Lidar and Landslides: How the 3D Elevation Program Helps

By Vicki Lukas and William J. Carswell, Jr., U.S. Geological Survey. Fact Sheet 2016–3094, January 2017.

Figure 1: the Oso, Washington, landslide of March 22, 2014; red arrows trace the flow from the top of the scarp. Photo by Mark Reid, USGS, April 1, 2014; the lidar inset uses 3DEP data collected by the Washington Department of Transportation on March 24, 2014.

Why elevation data matter

A core USGS mission is to reduce the loss of life and damage from landslides. The USGS Landslide Hazards Program assesses hazards, investigates and forecasts landslides, helps in emergencies and does outreach — all of it helped by high-resolution 3D elevation data from lidar (light detection and ranging) and IfSAR (interferometric synthetic aperture radar).

Research asks where and when landslides will happen, and how big, fast and destructive they'll be. Its answers feed tools for hazard assessment and situational awareness around storms, earthquakes, volcanoes, coastal erosion and wildfire burn areas. Decision-makers rely on this before, during and after disasters; a nationwide baseline of good elevation data makes all of it better.

Figure 2: shaded relief from a 2013 lidar survey of the North Fork Stillaguamish River valley. Red hatching: the 2014 Oso slide's deposits; colored areas: older landslides from A (youngest) to D (oldest). USGS, after Haugerud (2014).

How landslide work uses 3D data

The conservative yearly benefit to landslide applications in the U.S. is estimated at $20.2 million. The data:

• feed slope-stability models that find where shallow landslides could turn into fast, deadly debris flows;
• give detailed starting conditions for models of landslide initiation and movement;
• help plan evacuations and staging areas;
• make accurate landslide inventories and deposit maps — in dense forest, 3DEP data found 3 to 200 times as many landslides as other methods (Baum and others, 2014);
• provide a baseline for spotting change, such as sediment moving after a wildfire;
• support new ways to estimate landslide thickness and age.

"Landslide hazard assessment at local and regional scales contributes to mitigation of landslides in developing and densely populated areas by providing information for (1) land development and redevelopment plans and regulations, (2) emergency preparedness plans, and (3) economic analysis..." — Baum and others (2014)

The 3D Elevation Program

3DEP is a national USGS program collecting high-resolution elevation data — point clouds, bare-earth elevation models and more. Its goal: quality level 2 lidar for the conterminous United States, Hawaii and the territories, and IfSAR for Alaska, by the end of 2023.

Why a national program:

• economies of scale, cutting acquisition costs by 25 percent;
• predictable federal investment that lets states, Tribes, territories and local governments plan — and "buy up" to higher quality;
• consistent coverage across project, jurisdiction and watershed boundaries;
• simpler buying, with contracts, specifications and quality assurance in place.

Conservatively, 3DEP could deliver $690 million a year in new benefits, and potentially $13 billion a year across the economy (Dewberry, 2012).

Data quality:

Data must be no more than eight years old (Lidar Base Specification).

Products: classified point clouds; bare-earth elevation models with flattened water; seamless national models at 1/3, 1 and 2 arc-seconds; a 1-meter model within each project; and for Alaska, surface models, intensity images and 5-meter elevation models. All are part of The National Map, free and unrestricted (download).

Taking part: partners can fund USGS-managed collection, get cooperative funds to run their own, use USGS contracts and quality control, or contribute data that meet 3DEP standards — mainly through a Broad Agency Announcement. More at the 3DEP website or 3DEP@usgs.gov.

Sources

Based on The 3D Elevation Program—Landslide Recognition, Hazard Assessment, and Mitigation Support, by Vicki Lukas and William J. Carswell, Jr., USGS Fact Sheet 2016–3094, U.S. Geological Survey; a work of the United States government in the public domain. Both figures are taken from the fact sheet's PDF, which the import had left out.