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Eye-witness survivors say there was a loud rumbling noise, then, within minutes, an entire community was consumed by a massive landslide, taking 43 lives and burying 49 homes in the process. The devastation and loss that shook the residents of Oso, Washington resonated across the country as people wondered if they too were vulnerable to such a situation.
The aftermath of the tragic events occurring in Oso, Washington and Grand Mesa, Colorado, have thrust landslide risk assessment into the spotlight as government agencies, property owners and utility companies consider potential consequences to public safety and the local economy in the event of terrain failure. While these prominent events captured the attention of national media and the public’s eye, a U.S. Geological Survey publication reports that each year terrain failure is responsible for 25-50 deaths and an estimated $3.5 billion in damages. The effects of landslides are likely to increase as population centers expand, suburban growth continues and people search for that "quiet home in the hills." In response to the need for more robust information, lidar data has emerged as the leading data source to better understand landslide dynamics.
The Difference is the Detail
The real value of lidar is the incredible level of detail of the surface features in a bare-earth elevation model. Datasets derived from 8 points per square meter or more provides unparalleled visualization of the Earth’s surface, and reveal subtle ground features often undetectable by traditional survey methods. The key, beyond the incredible 1-meter raster resolution, is the ability for lidar to penetrate vegetation, which allows for analysis in forested areas while also revealing historic landslides overgrown with ground cover vegetation. High pulse density lidar datasets continue to discover landslide areas unknown to researchers. In 2011, Ian Madin, chief scientist with the Oregon Department of Geology and Mineral Industries (DoGAMI) reported the discovery of a previously undetected fault line along Mount Hood using lidar collected by Quantum Spatial.
Emergency Response
Within 24 hours of the Oso Landslide, Quantum Spatial deployed a crew to capture lidar data of the massive debris field. The lidar survey provided critical information for first responders, revealing with stunning clarity the extent of the disaster. In similar fashion, a Quantum Spatial acquisition team conducted a high-density lidar survey of the Grand Mesa Landslide to provide intelligence for the Colorado Geological Survey and Colorado School of Mines for use in assessment and monitoring, mitigation planning, and landscape modeling. The data was successfully acquired within a week of the slide and terrain products were delivered within 10 days of acquisition. The depth of information that can be gleaned from lidar coupled with the relatively quick processing time is integral to emergency response efforts.
Risk Assessment
Beyond immediate response to disasters, lidar data is a powerful tool for determining landslide risk. Quantum Spatial has developed proprietary methodology to identify landslides in a semi-automated fashion, producing results for large expanses in a short amount of time. Often the analytics reveal landslide sensitive areas previously unknown, unmapped, and unmanaged.
This new wave of information is helping geologists and planners craft development strategies to improve public safety while gaining better understanding about landslide dynamics.
As a tool for landslide risk management, the process operates under the assumption that the detection of landslides and other forms of ground movement are indicators for future events. Evidence of past terrain failures highlight potential areas of weakness likely to reactivate. The goal is to develop maps and information that determine risk based on geomorphology, terrain history and other factors such as soil type, vegetation cover, hydrology, infrastructure, and land management practices. The Quantum Spatial landslide tool generates multiple layers based on different aspects of the topography, which are then combined to make surface feature aberrations "pop." A training area is implemented to interpret expert derived model values, which are then applied across large study areas.
The landslide tool accurately identifies areas of high, medium and low risk terrain failure. Understanding risk levels across topography aid in preventative planning and mitigation efforts. Predicting landslides is similar to assessing flooding events. The answer to a question such as, "When will the next 100 year flood occur?" is unknown, yet the level of flood risk to specific areas can be mapped and modeled. Likewise, landslide analysis can determine areas of concern, reveal new potential risks, and help experts focus resources in the most vulnerable areas. In places of extremely high risk, conducting lidar surveys and performing change detection analysis on a regular basis can monitor subtle topographic deviations such as surface creep. This type of chronological analysis can be particularly beneficial for landslides, faults, upheaves, and stream channel erosion.
The applications of landslide analysis are relevant to multiple disciplines.
Landslides are of paramount concern for infrastructure siting and maintenance. Quantum Spatial is currently working with several utility companies to minimize risk and increase safety by reviewing existing assets for terrain risks, while aiding in siting new projects. With this hazard analysis, local governments can craft zoning regulations to protect the public.
Making this analysis available to the public can also educate landowners as to the risks on their properties and guide future decisions. In addition, forest management and timber harvesting practices directly impact the level of landslide risk. As such, experts and regulators need access to the best information possible to minimize the impact on surrounding environments. Water quality agencies and aquatic species conservation groups are interested in landslide mitigation efforts to protect sensitive basins.
The Call for Lidar
Often tragedy provides windows of opportunity. The national attention garnered from the colossal devastation of recent high profile landslides has elevated the urgency of improving landslide risk assessment techniques. Federal legislators have discussed potential funding sources for landslide mitigation. Because lidar provides substantial benefits to any landslide management program and offers a whole new level of depth and clarity, it is likely to become the indispensable dataset of the future.
Al Klein specializes in digital and social media and has been an analyst at Quantum Spatial for 7 years.
Layne Bennett has been a Project Manager at Quantum Spatial for 6 years and brings 10 years of experience in the geospatial industry.
Joshua Brockway holds a Master’s degree in Geology with an emphasis on Geophysics and Remote Sensing and has been a part of Quantum Spatial for 2 years.
A 5.178Mb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE