In the mountains of North Carolina, landslides are no joke. Triggered by heavy rains, mountainside soils can become saturated and "unstuck." As a result, what starts as a small landslide can quickly escalate into a huge debris flow that uproots trees and dislodges boulders, scouring everything in its path as it quickly flows downhill at speeds up to 30 mph. The cost—in both infrastructure and human lives—can be devastating.