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Exploring the use of synthetic aperture radar for detecting and monitoring potential long-term subsidence in the lower Mississippi River valley
Proceedings of the 2020 Mississippi Water Resources Conference
Year: 2020 Authors: Terracina S., Yarbrough L.D.
The Mississippi River alluvial plain (MRAP) is a geophysical province in North America extending from the bootheel of southeast Missouri south along the Mississippi River to the Gulf of Mexico. This study focuses on the lower Mississippi Valley portion of the MRAP that extends from Memphis, Tennessee to Vicksburg, Mississippi and bordered by the Mississippi River to the west. This subset of the MRAP, commonly known as the Delta, is an extensive, low, flat lying area that covers an area of approximately 7,000 square miles and serves as a vital economic resource to the state and region.
Because the Delta is comprised of low strength alluvium, low relief, abundant surface water and shallow groundwater resources, the region is suspectable to several geohazards including flooding, bank stability issues, regional and local subsidence, expansive soils, etc. The New Madrid Seismic Zone to the north also poses additional risk of seismic induced hazards (e.g. liquefaction). Characterizing potential subsidence is of great interest due to increased flood risk along low laying areas near water bodies and impact on levee elevations.
In this project, we investigate the use of the remote sensing technique, interferometric synthetic aperture radar (InSAR) to detect subsidence. InSAR uses waveform phase information of similarly polarized radar pulses from two different acquisition dates to detect displacement on the order of a few millimeters. Preliminary work resulted in the detection of the surface displacement in test locations in southern Louisiana. Our method of analysis was applied to the Delta using the Sentinel-1 satellite platform. The InSAR method relies on a temporal dataset and the greater the time between analysis images the more time is available for displacement to occur. Our initial results show regional subsidence rates are smaller than the detectable limits using InSAR. Additional range (e.g. continued acquisitions) in the temporal database and use of shorter wavelengths could lead to an improved method of subsidence detection and monitoring in the Delta.