This study establishes a relationship between the density of canopy gaps and slope stability by using a
high-resolution digital surface model (DSM) made from images recorded by an unmanned aerial vehicle (UAV) to
semiautomatically estimate canopy gap density. Estimated gap density can be employed to identify potentially unstable slopes. The forested slopes adjacent to Xinzhuang Village in southern Taiwan were used as a case study. The estimated canopy gap density is consistent with that of the field investigation. Where the canopy gap density or slope gradient is low, the slope surface is generally undisturbed. Where canopy gaps are dense, tension cracks and scars are often present,bedrock orientation is more erratic, and gullies are more densely spaced on the slope surface. At the Xinzhuang village,a strongly negative relationship was identified between canopy irregularities detected in the DSM and slope instability.Canopy gap density detected with high-resolution DSM may therefore be a useful reference for preliminary slope hazard
mapping.
Key Words: unmanned aerial vehicle, digital surface model, semiautomatic interpretation, canopy gap, slope stability.