Paraglacial response of steep, sediment-mantled slopes to post-‘Little Ice Age’ glacier recession in the central Swiss Alps

Abstract

This research assesses the morphological consequences of recent (post-‘Little Ice Age’) paraglacial reworking of valley-side sediment mantles in the European Alps. It aims to identify the extent and conditioning factors of slope adjustment at sites in the Swiss Alps, model the temporal pattern, and assess the rates of sediment reworking involved. Gully systems have cut into steep, high-level lateral moraines, and debris cones have accumulated downslope. Debris flow is the dominant agent of sediment transfer. Factors controlling the extent of this activity include moraine slope gradient, relief and moisture availability. Gullies appear to have reached their maximum dimensions within ca. 50 yr of deglaciation, after which gully relief is reduced by removal of inter-gully slopes and gully infilling (within 80–140 yr). On the most recently deglaciated terrain, minimum erosion rates average ca. 95 mm yr−1 since gully initiation, greatly exceeding ‘normal’ erosion rates in other environments. Mean annual accumulation of a single debris cone since ice retreat was calculated to be ca. 30 mm yr−1. Implications of these findings are applied to patterns of paraglacial sediment-mantled slope adjustment, conceptualising paraglacial landscape response in terms of a sediment release exhaustion model, and paraglacial landform succession. Copyright © 2005 John Wiley & Sons, Ltd.