New Maps Reveal Landslides Using Laser Based Imaging

New technology is helping state geologists create some of the most accurate landslide inventory maps in the world.

(PORTLAND, Ore.) - The Oregon Department of Geology and Mineral Industries (DOGAMI) has released two maps showing historic and pre-historic landslides in the West Bull Mountain area of Washington County and the northwest portion of Oregon City in Clackamas County.

Using a laser based terrain mapping system called lidar (light detection and ranging) DOGAMI geologists are working with local governments across Oregon to create a new generation of landslide inventory maps that are more accurate and comprehensive than any in the past.

Also, the new mapping protocols put in place (Special Paper 42) mean all future landslides maps in Oregon will be consistent and standardized.

"The benefits are obvious," said State Geologist Vicki McConnell. "If we're able to tell communities where landslides have occurred in the past, they can work to lessen or eliminate landslide hazards in the future."

"Landslide inventory maps are really the first step in an overall strategy to mitigate the effects of landslides where people live," said Geologist Bill Burns, co-author of the new maps and the accompanying technical report. "Once we identify existing landslides, we can then create susceptibility maps that show the most likely places for different types of landslides to occur in the future. That includes maps we're working on right now in Clatsop, Marion, Clackamas, Washington and Multnomah counties."

The new publications include: IMS-26, Landslide Inventory Map of the Northwest Quarter of the Oregon City Quadrangle, Clackamas County, Oregon, by William J. Burns and Ian P. Madin, Oregon Department of Geology and Mineral Industries;

IMS-27, Landslide Inventory Map of the Southwest Quarter of the Beaverton Quadrangle, Washington County, Oregon, by William J. Burns and Ian P. Madin, Oregon Department of Geology and Mineral Industries and;

Special Paper 42, Protocol for Inventory Mapping of Landslide Deposits from Light Detection and Ranging (Lidar) Imagery, by William J. Burns and Ian P. Madin, Oregon Department of Geology and Mineral Industries.

On a yearly basis, damage from landslides is the most costly natural hazard in Oregon, with some years exceeding over $100 million in damage statewide. In 2005, DOGAMI began a collaborative landslide research program with the U.S. Geological Survey (USGS) Landslide Hazards Program to comprehensively identify and better understand landslides in Oregon. This new mapping program using lidar data has identified up to 200 times the number of landslides in areas where traditional mapping methods have been used in the past.