Feasibility study of differential SAR interferometry for subsidence monitoring in the Sacramento-San Joaquin Delta

Studies the spatial and temporal variability of land subsidence in the Sacramento-San Joaquin Delta region, using interferometric SAR (INSAR) data. Land subsidence in the delta has been the subject of scientific study and political debate. As a result of historical subsidence rates of 1-3 inches/year since the early 1900s, the interiors of many of the delta's islands lie significantly below sea level. Continued subsidence poses a threat to the integrity of the levee system designed to protect the islands from flooding. The goal of the current work is two-fold: first, the technical feasibility of remotely measuring very small elevation changes in predominately agricultural lands is evaluated; second, establishing a mechanism for the integration of remotely sensed information into the decision making process for environmentally sensitive regions. Advances in differential interferometric SAR (DIFSAR) techniques have demonstrated that coherent, repeat pass radar measurements can be processed to detect elevation changes on the order of several cms. ERS 1/2 data have been obtained over the delta at intervals ranging from one day to one year with baselines on the order of 100 m or less. These data have been processed to determine the feasibility of applying the DIFSAR technique to provide critical information to the planning process for this region. Results indicate the expected fall-off in coherence with repeat pass temporal separation for C-band radar.