LiDAR a Key Component of Landslide Loss Prevention
On Jan. 9, 2018, Americans woke up to the news that mudflows had hit the small seaside town of Montecito, Calif., just south of Santa Barbara. Within just a five-minute period beginning at 3:30 a.m., extremely high intensity rainfalls bore down on this community, creating a debris flow of mud, tree branches, and boulders that were 15 feet in height. Nearly 200 million gallons of rainfall accumulated during the first 15 minutes of the storm. In a matter of minutes, 21 people were killed and two more people went missing and are presumed dead. More than 161 people were injured, 100 homes were destroyed, and the 101 freeway – the major artery connecting Santa Barbara to Los Angeles and closer communities where many workers lived – was shut down for almost three weeks. In addition to the tragic loss of life, there was an enormous economic burden to businesses and workers alike with residential property damage in excess of $200 million, lost wages for local workers estimated at $25-30 million, and more than $7 million spent by Santa Barbara County for emergency response.
Just four years earlier, Oso, Wash., was hit by another devastating landslide that left 43 people dead and caused millions of dollars in damage. In the United States alone, landslide hazards kill 25 to 50 people each year and cause $1.6 billion to $3.2 billion in damages, according to the USGS publication Landslide Hazards – A National Threat.
Landslides are “often more damaging and deadly than the triggering event” according to the USGS. That’s certainly the case for the deadly Montecito mudslide that was preceded by the lengthy Thompson fire. Other examples include the 1964 Alaska earthquake that triggered landslides and the 1980 Mount St. Helens volcanic debris flow. In Rong-Gong Lin II’s recent article for the Los Angeles Times “The ‘nightmare’ California flood more dangerous than a huge earthquake,” he writes about a possible “flood event so grave it would overwhelm our flood-control systems, force 1.5 million people to evacuate, and cause economic damage that could total $725 billion.” This scenario, according to Dale Cox, project manager for the USGS’s Science Application for Risk Reduction, would “dwarf” the financial damage that a 7.8 earthquake would cause.
In the United States, landslides are not restricted to the Pacific Coast. They have wreaked damage across all the United States, including Puerto Rico and the U.S. Virgin Islands. While landslides can strike without warning, there are actions we can take today to help prevent the loss of lives and property including:
- Ensure infrastructure can handle potential flood risks. States and local agencies should ensure they are meeting current federal standards for flood risks. According to the Los Angeles Times article on California floods, “In California, state and local agencies spend $30 million a year to maintain 1,600 miles of levees in the Central Valley; they should be spending $130 million annually to meet current federal standards.” In addition, states, agencies and cities need to assess their aging levees and reservoirs, as well as make sure their flood-control reservoirs are free of debris and ready to handle any downpours.
- Integrate LiDAR slide analysis into prevention efforts. One of the first actions that cities, counties and states can take today is to integrate airborne LiDAR as a vital component in any prevention efforts. Data collected by LiDAR surveys delivers valuable insights into numerous geophysical risks, including the identification of areas that could be prone to landslides. LiDAR’s strengths lie in the fact that it enables you to see through trees and other vegetation to reveal details such as slope, deformation and erosion – features that imagery alone is not capable of showing.
In 2014, just after the Oso landslide, the pre- and post- data collections highlighted how high-resolution LiDAR models can reveal subtle surface features that are undetectable via aerial photographs or field observation. While LiDAR is valuable in landslide assessment and monitoring, it also can be used to proactively identify areas at risk to landslides in the future. By pinpointing areas of concern, officials could undertake mitigation planning and landscape modeling efforts that would ultimately protect people and critical infrastructure. Many geologists have been pushing for better maps that identify landslide-prone areas. And, in response, officials, including those in King County, Wash., and others in Oregon, have begun updating their landslide hazard analysis maps, using LiDAR technology to establish baseline data.
- Support NASA efforts to create the largest landslide database. NASA scientist Dalia Kirschbaum, along with some of her colleagues at the agency, recently launched a Landslide Reporter portal for any member of the public to use “to report the time, location and date of the landslide—as well as your source of information.” It encourages individuals to submit additional details, such as the size of the landslide, what triggered it, and upload. Kirschbaum’s team will be reviewing each entry and then submitting credible reports to the Cooperative Open Online Landslide Repository — which they hope will eventually be the largest global online landslide catalog available.
The ultimate goal is to improve the Landslide Hazard Assessment for Situational Awareness model – essentially a landslide prediction model. While landslides are often triggered by events such as heavy rainfall or rapid snow melt, the likelihood of landslide occurrence is largely described by morphological features such as slope, slope roughness, terrain roughness, stream power metrics, and that distribution of past landslides that are easy to detect and delineate from high resolution elevation models. Landslide susceptibility is exacerbated by factors such as human alternation (roads, slope, land-cover change) and/or natural disturbances, such as wildfires, that are also relatively easy to quantify from LiDAR-derived data sets. LiDAR’s ability to map topography and other factors characteristic of landslides vastly improves hazard assessment and provides extremely valuable input to publicly available landslide databases.
- Pass the National Landslide Preparedness Act. Most importantly, we need to get behind the National Landslide Preparedness Act, which was announced last year by Sen. Maria Cantwell (D-Wash.), Sen. Lisa Murkowski (R-Alaska), Rep. Suzan DelBene (D-Wash.), Sen. Patty Murray (D-Wash.) and Sen. Diane Feinstein (D-Calif.). One of the chief goals of the legislation is to “establish a National Landslide Hazards Reduction Program through the USGS to better identify and understand landslide risks, protect communities, save lives and property and help improve emergency preparedness. In addition, the bill would also direct the USGS to implement a 3D Elevation Program to update and coordinate the collection of elevation data across the country, using enhanced, high-resolution data.” The act was successfully reported out of the House Committee on Natural Resources last December and was sent to the House Science Committee for approval. We strongly encourage Congress to prioritize this legislation.
We have the knowledge and the technology available today to prevent further loss of lives and property to landslides. We just need to act.