San Francisco Bay Region landslide folio part E - Map of debris-flow source areas in the San Francisco Bay region, California

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

Frequently anticipated questions:

What does this data set describe?

Title:
San Francisco Bay Region landslide folio part E - Map of debris-flow source areas in the San Francisco Bay region, California
Abstract:
This map identifies the principal areas in the San Francisco Bay region that are likely to produce debris flows, which are also called "mudslides." Debris flows that occur in the bay region are fast-moving downslope flows of mud that may include rocks, vegetation, and other debris. These flows begin during intense rainfall as shallow landslides on steep slopes. The rapid movement and sudden arrival of debris flows pose a hazard to life and property during and immediately following the triggering rainfall. Debris flows in a given storm originate from a number of sources scattered throughout steep parts of the landscape, as shown in figure 1 (on map sheet; files sfbr- df.ps, al-df.ps, etc.). During subsequent storms, new debris flows originate from different sources. These various sources, however, are similar in topographic form because debris-flow initiation requires steep slopes and prefers concave parts of hillsides.
  1. How might this data set be cited?
    Ellen, S.D., Mark, R.K., Wieczorek, G.F., Wentworth, C.M., Ramsey, D.W., and May, T.E., 1997, San Francisco Bay Region landslide folio part E - Map of debris-flow source areas in the San Francisco Bay region, California: U.S. Geological Survey Open-File Report 97-0745-E.

    Online Links:

    Other_Citation_Details:
    ARC/INFO vector COVERAGE format (less than 1MB for entire region) and raster GRID format (4.3MB). Plotfiles in PostScript also available.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -123.678
    East_Bounding_Coordinate: -120.975
    North_Bounding_Coordinate: 38.888
    South_Bounding_Coordinate: 36.85
  3. What does it look like?
    http://pubs.usgs.gov/of/1997/of97-745/view.html (PDF)
    PDF representation of debris-flow map sorted by county
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 1997
    Currentness_Reference:
    publication date
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: map
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a vector data set. It contains the following vector data types (SDTS terminology):
      • Entity Point
      • Complete Chain
    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: 500000
      False_Northing: 0
      Planar coordinates are encoded using coordinate pair
      Planar coordinates are specified in meters
      The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.
      The flattening of the ellipsoid used is 1/294.98.
  7. How does the data set describe geographic features?
    SFBR-DFS.PAT
    Mapped 1982 debris-flow sources (contains unique attribute identifications, but none are clear or explained in pamphlet. (Source: OFR-97-0745-E)
    SFBR-DMFL.AAT
    Boundary of mapping of 1982 sources (Source: OFR-97-0745-E)

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • S.D. Ellen
    • R.K. Mark
    • G.F. Wieczorek
    • C.M. Wentworth
    • D.W. Ramsey
    • T.E. May
  2. Who also contributed to the data set?
    The predicted debris-flow source areas were determined by Ellen and Mark by analysis of detailed mapping (Wentworth, 1986; Ellen, Cannon, and Reneau, 1988) that was meticulously digitized by Ramsey and May. The mapped debris-flow sources triggered by the 1982 storm were digitized by Wieczorek and Mark from mapping documented in Ellen and Wieczorek (1988); the boundary of this mapping was digitized by Beukelman. The shaded-relief topographic base was created by Graham using relations provided by R.A. Haugerud.
  3. To whom should users address questions about the data?
    Graymer, Russell W
    USGS-GEO-WRG-NGM
    Mail Stop 975, USGS
    345 Middlefield Road
    Menlo Park, CA
    US

    650-329-4988 (voice)
    rgraymer@usgs.gov

Why was the data set created?

These topographic characteristics are used to predict the likely future source areas shown on this map.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 1988 (process 1 of 2)
    The map was produced using a Geographic Information System (GIS) from a 30- meter-square grid of topographic elevations in the region. The grid of elevations, called a digital elevation model (DEM), permits calculation of hillslope steepness and curvature for each 30-m cell. The potential debris-flow sources shown on the map were determined using the values of steepness and curvature defined in table 1. The parameters in table 1 were determined from values of steepness and curvature at mapped sources of historical debris flows in two calibration areas, one near Montara Mountain in San Mateo County (Wentworth, 1986) and one in Marin County (plate 6 of Ellen, Cannon, and Reneau, 1988). Typical plots describing these measures are shown in figure 2. The values in table 1 were selected by eye from four sets of such plots (two different types of geologic materials in each of the two calibration areas), with the aim of including most of the range of values associated with the mapped sources. Specifically, we used the values where the "sources" curves (fig. 2) attained 50 percent of their maximum value and where the "ratio" curves attained about 50 percent of the value at which they reach a crude plateau. In the meticulously mapped calibration areas, the red zones defined by table 1 include 82 percent of the mapped debris-flow sources. In the bay region as a whole, only 53 percent of the black dots of the map lie within the red zones. This low percentage probably results at least in part from inaccurate location of the black dots due to small-scale base maps used for some of the region-wide mapping.
    Date: 31-Jul-2000 (process 2 of 2)
    Creation of original metadata record Person who carried out this activity:
    Jennifer Lenz
    US Geological Survey
    12201 Surise Valley Drive, Mail Stop 918
    Reston, VA
    USA

    703-648-6974 (voice)
    703-648-6560 (FAX)
    pschweitzer@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 locations of many of these mapped sources may be inaccurate because of the sparse (200 ft) topographic contours present in the 1:62,500-scale base maps, which previously had been enlarged from 1:125,000-scale materials.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Substantially complete
  5. How consistent are the relationships among the observations, including topology?
    The map was produced using a Geographic Information System (GIS) from a 30-meter-square grid of topographic elevations in the region. The grid of elevations, called a digital elevation model (DEM), permits calculation of hillslope steepness and curvature for each 30-m cell. The potential debris-flow sources shown on the map were determined using the values of steepness and curvature defined in table 1.
    Table 1 - Hillslope steepness and curvature used to map potential debris-flow source areas [Values as measured on 30-m elevation grids. Plan curvature is curvature of the ground surface in a horizontal plane; it is measured as 1/r, where r is radius of curvature in meters and negative values indicate concave areas such as swales. Hillslope steepness is dominant in determining potential source areas of the map; plan curvature excludes only 6.5 percent of hillslopes 20 degrees and steeper] 
    Hillslope steepness		Plan curvature
20 degrees and greater		+0.01 and less (including all negative
						 values)

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: none
  1. Who distributes the data set? (Distributor 1 of 1)
    USGS Information Services
    Box 25286, Denver Federal Center
    Denver, Colorado
    USA

    1-888-ASK-USGS (voice)
    1-303-202-4695 (FAX)
    infoservices@usgs.gov
  2. What's the catalog number I need to order this data set? US Geological Survey Open-File Report 97-0745-E
  3. What legal disclaimers am I supposed to read?
    This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
    This database, identified as "Map Showing Principal Debris-Flow Source Areas in the San Francisco Bay Region, California,"has been approved for release and publication by the Director of the USGS. Although this database 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 for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://geo-nsdi.er.usgs.gov/metadata/open-file/97-745/e/metadata.faq.html>
Generated by mp version 2.9.48 on Tue Jul 03 20:07:04 2018