Map showing inventory and regional susceptibility for Holocene debris flows and related fast moving landslides in the conterminous United States: vector data

Best and Brabb prepared an inventory of past debris flows in 1984 using data from the reconnaissance field investigations and published and unpublished reports, a list of which was eventually published by Alger and Brabb (1985). This information was plotted on 1:500,000-scale USGS state maps and transferred by hand to a 1:2,500,000-scale greenline base map of the United States.

In 1997, this greenline base map was scanned and registered by A. Barron and M. Sinor. The registered map was edited and digitized using ARC/INFO, and the REF database field was completed. No new information was added to the map at that time.

In 1998 and 1999, new information was added to bring the map up-to-date. The data were gathered from published and unpublished reports of debris flows primarily covering the years 1984 -1999. A few older reports were included that had been overlooked in the original map. In addition, all state geologists were contacted to find out if they had information on debris flows. Several state geologists and members of their staff provided significant new information.
If a report included a map at a scale larger than that of the compilation (1:2,500,000), the map or a photocopy was scanned. Other reports contained only the names of places where debris flows had occurred, or a map at a scale smaller than 1:2,500,000, or a map with no geographic coordinates. In those cases, the debris flows were located on the appropriate 1:500,000-scale USGS state map or a 1:100,000-scale USGS topographic map and plotted by hand on a Mylar overlay. This overlay was then scanned.
The scanning was done at 400 dpi on either a UMAX color flatbed scanner or a Contex FSC-8000dsp color scanner, depending on the size of the map or tracing. The scanned images were transformed from scanner coordinates to geographic coordinates in ARC/INFO with digital tics placed by hand. The scanned lines and/or points were edited interactively using ALACARTE (Wentworth and Fitzgibbon 1991), and the database fields (Tables 3 and 4) were filled in as appropriate. In addition, a new database field (table 5) was added to store the name of the state under which the report for a feature on the map was referenced.