Current Subsidence Rate of the Mississippi River Delta Using Satellite and Ground-based Observations

Abstract:

The Mississippi River Delta is the 7th largest river delta on Earth, and is an economically important coastal region for the United States. The Mississippi delta plain has long been recognized as an area experiencing substantial subsidence and land loss due to a combination of natural and human-induced causes. Better knowledge of current subsidence rates and their main causes are important to long-term state and city planning and hazard mitigation, including ongoing restoration and adaptation efforts. We are using sequential satellite SAR (Synthetic Aperture Radar) images to monitor on-land and offshore surface deformation of the delta. The PS-InSAR (Permanent Scatterer Interferometric Synthetic Aperture Radar) technique is used for InSAR time-series processing. Thousands of offshore oil platforms in the Gulf of Mexico provide an opportunity to apply PS-InSAR to measure offshore deformation here. The oil platforms show strong backscatter in the radar intensity images and high coherence in the InSAR time series. They are used as persistent scatterers. Ground-based observations, including tide gauges, GNSS (global navigation satellite system), optical fiber compaction meters and strainmeters are used to provide accurate spot measurements and to validate the InSAR observations. This work can fill in the large data gaps of subsidence observations in the Mississippi River Delta, extending the mapping of subsidence to the offshore portion of the delta, provided that we account for subsidence rate difference between active and inactive platforms. The improved PS-InSAR method and phase unwrapping strategy developed here also have great potential to be used in other applications.