UCLA

Interferometric synthetic aperture radar (InSAR) technology allows for detailed monitoring of levee and delta subsidence, while polarimetric SAR (PolSAR) can detect levee seepage. The dissertation first reviews the history of microwave remote sensing and its basic principles before focusing on case studies of land subsidence (Chapter 1). Northern California’s Sacramento-San Joaquin Delta has an exemplar earthen levee system that protects the area from flooding. The region supports part of the water supply for 25 million residents and contributes billions to the state’s economy from agriculture. However, historical drainage for farming has caused continued subsidence of Delta islands, and threatens their vulnerable levees. Aging flood infrastructure needs to be closely monitored as metropolitan areas globally face increasing inundation risk from sea level rise. To augment traditional ground survey, InSAR is shown to efficiently quantify elevation change along levees with continuous spatial coverage (Chapter 2). Evidence of settling from historic breaks is investigated using a vertical velocity map and time- series of cumulative displacement from data acquired by the UAVSAR (Uninhabited Aerial Vehicle SAR) L-band instrument, during 2009-2015. Previous field studies lack continuous subsidence maps across islands that display local complexities (Chapter 3). Traditional lidar surveys, land cover, elevation, and soil organic matter datasets are compared to explain small- scale subsidence. Threats to levee infrastructure include seepage, which occurs when water moves below the structure, weakening structural integrity. Seeps can be detected using PolSAR, which is sensitive to changes in dielectric constant and surface roughness. Since wet soil has a much higher dielectric constant than dry soil, seepage is shown to be detectable with a polarimetric ratio. The California Aqueduct in the San Joaquin Valley is chosen as a dry testbed to investigate polarimetric seep signatures, and the procedure is also applied to Twitchell Island in the Delta (Chapter 4). The potential to combine SAR and GIS visualization makes instruments like UAVSAR optimal to study deltas. UAVSAR’s airborne capability can be utilized during disasters to detect structural damage and flood extent (Chapter 5). UAVSAR is also the prototype for the upcoming NASA-ISRO satellite, and detailed monitoring and response will be attainable for flood infrastructure globally.