Central San Francisco Bay bathymetric change: 1855 to 1979

Metadata also available as - [Outline] - [Parseable text] - [XML]

Frequently anticipated questions:

What does this data set describe?

Title: Central San Francisco Bay bathymetric change: 1855 to 1979
Abstract:
This data release provides a series of four bathymetric change grids generated from historical bathymetric surveys collected in central San Francisco Bay, CA from the 1855 to 1979. The National Ocean Service (NOS) and its predecessor, the United States Coast and Geodetic Survey, collected hydrographic surveys in 1855, 1895, 1920, 1947, and 1979. Surface modeling software was used to generate bathymetric DEMs of each of these surveys. The bathymetric DEMs were then adjusted to account for gridding interpolation bias and changes in sea level through time. The adjusted DEMs for consecutive surveys were then differenced to reveal the amount of sediment erosion and deposition and changes from human activities (e.g., dredging, sand mining, and sediment placement) that occurred through time. These bathymetric change grids are provided here in GeoTIFF format with a horizontal resolution of 25 meters and can be used to quantify net sediment volume change and rates of change throughout the bay.
Supplemental_Information:
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in Esri format, this metadata file may include some Esri-specific terminology.
  1. How might this data set be cited?
    Foxgrover, Amy C., Fregoso, Theresa A., and Jaffe, Bruce E., 20241004, Central San Francisco Bay bathymetric change: 1855 to 1979: data release doi:10.5066/P13H35QB, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    This is part of the following larger work.

    Foxgrover, Amy C., Fregoso, Theresa A., and Jaffe, Bruce E., 2024, Historical bathymetry and bathymetric change within San Francisco Bay, California: 1855 to 2005: data release doi:10.5066/P13H35QB, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Other_Citation_Details:
    Suggested Citation: Foxgrover, A.C., Fregoso, T.A., and Jaffe, B.E., 2024, Historical bathymetry and bathymetric change within San Francisco Bay, California: 1855 to 2005: U.S. Geological Survey data release, https://doi.org/10.5066/P13H35QB.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.160318
    East_Bounding_Coordinate: -122.546101
    North_Bounding_Coordinate: 38.000784
    South_Bounding_Coordinate: 37.721974
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/66760496d34e3cf50fef28ef?name=CB_chg_map_1855_1895.png&allowOpen=true (PNG)
    Sample map of central Bay bathymetric change from 1855 to 1895.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date:
    Ending_Date: 1979
    Currentness_Reference:
    ground condition at time data were collected
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: GeoTIFF
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Raster data set. It contains the following raster data types:
      • Dimensions, type pixel
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 10
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -123.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 25
      Ordinates (y-coordinates) are specified to the nearest 25
      Planar coordinates are specified in Meter
      The horizontal datum used is D North American 1983.
      The ellipsoid used is GRS_1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: N/A, relative vertical change
      Altitude_Resolution: 0.01
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Attribute values
  7. How does the data set describe geographic features?
    floating point
    GeoTIFF of bathymetric change for the specified time period. Z-value in meters, positive values represent sediment deposition and negative represent sediment erosion. Cells with values of -3.4028231e+38 indicate No Data. (Source: Producer defined)
    Value
    Bathymetric change (m) (Source: Producer defined)
    Range of values
    Minimum:-29.44
    Maximum:26.09
    Units:meters
    Resolution:0.01
    Entity_and_Attribute_Overview:
    GeoTIFF of bathymetric change for the specified time period. Z-value in meters, positive values represent sediment deposition and negative represent sediment erosion. Cells with values of -3.4028231e+38 indicate No Data.
    Entity_and_Attribute_Detail_Citation:
    The entity and attribute information were generated by the individual and/or agency identified as the originator of the data set. Please review the rest of the metadata record for additional details and information.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Amy C. Foxgrover
    • Theresa A. Fregoso
    • Bruce E. Jaffe
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Attn: PCMSC Science Data Coordinator
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

Analysis of historical bathymetric surveys enables us to reconstruct the surface of the bay floor through time and quantify spatial and temporal changes in deposition, erosion, and bathymetry over decadal timescales. These data provide insight on changes to San Francisco Bay in response to natural processes as well as anthropogenic activities and can inform numerous studies and applications such as sediment management practices, restoration projects, regional adaptation plans, contaminant transport research, and sea-level rise studies. These data are intended for science researchers, students, policy makers, and the general public. These data can be used with geographic information systems (GIS) or other software to identify changes in the depth of the bay floor through time. These data are not intended to be used for navigational purposes.

How was the data set created?

  1. From what previous works were the data drawn?
    NOAAbathy (source 1 of 3)
    National Oceanic and Atmospheric Administration (NOAA), 2024, NOAA National Centers for Environmental Information (NCEI) Bathymetric Data Viewer website: NOAA / NESDIS / NCEI / Maps / Seafloor Mapping, online.

    Online Links:

    Type_of_Source_Media: Digital Resources
    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.
    NOSshore (source 2 of 3)
    National Oceanic and Atmospheric Administration (NOAA), 2024, NOAA Shoreline Data Explorer website: NOAA / NOS, online.

    Online Links:

    Type_of_Source_Media: Digital Resources
    Source_Contribution:
    NOS Topographic Sheets (T-sheets) to extract mean high water (MHW) shorelines used as DEM extent boundary.
    SFEIshore (source 3 of 3)
    San Francisco Estuary Institute, 1998, San Francisco Estuary Institute EcoAtlas: SFEI, compact disc.

    Type_of_Source_Media: Digital Resources
    Source_Contribution:
    Historical and modern baylands GIS shapefiles used to supplement shorelines extracted from T-sheets, as needed.
  2. How were the data generated, processed, and modified?
    Date: 2006 (process 1 of 9)
    All processes and methods used for developing the 1855, 1895, 1920, 1947, 1979 bathymetric DEMs are outlined in Fregoso and others (2008); please refer to that for more information beyond the summary in this document Data sources used in this process:
    • Fregoso and others (2008)
    Date: 2006 (process 2 of 9)
    Hydrographic sounding data downloaded for all time periods. Pre-1930s surveys were obtained as images of H-sheets that were geoferenced to NAD83 and the soundings manually digitized. Post-1930 soundings were downloaded in digital format (NOAA, 2024). The study area is covered by a compilation of hydrographic surveys that were generally conducted over the span of a few years. The year displayed with the DEMs provided is the year in which the majority of the study area 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. Data sources used in this process:
    • NOAAbathy
    Data sources produced in this process:
    • soundings and contours
    Date: 2006 (process 3 of 9)
    Shorelines were obtained from T-sheets and assigned a spatially variable elevation value of MHW derived from nearby tide stations, ranging from 1.52 to 2.1 m (Fregoso and others, 2008). The 1979 shoreline was modified based upon EcoAtlas data (San Francisco Estuary Institute, 1998). Data sources used in this process:
    • NOSshore
    • SFEIshore
    Data sources produced in this process:
    • shorelines
    Date: 2006 (process 4 of 9)
    Bathymetric contours were digitized from H-sheets or hand drawn as needed to help define the general morphology of the bay floor and to 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. Data sources used in this process:
    • NOAAbathy
    • NOSshore
    Data sources produced in this process:
    • contours
    Date: 2007 (process 5 of 9)
    For each time period, soundings were combined with bathymetric contours and shoreline shapefiles and interpolated into continuous surface models with horizontal resolution of 25 m using ArcInfo's TopoGrid module (now Topo To Raster, Esri, 2024). 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. Data sources used in this process:
    • NOAAbathy
    • shorelines
    Data sources produced in this process:
    • TopoGrid DEMs
    Date: 2007 (process 6 of 9)
    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 Fregoso and others (2008). Data sources used in this process:
    • TopoGrid DEMs
    Data sources produced in this process:
    • BIAS ADJ DEM
    Date: 2007 (process 7 of 9)
    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 124-year span of the surveys. All surveys were adjusted to the 1983-2001 tidal epoch, by adjusting the 1855 survey by -15.9 cm, the 1895 survey by -17.1 cm, the 1920 by -14.9, the 1947 by -11.3 cm and the 1979 survey by -7.0 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. Data sources used in this process:
    • TopoGrid DEMs
    Data sources produced in this process:
    • MLLW ADJ DEMs
    Date: 2007 (process 8 of 9)
    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. Data sources used in this process:
    • MLLW ADJ DEMs
    Data sources produced in this process:
    • Change DEM
    Date: 14-Nov-2024 (process 9 of 9)
    Minor edits were made to the citation links in this metadata file. No data were changed. (mau@usgs.gov)
  3. What similar or related data should the user be aware of?
    Fregoso, Theresa A., Foxgrover, Amy C., and Jaffe, Bruce E., 2008, Sediment deposition, erosion, and bathymetric change in central San Francisco Bay: 1855-1979.

    Online Links:

    Other_Citation_Details:
    Fregoso, T.A., Foxgrover, A.C., and Jaffe, B.E., 2008, Sediment deposition, erosion, and bathymetric change in central San Francisco Bay: 1855-1979: U.S. Geological Survey Open-File Report 2008–1312, 41 p., https://doi.org/10.3133/ofr20081312.
    International Hydrographic Organization (IHO), 2022, IHO standards for hydrographic surveys (6th ed.).

    Online Links:

    Other_Citation_Details:
    reference on hydrographic survey standards provided for added interest to users of these data
    Environmental Systems Research Institute, Inc (Esri), 2024, Topo to Raster help page.

    Online Links:

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    No formal attribute accuracy tests were conducted.
  2. How accurate are the geographic locations?
    Data are as accurate as source data used. No further tests were conducted, and no claims are made to positional accuracy.
  3. How accurate are the heights or depths?
    Data are as accurate as source data used. No further tests were conducted, and no claims are made to vertical accuracy.
  4. Where are the gaps in the data? What is missing?
    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.
  5. How consistent are the relationships among the observations, including topology?
    No formal logical consistency tests were conducted.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints No access constraints
Use_Constraints USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey as the originator(s) of the dataset and in products derived from these data. This information is not intended for navigation purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO
    US

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? Files (CB_chg_1855_1895_m.zip, CB_chg_1895_1920_m.zip, CB_chg_1920_1947_m.zip, CB_chg_1947_1979_m.zip) contain bathymetric change grids in GeoTIFF format for the time period indicated.
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    These data can be viewed with GIS software such as ArcGIS, QGIS, or Global Mapper.

Who wrote the metadata?

Dates:
Last modified: 14-Nov-2024
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-427-4747 (voice)
pcmsc_data@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/DataReleases/ScienceBase/DR_P13H35QB/CentralBay_BathyChange_metadata.faq.html>
Generated by mp version 2.9.51 on Fri Nov 15 15:39:06 2024