Assessing Rockfall Activity in a Mountain Forest – Implications for Hazard Assessment

Abstract

Rockfall represents the most intensely studied geomorphic process in mountainous areas. Nevertheless, very little information exists on how rockfall frequencies and magnitudes vary over time and how hazards and risks posed by rockfall could be reliably assessed. Former studies have mainly focused on short-term observations of contemporary rockfall activity (Luckman 1976, Douglas 1980), rendering it difficult to estimate long-term accretion rates. Long-term estimates of rockfall accumulation rates have, in contrast, been derived from accumulated talus volumes (Rapp 1960), but such rates may neither be representative of the present-day rockfall activities nor of those that prevailed in the past. On slopes composed of siliceous lithologies, lichenometry has repeatedly been used to evaluate the mean age or activity of talus surfaces (André 1997) or to estimate rates of rockfall accretion (Luckman and Fiske 1995).