Laser detection technology is making it easier to identify landslide hazard areas in Portland, according to Dr. Scott Burns, Professor Emeritus of Geology at Portland State.
The laser detection system, called LiDAR, has helped overcome difficulty detecting where landslides might occur, Scott Burns said.
LiDAR is similar to radar but it employs lasers instead of microwaves. The lasers illuminate their targets and map images based on the reflected light.
According to Ali Ryan, Earth Science information officer at the Oregon Department of Geology and Mineral Industries (DOGAMI), LiDAR has increased the number of known landslides in the Portland metropolitan area tenfold, from about 700 to 7,000.
If a landslide has happened previously in a given location, it’s likely to happen there again, Scott Burns said. Existing landslide areas can be identified by the shape of the land where they have occurred, but in forested areas like Portland’s West Hills it can be difficult to see the ground from above.
“The LiDAR allows us to see the ground in Oregon like never before, which allows us to find where landslides have happened in the past and thus helps us predict where they might occur in the future,” said Bill Burns, Engineering Geologist at DOGAMI and former student of Scott Burns.
“We know more than ever before about what the surface of the earth looks like and where natural hazards have left their mark,” Ryan said.
The last 10 years of landslide science have seen rapid advancement of the field, according to Bill Burns.
As new data comes in from the LiDAR system, it’s added to the online Statewide Landslide Information Database for Oregon. Maps are available online.
DOGAMI has partnered with the city of Portland to make new landslide susceptibility maps, perform landslide risk analysis and work with the city to make progress on landslide risk reduction with the new information. Funding for this effort was provided by a grant from the Federal Emergency Management Agency.
The U.S. Geological Survey estimated in 1985 that the total cost of landslides each year in the U.S. was about $1–2 billion per year which, adjusted for inflation, is roughly $2.2–4.4 billion in 2014 dollars. Scott Burns said much of that cost comes as a result of urban landslides, which destroy homes and infrastructure.
The difficulty of finding landslide insurance, Scott Burns said, is one of the reasons he became interested in urban landslides.
“Normal homeowner insurance doesn’t cover landslides. If your house is hit by a landslide or goes sliding down the hill, you lose everything,” he said.
Providing hazard maps and other landslide data makes it easier for insurance companies to start offering landslide protection, Scott Burns said.
The two main environmental factors contributing to landslides are water and earthquakes.
“Here in the Pacific Northwest we have plenty of rain and occasional earthquakes, making our region a hot spot for landslide activity,” Scott Burns said.
In 1996 heavy rain triggered over 700 landslides in the Portland area, a major event which Scott Burns and his students studied extensively.
They found that 9 percent of the landslides might have been prevented if water had been controlled on the properties where they occurred.
The most important thing someone can do to prevent a landslide in a high risk area is to ensure proper water drainage, Scott Burns said. He added that clearing gutters of debris and removing leaves from storm drains can make a big difference.
Scott Burns has devoted much of his 35-year career to studying landslides, and he was named Outstanding Oregon Scientist for 2014 by the Oregon Academy of Science.
He spoke on the subject of urban landslides in a keynote lecture at the in Turin, Italy, in September. The proceedings of the Congress were published earlier this month.
Dr. Scott Burns’ IAEG 2014 Congress keynote lecture is streaming online at www.iaeg2014.com.
Learn more from Dr. Scott Burns, Ali Ryan, and Bill Burns about landslide science in the following video: