摘要
The dispersion index (d蟽) of topography is introduced. This index is a geomorphic parameter which characterizes each point of topography with respect to the stability/instability of the steepest descent path (SDP) originating from it. The procedure for calculating d蟽 is based on the assessment of SDP variations as the initial topography is also varied within a given elevation 螖h, while a length scale L defines the maximum extent of the SDP. As a result, d蟽 can be derived for different ranges 螖h and different bandwidths L. Since at each point the gravitational force would direct a surface flow along the SDP, d蟽 appears to have a strong influence on the behavior of gravity-driven mass flows, influencing local topographic widening, spreading or channelization. Considering Mount Etna (Italy) as a test case, we present maps of d蟽 for 螖h = 3 m and L = 1, 2, 4 and 8 km, demonstrating also the relationship between the range 螖h = 3 m and Etnean lava flows. Focusing on the 2001 lava flow, we show that the presented maps of d蟽, besides being a tool for viewing morphologies, have interesting applications for hazard assessment related to lava flows.