Nearly a quarter of California's fresh water supply flows through the Sacramento-San Joaquin Delta, an area comprised of tidal marshland and reclaimed land in the form of islands surrounded by levees. The Delta is of critical importance to the state's water supply, contains premier agricultural and recreational resources, and functions as a vital, productive estuarine ecosystem. The area is currently the focus of considerable local, state, and federal investments to improve the ability to meet various and increasing demands of the estuary. Land subsidence and levee instability within the Delta pose serious challenges to meeting goals related to ecosystem restoration planning and land, water resource, and flood disaster management. Similar issues face low-lying regions throughout the world, with increasing risk and uncertainty as sea levels rise. We propose to use the UAVSAR L-band SAR repeat pass interferometry capability to monitor subsidence throughout the Delta by scanning the area monthly for 36 months. With UAVSAR, we can monitor the levees and land surface at a resolution scale unattainable with satellite observations. The permanent scatterers InSAR (PSInSAR) processing technique will be used to characterize the levee stability and to resolve long-time-scale terrain subsidence in order to minimize coherence loss from widespread agriculture production. The proposal team consists of members from JPL, Ca. Dept. of Water Resources, the USGS, and Hydrofocus, Inc. The results of the measurements will be incorporated into DWR's water resource management decision-making process, USGS's water resource assessment process, and state-of-the art dynamic models used to model various long-term policy options and climate change scenarios. This work primarily supports decision-making in the water resources application area, with secondary support of disaster management and climate change assessment, all identified as critical areas in the Decadal Survey. In addition, it supports design of the DESDynI mission, which could use PSInSAR to quantify subsidence and levee instability on a continuing basis around the globe.