After a fire, before a flood: NASA's Landsat directs restoration to at-risk areas

NASA: While the 138,000-acre Silver Fire still smoldered, forest restoration specialists were on the job. They analyzed maps created using Landsat satellite data to determine where the burn destroyed vegetation and exposed soil – and where to focus emergency restoration efforts. "The map looked like a big red blob," said Penny Luehring, the U.S. Forest Service's Burned Area Emergency Response and watershed improvement program leader, based in Albuquerque, N.M.

The "before" image (left) is a false-color Landsat 8 image acquired May 28, 2013. The "during" image was acquired, June 13, 2013, while the New Mexico Silver Fire was still growing. (The white puffs with black shadows in the right image are clouds.)

Red means high-severity fire, she explained – and the red areas were concentrated in a watershed drainage that fed communities west of Las Cruces, N.M. So crews got to work. The Burned Area Emergency Response, or BAER, teams are designed to go in as soon as the flames die down to help protect reservoirs, watersheds and infrastructure from post-fire floods and erosion. And Landsat satellites, built by NASA and operated by the U.S. Geological Survey, help direct the crews to those forest areas needing attention.

As a wildfire starts to die down, fire managers like Luehring can contact the Forest Service's Remote Sensing Applications Center in Salt Lake City to request maps that identify the high, moderate and low severity burns. When that call comes in, remote sensing specialist Carl Albury finds satellite imagery of the burned forest both pre- and post-fire. In Landsat images, he looks at two of the 11 spectral bands – the near-infrared band and a short-wave infrared band.

"The near infrared reflects well from healthy vegetation, and the short-wave infrared bands reflect well from exposed ground," Albury said. "By comparing the normalized ratio of the near- and shortwave-infrared bands in the pre-fire image to the post-fire image, we can estimate the burn severity."

Before and after images of the New Mexico Silver Fire, from NASA