Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.
Source_Information:
Source_Citation:
Citation_Information:
Originator: National Oceanic and Atmospheric Administration (NOAA)
Publication_Date: 2024
Title:
NOAA National Centers for Environmental Information (NCEI) Bathymetric Data Viewer website
Geospatial_Data_Presentation_Form: xyz, tif
Publication_Information:
Publication_Place: online
Publisher: NOAA / NESDIS / NCEI / Maps / Seafloor Mapping
Online_Linkage: https://www.ncei.noaa.gov/maps/bathymetry/
Type_of_Source_Media: Digital Resources
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 1857
Ending_Date: 1985
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: NOAAbathy
Source_Contribution:
NOAA NOS single-beam surveys. 1850s to 1920s surveys available as images of NOS smooth sheets, 1930s to 1980s as digital sounding data.
Source_Information:
Source_Citation:
Citation_Information:
Originator: Amy C. Foxgrover
Originator: Bruce E. Jaffe
Originator: Gerald T. Hovis
Originator: Craig A. Martin
Originator: James R. Hubbard
Originator: Manoj R. Samant
Originator: Steve M. Sullivan
Publication_Date: 2007
Title: 2005 Hydrographic Survey of South San Francisco Bay, California
Geospatial_Data_Presentation_Form: xyz
Publication_Information:
Publication_Place: online
Publisher: US Geological Survey
Online_Linkage: https://pubs.usgs.gov/of/2007/1169/
Type_of_Source_Media: Digital Resources
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20050110
Ending_Date: 20050405
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: 2005bathy
Source_Contribution: 2005 single-beam survey conducted by Sea Surveyor, Inc.
Source_Information:
Source_Citation:
Citation_Information:
Originator: National Oceanic and Atmospheric Administration (NOAA)
Publication_Date: 2024
Title: NOAA Shoreline Data Explorer website
Geospatial_Data_Presentation_Form: Raster Digital Dataset
Publication_Information:
Publication_Place: online
Publisher: NOAA / NOS
Online_Linkage: https://nsde.ngs.noaa.gov/
Type_of_Source_Media: Digital Resources
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 1850
Ending_Date: 1985
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: NOSshore
Source_Contribution:
NOS Topographic Sheets (T-sheets) to extract mean high water (MHW) shorelines used as DEM extent boundary.
Source_Information:
Source_Citation:
Citation_Information:
Originator: San Francisco Estuary Institute
Publication_Date: 1998
Title: San Francisco Estuary Institute EcoAtlas
Geospatial_Data_Presentation_Form: shapefile
Publication_Information:
Publication_Place: compact disc
Publisher: SFEI
Type_of_Source_Media: Digital Resources
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 1850
Ending_Date: 1998
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation: SFEIshore
Source_Contribution:
Historical and modern baylands GIS shapefiles used to supplement shorelines extracted from T-sheets, as needed.
Process_Step:
Process_Description:
All processes and methods used for developing the 1858, 1898, 1931, 1956, 1983 bathymetric DEMs are outlined in Foxgrover and others (2004); please refer to that for more information beyond the general overview summary provided in this document
Process_Date: 2004
Process_Step:
Process_Description:
All processes and methods used for developing the 2005 bathymetric DEM are outlined in Foxgrover and others (2007); Jaffe and Foxgrover (2006); please refer to these for more information beyond the general overview summary provided in this document
Source_Used_Citation_Abbreviation: 2005bathy
Process_Date: 2006
Process_Step:
Process_Description:
Hydrographic sounding data downloaded for all time periods. Pre-1930s surveys were obtained as images of hydrographic sheets (H-sheets) that were then geoferenced to NAD83 and the soundings manually digitized. Post-1930 soundings were downloaded in digital format (NOAA, 2024). The 2005 soundings were downloaded in digital format from Jaffe and Foxgrover (2006). This study area is covered by multiple, smaller hydrographic surveys that were generally conducted over the span of one to three years. The year displayed with the DEMs provided is the year in which the majority of the South Bay was surveyed. However, the compilation of surveys covering the entire study area can span many years and end users are encouraged to view the original H-sheets and descriptive reports provided by NOAA (2024) for additional details.
Source_Used_Citation_Abbreviation: NOAAbathy
Source_Used_Citation_Abbreviation: 2005bathy
Process_Date: 2005
Source_Produced_Citation_Abbreviation: soundings and contours
Process_Step:
Process_Description:
Shorelines were digitized from T-sheets and assigned a spatially variable elevation value of MHW derived from nearby tide stations, ranging from 1.83 m in the north, to 2.8 m in the southernmost extent of the study area (Foxgrover and others, 2004). The 1858 and 2005 shorelines were modified base upon EcoAtlas data (San Francisco Estuary Institute, 1998).
Source_Used_Citation_Abbreviation: NOSshore
Source_Used_Citation_Abbreviation: SFEIshore
Process_Date: 2005
Source_Produced_Citation_Abbreviation: shorelines
Process_Step:
Process_Description:
Bathymetric contours were digitized from H-sheets or hand drawn as needed to help define the general morphology of the bay floor and constrain the gridding algorithm. To ensure realistic nearshore morphology in areas where soundings were not collected within close proximity to the shoreline, an additional contour was added parallel to the shoreline, 20 m within the bay and assigned an approximate elevation of mean tide level (MTL). Supplementary contours were manually added to the 1850's tidal flats where the original sounding values have been omitted from the H-sheets.
Source_Used_Citation_Abbreviation: NOAAbathy
Source_Used_Citation_Abbreviation: 2005bathy
Source_Used_Citation_Abbreviation: NOSshore
Process_Date: 2005
Source_Produced_Citation_Abbreviation: contours
Process_Step:
Process_Description:
For each time period, point soundings were combined with bathymetric contours and shoreline shapefiles and interpolated into continuous surface models using ArcInfo's TopoGrid module (now Topo To Raster, Esri, 2024). The 2005 GeoTIFF has a horizontal resolution of 25 m and all other time periods, a resolution of 50 m. The 2005 data was resampled to 50 m prior to generating bathymetric change grids. Bathymetry in tributary channels less than 3-cells wide were excluded because they could not be accurately modeled at the given resolution. Z-values are in meters relative to the MLLW tidal epoch referenced at the time of survey collection.
Source_Used_Citation_Abbreviation: NOAAbathy
Source_Used_Citation_Abbreviation: 2005bathy
Source_Used_Citation_Abbreviation: shorelines
Process_Date: 2005
Source_Produced_Citation_Abbreviation: TopoGrid DEMs
Process_Step:
Process_Description:
An estimate of grid interpolation bias was estimated for each time period by comparing the value of each individual sounding to the cell value of the bathymetric grid at that specific location. Each bathymetric DEM was then adjusted to correct for interpolation bias by deepening the raster surface by the mean values presented in Table 6 of Foxgrover and others (2004). The 2005 survey has and interpolation bias of 0, so no correction was applied. Note that the grid bias values reported in Foxgrover and others (2004) were only included as part of the uncertainty assessment and those corrections were not incorporated into the volume change calculations in that same report. However, for consistency with other San Francisco Bay subembayments in this data release, grid bias corrections have been applied to the GeoTIFFs provided here.
Source_Used_Citation_Abbreviation: TopoGrid DEMs
Process_Date: 2024
Source_Produced_Citation_Abbreviation: Bias ADJ DEMs
Process_Step:
Process_Description:
Prior to generating bathymetric change DEMs for the 1931 to 1956 and 1956 to 1983 time periods, it was necessary to account for land subsidence that occurred within the southern extent of south San Francisco Bay as a result of excessive groundwater withdrawal from 1934 to 1967. Without correcting for subsidence, our grids of deposition and erosion would erroneously overestimate erosion during these time periods. The degree and spatial extent of subsidence documented in Poland and Ireland (1988) was applied to the 1931 to 1956 and 1956 to 1983 change grids following the methodology presented in Foxgrover and others (2004).
Source_Used_Citation_Abbreviation: TopoGrid DEMs
Process_Date: 2024
Source_Produced_Citation_Abbreviation: Subside ADJ DEMs
Process_Step:
Process_Description:
The last step, prior to generating change grids, was to adjust all of the DEMs to a common vertical datum to account for changing survey datums associated with fluctuations in sea level over the 147-year span of the surveys. All surveys were adjusted to the same tidal epoch as the 2005 survey, the 1983-2001 tidal epoch, by adjusting the 1858 survey by -15.8 cm, the 1898 survey by -5.5 cm, the 1931 by -10.3, the 1956 by -6.7 cm and the 1983 survey by -1.8 cm. A negative adjustment (or a deepening of bathymetry) accounts for an increase in the height of the reference tidal datum over time. Neglecting this adjustment, would make the later survey appear deeper than an identical sounding at the same location from the earlier survey, thereby falsely exaggerating the impression of erosion over time.
Source_Used_Citation_Abbreviation: TopoGrid DEMs
Process_Date: 2024
Source_Produced_Citation_Abbreviation: MLLW ADJ DEMs
Process_Step:
Process_Description:
Grids of sediment deposition and erosion amounts between consecutive time periods were generated by taking the above, adjusted DEMs and subtracting latter DEM from the earlier DEM. Z-values are in meters, and positive values represent sediment deposition and negative, sediment erosion.
Source_Used_Citation_Abbreviation: MLLW ADJ DEMs
Process_Date: 2024
Source_Produced_Citation_Abbreviation: Change DEM
Process_Step:
Process_Description:
Minor edits were made to the citation links in this metadata file. No data were changed. (mau@usgs.gov)
Process_Date: 20241114