Possible Costs Associated with Investigating and Mitigating Some Geologic Hazards in Rural Parts of San Mateo County, California

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What does this data set describe?

Title:
Possible Costs Associated with Investigating and Mitigating Some Geologic Hazards in Rural Parts of San Mateo County, California
Abstract:
This publication addresses deep-seated landslide susceptibility, debris flow susceptibility, and other geologic hazards in rural parts of western San Mateo County. The report also estimates possible costs of investigating and mitigating the landslide hazards. The study area includes the Half Moon Bay 7.5' quadrangle, the Montara Mountain 7.5' quadrangle, and the Pescadero/Butano Creeks watershed. Hazard maps were derived by integrating slope data and previous geologic, landslide and debris flow mapping. The digital database includes 43 plotfiles for slope maps, Digital Orthophoto Quadrangle maps, Digital Raster Graphic topographic base maps, geologic maps, deep-seated landslide inventory maps, deep-seated landslide susceptibility maps, and debris flow inventory and susceptibility maps. Twelve ARC export files of supporting digital data are included in the database, and other data have been published previously and are available at other USGS websites named in an accompanying pamphlet (of00-127_2. ps, of00-127_2.pdf, of00-127_2.txt).
All data layers are in Universal Transverse Mercator (UTM) projection, zone 10. The scale of the source maps limits the spatial resolution (scale) of the database to 1:24,000.
Supplemental_Information:
An explanatory pamphlet (of00-127_2.ps, of00-127_2.pdf, of00-127_2.txt) accompanies the digital database.
  1. How might this data set be cited?
    Brabb, Earl E., Roberts, Sebastian, Cotton, William R., Kropp, Alan L., Wright, Robert H., Zinn, Erik N., Mills, Suzanne K., Barnes, Jason B., and Marsolek, Joanna E., 2000, Possible Costs Associated with Investigating and Mitigating Some Geologic Hazards in Rural Parts of San Mateo County, California: U.S. Geological Survey Open-File Report 00-127, U.S. Geological Survey, Menlo Park, CA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.55760384
    East_Bounding_Coordinate: -122.12402152
    North_Bounding_Coordinate: 37.62578981
    South_Bounding_Coordinate: 37.19339877
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2000
    Currentness_Reference:
    The date given is the publication date. The information in the report is the most up-to-date available at the time of publication.
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: geologic map
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector and Raster data set. It contains the following vector data types (SDTS terminology):
      • Point
      • String
      • GT-polygon composed of chains
    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
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 0.0
      False_Northing: -500000
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 1.0
      Ordinates (y-coordinates) are specified to the nearest 1.0
      Planar coordinates are specified in METERS
      The horizontal datum used is NAD27.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.4.
      The flattening of the ellipsoid used is 1/294.98.
  7. How does the data set describe geographic features?
    OF00-127_4A.PAT
    Attribute table of OF00-127_4A.PAT. (Source: ARC/INFO)
    PTYPE
    Landslide label
    ValueDefinition
    DDefinite landslide deposit
    PProbable landslide deposit
    UAUnattributed landslide deposit
    ?Questionable landslide deposit
    OF00-127_4A.AAT
    Attribute table of OF00-127_4A. (Source: ARC/INFO)
    LTYPE
    Type of geologic or geographic feature denoted by a line in the database.
    ValueDefinition
    contact, certainlandslide boundary
    map boundarywatershed boundary
    topographic escarpmentlandslide escarpment
    OF00-127_4B.PAT
    Attribute table of OF00-127_4B. (Source: ARC/INFO)
    PTYPE
    refer to the definition of PTYPE listed for OF00-127_4A.PAT, as all PTYPEs in OF00-127_4A.PAT are identical to those in OF00-127_4B.PAT. (Source: author)
    OF00-127_4B.AAT
    Attribute table of OF00-127_4B. (Source: ARC/INFO)
    LTYPE
    refer to LTYPE definitions listed under OF00-127_4A.AAT, as all LTYPEs in OF00-127_4A.AAT are identical to those in OF00-127_4B.AAT. (Source: author)
    OF00-127_4C.PAT
    Attribute table of OF00-127_4C. (Source: ARC/INFO)
    PTYPE
    Landslide label (Source: author)
    ValueDefinition
    QolOld Quaternary landslide deposit
    Qol?Questionable old Quaternary landslide deposit
    QylYoung Quaternary landslide deposit
    Qyl?Questionable young Quaternary landslide deposit
    OF00-127_4C.AAT
    Attribute table of OF00-127_4C. (Source: ARC/INFO)
    LTYPE
    refer to LTYPE definitions listed under OF00-127_4A.AAT, as all LTYPEs in OF00-127_4A.AAT are identical to those in OF00-127_4C.AAT. (Source: author)
    OF00-127_3A.VAT
    Attribute table of OF00-127_3A. (Source: ARC/INFO)
    VALUE
    debris flow susceptibility (Source: author)
    ValueDefinition
    15having a slope >= 15%
    COUNT
    Number of GRID cells of a VALUE (Source: Computed)
    OF00-127_5A.VAT
    Attribute table of OF00-127_5A. (Source: ARC/INFO)
    VALUE
    relative landslide susceptibility
    Range of values
    Minimum:0
    Maximum:7
    COUNT
    Number of GRID cells of a VALUE (Source: Computed)
    Entity_and_Attribute_Overview:
    The databases in this report were compiled in ARC/INFO, a commercial Geographic Information System (Environmental Systems Research Institute, Redlands, California). Almost all the attributes in the attribute tables of the landslide inventory coverages included in the report are set or calculated by ARC/INFO. The exceptions are "coveragename"-ID, LTYPE, and PTYPE. " coveragename"-ID is required by internal policy to be sequential. This ensures the highest compatibility of our databases with other GISs. Therefore "coveragename"-ID is calculated equal to " coveragename"#, which is a unique, sequential integer assigned by ARC/INFO to each data record. LTYPE and PTYPE are author added items to the coverage AAT or PAT that are used to describe the type of line (LTYPE) or landslide area (PTYPE) being recorded. The PTYPEs define the degree of confidence which the author had when identifying the area as a landslide deposit. All coverages include these items in the data structure. Each item has WIDTH 35, OUTPUT 35, TYPE C. For the susceptibility grids, integers stored in the database field VALUE of the VAT correspond to susceptibility values. In the debris flow susceptibility grids, the value '15' designates cells with a slope greater than or equal to 15%, which corresponds to areas susceptible to debris flows. In the landslide susceptibility grids, each cell is assigned a relative susceptibility value of 0 through 7. The slope grids contain slope data stored as continuous floating-point numbers, and thus a VAT is not present for these grids.
    Entity_and_Attribute_Detail_Citation: This report combined with the explanatory pamphlet: of00-127_2.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Brabb, Earl E.
    • Roberts, Sebastian
    • Cotton, William R.
    • Kropp, Alan L.
    • Wright, Robert H.
    • Zinn, Erik N.
    • Mills, Suzanne K.
    • Barnes, Jason B.
    • Marsolek, Joanna E.
  2. Who also contributed to the data set?
    The authors are grateful to Russell Graymer, David Howell, William Lettis, Bruce Clark, John O'Rourke, Betsy Mathieson, Reid Fisher, Roberta Smith, Gerald Weber, Earl Hart, and John Wade who kindly provided excellent comments used to revise various drafts. Suzanne Mills kindly made corrections to the text, figures and database, and made plots of all the maps. Scott Graham helped to revise the Web text.
    Note: Authorship of the geology of this publication resides in the first six names in the author list in the order given. Sebastian Roberts is also the primary digital database author. The last three names, starting with Suzanne K. Mills, are the other digital database authors in the order given.
  3. To whom should users address questions about the data?
    USGS Western Geologic Mapping Team
    Attn: Database coordinator
    345 Middlefield Road, MS 975
    Menlo Park, CA
    USA

Why was the data set created?

These susceptibility maps and the cost assessment data allow landowners in rural western San Mateo County to determine if their property is impacted by deep-seated landslide and debris flow hazards and, if so, how much money might be required to investigate them. The information is also useful for land use planners, local officials and public interest groups. For example, the maps will be useful for purposes such as determining where sediment from landslides might adversely affect fish in the various creeks, or where roads might be closed after heavy rainfall.

How was the data set created?

  1. From what previous works were the data drawn?
    USGS DRGs (source 1 of 9)
    U.S. Geological Survey, 1991, Digital Raster Graphic Topographic Base Map: U.S. Geological Survey, Reston, Virginia.

    Online Links:

    Source_Scale_Denominator: 24000
    Source_Contribution:
    These digital topographic raster graphics (DRGs) are base maps for the study area.
    USGS DEMs (source 2 of 9)
    U.S. Geological Survey, 1998, 10 meter Digital Elevation Model: U.S. Geological Survey, Reston, Virginia.

    Online Links:

    Source_Scale_Denominator: 24000
    Source_Contribution:
    On the geohazard website, a shaded relief base is always used on the debris flow susceptibility map, may or may not be used on the deep-seated landslide susceptibility map, or may be displayed by itself. Shading the hillsides from a sun angle of 315 degrees clockwise from north, and an azimuth of 45 degrees creates an illusion of three-dimensional topography. The shaded relief is derived from a 10 meter USGS Digital Elevation Model (DEM). This is a raster data set with cells 10 meters on a side and an elevation value interpolated from the orthophotos described below. A shaded relief grid can be made from a DEM using the ARC/INFO GRID 'hillshade' command. The shaded relief is combined on the map with the other data layers, such as the pink debris- flow susceptibility map, by using the ARC/INFO 'gridcomposite' command. The slope maps are also derived from USGS 10-meter Digital Elevation Models (DEMs) using the ARC/INFO GRID 'slope' command. For each 10-meter cell, the slope is calculated from an average of the slope in each of 8 cells surrounding the 10-meter cell. This slope is expressed as percent rise.
    USGS DOQs (source 3 of 9)
    U.S. Geological Survey, October 30, 1991, Digital Orthophoto Quadrangle: U.S. Geological Survey, Reston, Virginia.

    Online Links:

    Source_Scale_Denominator: 24000
    Source_Contribution:
    The Pescadero watershed DOQ map includes parts of 11 separate DOQs spanning 6 quadrangles. The Half Moon Bay quadrangle includes 4 DOQs in their entirety. The Montara Mountain quadrangle includes 6 DOQs because it is slightly larger than a standard USGS quadrangle.
    USGS OFR 98-348 (source 4 of 9)
    Brabb, E.E., Graymer, R.W., and Jones, D.L., 1998, Palo Alto 30' x 60' Quadrangle, California: a digital database: U.S. Geological Survey, Menlo Park, California.

    Online Links:

    Source_Scale_Denominator: 62500
    Source_Contribution:
    The geologic map of the Pescadero watershed is from the digital geologic map of the Palo Alto 30' x 60' quadrangle by Brabb and others (1998). This map shows general distribution of bedrock and surficial deposits that can influence the distribution of landslide deposits and affect mitigation costs. The description of the geologic units represented on the geologic map can be found on the unit description sheet accompanying Open-File Report 00-127.
    USGS OFR 98-137 (source 5 of 9)
    Brabb, E.E., Graymer, R.W., and Jones, D.L., 1998, Geology of the onshore part of San Mateo County, California: A digital database: U.S. Geological Survey, Menlo Park, California.

    Online Links:

    Source_Scale_Denominator: 62500
    Source_Contribution:
    The geologic maps of Half Moon Bay and Montara Mountain quadrangles are from the geologic map of San Mateo County by Brabb and others (1998). This map shows general distribution of bedrock and surficial deposits that can influence the distribution of landslide deposits and affect mitigation costs. The description of the geologic units represented on the geologic map can be found on the unit description sheet accompanying Open- File Report 00-127.
    USGS OFR 97-745e (source 6 of 9)
    Ellen, S.D., Mark, R.K., Wieczorek, G.F., Wentworth, C.M., Ramsey, D.W., and May, T.E., 1997, Map showing principal debris-flow source areas in the San Francisco Bay region, California: San Francisco Bay Region Landslide Folio, U.S. Geological Survey, Menlo Park, California.

    Online Links:

    Source_Scale_Denominator: 125000
    Source_Contribution:
    Debris flow points of origin from these maps are incorporated into the debris flow hazard map included in the OF00-127 database.
    USGS MF-344 (source 7 of 9)
    Brabb, E. E., and Pampeyan, E.H., 1972, Preliminary Map of Landslides in San Mateo County, California: U.S. Geological Survey, Menlo Park, California.

    Source_Scale_Denominator: 62500
    Source_Contribution:
    The digital compilation of the landslide inventory for the Pescadero watershed and the Half Moon Bay quadrangle was derived from this map.
    USGS I-2390 (source 8 of 9)
    Pampeyan, E. H., 1994, Geologic map of the Montara Mountain and San Mateo 7.5' quadrangles, San Mateo County, California: U.S. Geological Survey, Menlo Park, California.

    Source_Scale_Denominator: 24000
    Source_Contribution:
    The digital compilation of the landslide inventory for the Montara Mountain quadrangle was derived from this map.
    USGS MF-360 (source 9 of 9)
    Brabb, E. E., Pampeyan, E.H., and Bonilla, M.G., 1972, Landslide Susceptibility in San Mateo County, California: U.S. Geological Survey, Menlo Park, California.

    Source_Scale_Denominator: 62500
    Source_Contribution:
    The deep-seated landslide susceptibility grids were developed in ARC/INFO GRID and are based on this susceptibility matrix developed by Brabb and others (1972).
    The maps are constructed using three source maps: a slope map, a geologic map, and a landslide inventory map (all described above). To develop the 1972 susceptibility map, Brabb and others superimposed the landslide inventory map onto a geologic map and arranged the geologic units by increasing percentage of area that had failed due to landsliding. The units were then given an overall susceptibility ranging from I (low) to VII (high). The highest susceptibility class (L) was assigned to the landslide deposits themselves, because they were believed to be more susceptible to future landsliding than the rock units from which they are derived. The slope map was then superimposed onto the combined geologic map and landslide inventory map to determine the incidence of landsliding in each geologic unit in each slope category. The overall susceptibility rating for the geologic unit was adjusted downward where no landslides had formed on low slopes. The primary differences between the 1972 map and the susceptibility maps provided here are the use of new slope maps and the use of polygons around just the landslide deposits. On the 1972 map, areas between the deposits and the scarps were also included as a landslide polygon. The matrix table used by Brabb and others (1972) for the entire county is the same one used here. Susceptibility numbers are assigned for each 30-meter cell depending on the unit-slope combination defined in the table. Only the three highest hazard zones, including the landslide deposits (L), are used to determine costs on the web site because these zones are the same ones used by San Mateo County (1973) to restrict development.
  2. How were the data generated, processed, and modified?
    Date: 1998 (process 1 of 2)
    Data from the published sources was combined and interpreted using methods described in Brabb and others (1972).
    Date: 04-Aug-2000 (process 2 of 2)
    Creation of original metadata record Person who carried out this activity:
    S. K. Mills
    U.S. Geological Survey
    345 Middlefield Rd., M/S 975
    Menlo Park, CA
    USA

    650-329-4915 (voice)
    skmills@usgs.gov
  3. What similar or related data should the user be aware of?

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

  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
    The position of each data item is derived from the USGS topographic base map, and therefore additional inaccuracies arising from inaccuracies in the base map may also be encountered.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    The report is intended to be a complete analysis of all previous landslides through 1963 at a 1:24,000 scale.
  5. How consistent are the relationships among the observations, including topology?
    Polygon and chain-node topology present

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
Use_Constraints:
Uses of this digital geologic map should not violate the spatial resolution of the data. Although the digital form of the data removes the constraint imposed by the scale of a paper map, the detail and accuracy inherent in map scale are also present in the digital data. The fact that this database was edited for a scale of 1:24,000 means that higher resolution information is not present in the dataset. Plotting at scales larger than 1:24,000 will not yield greater real detail, although it may reveal fine-scale irregularities below the intended resolution of the database. Similarly, where this database is used in combination with other data of higher resolution, the resolution of the combined output will be limited by the lower resolution of these data.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey Information Services
    Box 25248, Denver Federal Center
    Denver, CO
    USA

    1-888-ASK-USGS (voice)
    1-303-202-4693 (FAX)
  2. What's the catalog number I need to order this data set? USGS Open-File Report OF-00-127
  3. What legal disclaimers am I supposed to read?
    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 publication has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 05-Feb-2016
Metadata author:
Peter N Schweitzer
USGS Midwest Area
Collection manager, USGS Geoscience Data Clearinghouse, http://geo-nsdi.er.usgs.gov/
Mail Stop 954
12201 Sunrise Valley Dr
Reston, VA
USA

703-648-6533 (voice)
703-648-6252 (FAX)
pschweitzer@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:
This page is <https://geo-nsdi.er.usgs.gov/metadata/open-file/00-127/metadata.faq.html>
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