Tuesday, October 20, 2009
Landslide inventories - what you don't know can hurt you
Fewer than half of U.S. states have full or even partial landslide inventories, and less than 10% have active landslide programs, according to a national survey done by Oregon State Geologist Vicki McConnell. In a talk at the Geological Society of America Annual Meeting in Portland, she found that in 35 states landslides are considered a hazard. “The inventories vary in scope and completeness from paper copies of decades-old mapping to interactive web based maps and GIS databases.” [right, national landslide map by the USGS. Note the incompleteness in Arizona, as an example of how poorly they are identified]
A decade ago, then-California State Geologist Jim Davis did a national survey to find out how many active landslides had occurred during a specific period, how much damage they did, and how many lives were lost. The data were incredibly difficult to find. Almost no one tracked it at the state level. In many areas, the information could be found only be gathering articles from small town newspapers.
The situation is not much better today. The national landslide program that the State Geologists pushed for resulted in a small internal effort in the USGS instead of a broad national cooperative effort.
I was talking with Jeff Keaton, engineering geologist extraordinaire, last night who noted that landslide inventories are crucial for local government regulatory decisions related to hazards, but the need to assess vulnerability and risk require much different information. But without the inventories to start with, it seems like we can’t get to reducing vulnerability and risk.