initial results from Mumbai, India's largest city and financial capital.