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?

San Francisco Bay Region Landslide Folio Part E - Map of debris-flow source areas in the San Francisco Bay region, California
These maps show, for emergency service managers in the San Francisco Bay region, the threshold rainfall that may be capable of triggering a level of debris-flow activity likely to threaten public safety. The maps are products of a continuing series of studies that began after a catastrophic storm on January 3-5, 1982 triggered 18,000 debris flows in the San Francisco Bay region, causing 25 deaths and $66 million in property damage. The threshold rainfall values were estimated by re-evaluating a previous empirical analysis of data from the 1982 storm, and other historical rainfall records, that normalized the rainfall intensity data by dividing by the mean annual precipitation (MAP) of the corresponding rain gage. The present analysis also takes into account the rainfall frequency, the mean annual number of days with non-zero rainfall (#RDs), thereby adjusting for the difference in rainfall frequency between windward-facing slopes where rainfall is orographically enhanced and leeward-facing slopes and valleys that lie within rain shadows where precipitation is reduced. The debris-flow threshold maps were created by digitally combining an existing regional map of mean annual precipitation, a newly compiled data set of #RDs from an analysis of long-term (20-40 years) records of daily rainfall for 33 rain gages in the region, and the re-normalized thresholds from the empirical analysis of historical storm data.
  1. How might this data set be cited?
    Wilson, R.C., and Jayko, A.S., 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-F.

    Online Links:

    ARC/INFO vector COVERAGE format (<1MB for entire region) and raster GRID format (21MB). 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? (PDF)
    PDF representation of the map of 6-hour rainfall thresholds (1.1 megabytes)
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 1997
    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
      UTM_Zone_Number: 10
      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
      Abscissae (x-coordinates) are specified to the nearest unknown
      Ordinates (y-coordinates) are specified to the nearest unknown
      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?
    24 hour rainfall threshold value (Source: OFR-97-0745-F)
    Contour of rainfall threshold (Source: OFR-97-0745-F)
    Range of values
    6 hour rainfall threshold value (Source: OFR-97-0745-F)
    Contour of rainfall threshold (Source: OFR-97-0745-F)
    Range of values
    Point coverage showing rain gage locations, station identifier, average number of rainy days, and mean annual precipitation (Source: OFR-97-745-F)
    Feature name (Source: OFR-97-745-F)
    Santa Cruz 
    Ben Lomond 4 
    Black Mnt 2WSW 
    Calaveras Res. 
    Half Moon Bay 
    Hamilton AFB 
    La Honda 
    Los Gatos 
    Los Gatos 4SW 
    Morgan Hill 2E 
    Mt. Diablo Jnct. 
    Mt. Hamilton 
    Muir Woods 
    Oakland AP 
    Petaluma Fire Stn 
    Redwood City 
    SF Mission Dol. 
    San Gregorio 
    San Jose 
    San RAfael Cif-Ctr 
    Up S Leandro Flt 
    Walnut Creek 2ESE 
    Woodside F.S. 
    Mean annual number of rainy days (Source: OFR-97-0745-F)
    Range of values
    Mean Annual Precipitation (Source: OFR-97-745-F)
    Range of values

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • R.C. Wilson
    • A.S. Jayko
  2. Who also contributed to the data set?
    We thank Todd Fitzgibbon for digital review, and Russ Graymer and Scott Graham for cartographic assistance.
  3. To whom should users address questions about the data?
    Jayko, Angela S
    Mail Stop 975, USGS
    345 Middlefield Road
    Menlo Park, CA

    650-329-4926 (voice)

Why was the data set created?

The primary intended use of these maps is to facilitate response planning for debris-flow related emergencies. The maps are intended to be used in conjunction with the debris-flow susceptibility map developed by Ellen and Mark (1997) in this same series.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?

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

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

    1-888-ASK-USGS (voice)
    1-303-202-4695 (FAX)
  2. What's the catalog number I need to order this data set? US Geological Survey Open-File Report 97-0745-F
  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 "Preliminary Maps Showing Rainfall Thresholds for Debris-Flow Activity, 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?

Last modified: 14-Jun-2016
Metadata author:
Peter N Schweitzer
USGS Midwest Area
Collection manager, USGS Geoscience Data Clearinghouse,
Mail Stop 954
12201 Sunrise Valley Dr
Reston, VA

703-648-6533 (voice)
703-648-6252 (FAX)
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <>
Generated by mp version 2.9.48 on Tue Jul 03 20:07:05 2018