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Service Description: <div style='text-align:Left;'><div><div><p><span>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 sfbrdf.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. These topographic characteristics are used to predict the likely future source areas shown on this map.</span></p></div></div></div>

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• Landslide Trigger Point 1997 (0)

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

Copyright Text: 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.

Spatial Reference: 102100  (3857)  LatestVCSWkid(0)


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Spatial Reference: 102100  (3857)  LatestVCSWkid(0)

Full Extent:

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XMax: -1.3622652410946948E7
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Spatial Reference: 102100  (3857)  LatestVCSWkid(0)

Units: esriMeters

Document Info:

Title: Landslide Trigger Point 1997
Author:
Comments: 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 sfbrdf.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. These topographic characteristics are used to predict the likely future source areas shown on this map.
Subject: This report is a digital database package containing both plotfiles and Geographic Information Systems (GIS) databases of maps of potential debris flow sources, as well as locations of historic debris flow sources, in the San Francisco Bay Region. The data are provided for both the entire region and each county within the region, in two formats. The data are provided as ARC/INFO (Environmental Systems Research Institute, Redlands, CA) coverages and grids for use in GIS packages, and as PostScript plotfiles of formatted maps similar to traditional U.S. Geological Survey map products. There is also a pamphlet available describing the databases and plotfiles. To download databases, plotfiles, or pamphlet, please select the appropriate entry below. Note the disclaimers.
Category:
Keywords: Geologic,Landslide,Debris Flow
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