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Summary of Proposal MTH1340

TitleMonitoring levee subsidence in the Sacramento-San Joaquin Delta area using satellite radar interferometry
Investigator Fay, Emily - Stanford University, Geophysics
Team MemberNo team members defined
Summary

Across the United States, an estimated 100,000 miles of levees protect various regions from flood, storm and hurricane damage. Causes of levee failure include erosion, internal piping, slides of either the levee structure or the foundation, and overtopping. Monitoring levee subsidence over time can help identify areas that have a high risk of failure and direct resources accordingly to prevent major failures. Current inspection methods are conducted from the ground by a team of professionals, and are expensive and labor-intensive. Monitoring of levee systems using satellite data could help improve the efficiency of ground inspections and provide information sooner about areas at high risk of failure. Stripmap InSAR data has spatial resolution of ~3m, which is high enough to localize points on levees. With sufficient temporal coverage, levee subsidence could be monitored seasonally as well as over longer periods. Deformation maps could be created for levee systems covering large areas and used to focus inspection efforts on areas showing subsidence. It would be possible to monitor thousands of miles of levees on a monthly interval without increasing the number of ground inspections.

To test this proposed monitoring method, a levee near Maltby, CA along the Sacramento-San Joaquin delta has been selected. This area is covered by 20 Stripmap images with similar geometry, taken between 2007 and 2011. Once the SAR data has been acquired, it will be processed and the interferograms will be generated, using both the standard method (where coherence allows) and the permanent scatterer method. The displacement maps will be studied, and any subsidence trends noted. For context, levee construction and repair history will be considered, and precipitation records may be consulted if seasonal deformation is shown. A second levee location in the Everglades near Coral Springs, FL has also been selected so that the techniques can be applied in a different environment and the results compared.

The goal of this project is to determine whether InSAR can be used to detect levee subsidence, using either standard interferograms or permanent scatterers. Conclusions will include comments on the ideal temporal coverage for effective monitoring, as well as any issues encountered with signal coherence and how this may relate to the environment surrounding the levee system.Findings will be shared publicly.

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