Name: Landslide Trigger Point 1997

Display Field: PTYPE

Type: Feature Layer

Geometry Type: esriGeometryPoint

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.

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Supported Query Formats: JSON, geoJSON, PBF

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Supports Statistics: true

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Extent:

XMin: -1.3669359909187192E7
YMin: 4600666.575586665
XMax: -1.3622652410946948E7
YMax: 4677738.16215476
Spatial Reference: 102100  (3857)  LatestVCSWkid(0)

Drawing Info:

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HasZ: false

HasM: false

Has Attachments: false

HTML Popup Type: esriServerHTMLPopupTypeAsHTMLText

Type ID Field: null

Fields:

• OBJECTID ( type: esriFieldTypeOID, alias: OBJECTID )
• USGS.GEO_LND_SLIDE_PT.AREA ( type: esriFieldTypeDouble, alias: USGS.GEO_LND_SLIDE_PT.AREA )
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Supported Operations:   Query   Query Attachments   Query Analytic   Generate Renderer   Return Updates

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