HydroFocus Inc.

Davis, CA, United States

HydroFocus Inc.

Davis, CA, United States
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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.


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.


Hatala J.A.,University of California at Berkeley | Detto M.,University of California at Berkeley | Detto M.,Smithsonian Tropical Research Institute | Sonnentag O.,University of California at Berkeley | And 4 more authors.
Agriculture, Ecosystems and Environment | Year: 2012

The Sacramento-San Joaquin Delta in California was drained and converted to agriculture more than a century ago, and since then has experienced extreme rates of soil subsidence from peat oxidation. To reverse subsidence and capture carbon there is increasing interest in converting drained agricultural land-use types to flooded conditions. Rice agriculture is proposed as a flooded land-use type with CO 2 sequestration potential for this region. We conducted two years of simultaneous eddy covariance measurements at a conventional drained and grazed degraded peatland and a newly converted rice paddy to evaluate the impact of drained to flooded land-use change on CO 2, CH 4, and evaporation fluxes.We found that the grazed degraded peatland emitted 175-299g-Cm -2yr -1 as CO 2 and 3.3g-Cm -2yr -1 as CH 4, while the rice paddy sequestered 84-283g-Cm -2yr -1 of CO 2 from the atmosphere and released 2.5-6.6g-Cm -2yr -1 as CH 4. The rice paddy evaporated 45-95% more water than the grazed degraded peatland. Annual photosynthesis was similar between sites, but flooding at the rice paddy inhibited ecosystem respiration, making it a net CO 2 sink. The rice paddy had reduced rates of soil subsidence due to oxidation compared with the drained peatland, but did not completely reverse subsidence. © 2012 Elsevier B.V.


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.


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).


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.


Deverel S.J.,Hydrofocus Inc | Lucero C.E.,Hydrofocus Inc | Bachand S.,Tetratech Inc
San Francisco Estuary and Watershed Science | Year: 2015

We used available data to estimate changes in land use and wet, non-farmable, and marginally farmable (WNMF) areas in the Delta from 1984 to 2012, and developed a conceptual model for processes that affect the changes observed. We analyzed aerial photography, groundwater levels, land-surface elevation data, well and boring logs, and surface water elevations. We used estimates for sea level rise and future subsidence to assess future vulnerability for the development of WNMF areas. The cumulative WNMF area increased linearly about 10-fold, from about 274 hectares (ha) in 1984 to about 2,800 ha in 2012. Moreover, several islands have experienced land use changes associated with reduced ability to drain the land. These have occurred primarily in the western and central Delta where organic soils have thinned; there are thin underlying mud deposits, and drainage ditches have not been maintained. Subsidence is the key process that will contribute to future increased likelihood of WNMF areas by reducing the thickness of organic soils and increasing hydraulic gradients onto the islands. To a lesser extent, sea level rise will also contribute to increased seepage onto islands by increasing groundwater levels in the aquifer under the organic soil and tidal mud, and increasing the hydraulic gradient onto islands from adjacent channels. WNMF develop from increased seepage under levees, which is caused by changing flow paths as organic soil thickness has decreased. This process is exacerbated by thin tidal mud deposits. Based primarily on projected reduced organic soil thickness and land-surface elevations, we delineated an additional area of about 3,450 ha that will be vulnerable to reduced arability and increased wetness by 2050.


Subsidence of organic soils in the Sacramento-San Joaquin Delta threatens sustainability of the California (USA) water supply system and agriculture. Land-surface elevation data were collected to assess present-day subsidence rates and evaluate rice as a land use for subsidence mitigation. To depict Delta-wide present-day rates of subsidence, the previously developed SUBCALC model was refined and calibrated using recent data for CO2 emissions and land-surface elevation changes measured at extensometers. Land-surface elevation change data were evaluated relative to indirect estimates of subsidence and accretion using carbon and nitrogen flux data for rice cultivation. Extensometer and leveling data demonstrate seasonal variations in land-surface elevations associated with groundwater-level fluctuations and inelastic subsidence rates of 0.5–0.8 cm yr–1. Calibration of the SUBCALC model indicated accuracy of ±0.10 cm yr–1 where depth to groundwater, soil organic matter content and temperature are known. Regional estimates of subsidence range from <0.3 to >1.8 cm yr–1. The primary uncertainty is the distribution of soil organic matter content which results in spatial averaging in the mapping of subsidence rates. Analysis of leveling and extensometer data in rice fields resulted in an estimated accretion rate of 0.02–0.8 cm yr–1. These values generally agreed with indirect estimates based on carbon fluxes and nitrogen mineralization, thus preliminarily demonstrating that rice will stop or greatly reduce subsidence. Areas below elevations of –2 m are candidate areas for implementation of mitigation measures such as rice because there is active subsidence occurring at rates greater than 0.4 cm yr–1. © 2016 The Author(s)

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