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Jones C.E.,Jet Propulsion Laboratory | Bawden G.,U.S. Geological Survey | Deverel S.,HydroFocus Inc. | Hensley S.,Jet Propulsion Laboratory | Yun S.-H.,Jet Propulsion Laboratory
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

We have studied the utility of high resolution synthetic aperture radar for levee monitoring using UAVSAR data collected over the dikes and levees in California's Sacramento-San Joaquin Delta and the lower Mississippi River. Our study has focused on detecting and tracking changes that are indicative of potential problem spots, namely deformation of the levees, subsidence along the levee toe, and seepage through the levees, making use of polarimetric and interferometric SAR techniques. Here we present some results of those studies, which show that high resolution, low noise SAR imaging could supplement more traditional ground-based monitoring methods by providing early indicators of seepage and deformation. © 2012 SPIE.

Khan M.A.H.,University of California at Berkeley | Rhew R.C.,University of California at Berkeley | Whelan M.E.,University of California at Berkeley | Zhou K.,University of California at Berkeley | Deverel S.J.,HydroFocus Inc.
Atmospheric Environment | Year: 2011

Net fluxes of methyl halides and chloroform were measured from recently converted rice fields on Twitchell Island, California, using field- and laboratory-based incubations. A stable isotope tracer method was used to demonstrate that the net emissions of CH3Cl and CH3Br during the growing season were predominantly the result of large gross production rates, with gross consumption rates being relatively minor. In agreement with prior studies, the production rates for methyl halides differed significantly at different rice plant growth phases. The Twitchell Island rice field, however, had production rates of CH3Cl during the growth phases that were higher than rates reported at commercial rice fields, presumably because of higher soil chloride concentrations. Laboratory soil incubations showed that the non-flooded rice field soils acted as a small net sink for CH3Cl and as small net sources for CH3Br, CH3I and CHCl3. Despite the higher CH3Cl emissions during the growing season, the overall emissions of halomethanes from the conversion of all potential islands in the San Joaquin Delta to rice paddies is predicted to be an insignificant source of halomethanes. © 2010 Elsevier Ltd.

Jones C.,Jet Propulsion Laboratory | Bawden G.,U.S. Geological Survey | Deverel S.,HydroFocus Inc. | Dudas J.,Delta Suisun Marsh Office | Hensley S.,Jet Propulsion Laboratory
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2011

The islands of the Sacramento-San Joaquin Delta have been subject to subsidence since they were first reclaimed from the estuary marshlands starting over 100 years ago, with most of the land currently lying below mean sea level. This area, which is the primary water resource of the state of California, is under constant threat of inundation from levee failure. Since July 2009, we have been imaging the area using the quad-polarimetric UAVSAR L-band radar, with eighteen data sets collected as of April 2011. Here we report results of our polarimetric and differential interferometric analysis of the data for levee deformation and land surface change. © 2011 IEEE.

Sharma P.,Jet Propulsion Laboratory | Jones C.E.,Jet Propulsion Laboratory | Bawden G.W.,NASA | Deverel S.,HydroFocus Inc.
Remote Sensing of Environment | Year: 2016

Sherman Island, the westernmost island in the Sacramento-San Joaquin Delta in California, plays a crucial role in maintaining the water flux between saline ocean water from the San Francisco Bay to its west and the rest of the Delta to its east. Land elevation below mean sea level and continuous subsidence over the past century has made this island a high priority area for investigations of subsidence and restoration in the Delta. This study reports the results of successful application of Interferometric Synthetic Aperture Radar (InSAR) data and technique to measure subsidence in the Delta, which is a coherence-challenged non-urban area. We carried out a time-series interferometric analysis of Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) L-band (23.8 cm) data, collected from July 2009-August 2014, to assess both the spatial and temporal variation of subsidence on Sherman Island. We report both large-scale (island-wide) subsidence trends and small-scale (levee/farm scale) subsidence features in Sherman Island. Assuming the subsidence is linear during the five years of UAVSAR data acquisition, subsidence rates across the island range from 0-5 cm/yr, with an average of 1.3 ± 0.2 cm/yr. We estimate our systematic uncertainty to be 0.3 cm/yr. Overall, the central region in the island has subsided at a faster rate than the rest of the island. We find our results to be consistent with previous measurements of subsidence rates at electric transmission line towers scattered throughout the island. The results of this study provide insights into several factors influencing subsidence, including soil type, water table depth, land use, land elevation and the location and time of levee repairs. Subsidence monitoring on Sherman Island is essential for maintaining a reliable water supply for the state of California and for protecting the Delta ecosystem. © 2016 Elsevier Inc.

Deverel S.J.,HydroFocus Inc. | Ingrum T.,HydroFocus Inc. | Lucero C.,HydroFocus Inc. | Drexler J.Z.,U.S. Geological Survey
San Francisco Estuary and Watershed Science | Year: 2014

There is substantial interest in stopping and reversing the effects of subsidence in the Sacramento-San Joaquin Delta (Delta) where organic soils predominate. Also, the passage of California Assembly Bill 32 in 2006 created the potential to trade credits for carbon sequestered in wetlands on subsided Delta islands. The primary purpose of the work described here was to estimate future vertical accretion and understand processes that affect vertical accretion and carbon sequestration in impounded marshes on subsided Delta islands. Using a cohort-accounting model, we simulated vertical accretion from 4,700 calibrated years before present (BP) at a wetland area located within Franks Tract State Recreation Area (lat 38.059, long -121.611, hereafter, "Franks Wetland")-a small, relatively undisturbed marsh island-and at the Twitchell Island subsidencereversal demonstration project since 1997. We used physical and chemical data collected during the study as well as literature values for model inputs. Model results compared favorably with measured rates of vertical accretion, mass of carbon sequestered, bulk density and organic matter content. © 2014 by the article author(s).

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