Rock avalanches and other landslides in the central Southern Alps of New Zealand: a regional study considering possible climate change impacts

Abstract

Slope instabilities in the central Southern Alps, New Zealand, are assessed in relation to their geological and topographic distribution, with emphasis given to the spatial distribution of the most recent failures relative to zones of possible permafrost degradation and glacial recession. Five hundred nine mostly late-Pleistocene-to Holocene-aged landslides have been identified, affecting 2% of the study area. Rock avalanches were distinguished in the dataset, being the dominant failure type from Alpine slopes about and east of the Main Divide of the Alps, while other landslide types occur more frequently at lower elevations and from schist slopes closer to the Alpine Fault. The pre-1950 landslide record is incomplete, but mapped failures have prevailed from slopes facing west-northwest, suggesting a structural control on slope failure distribution. Twenty rock avalanches and large rockfalls are known to have fallen since 1950, predominating from extremely steep east-southeast facing slopes, mostly from the hanging wall of the Main Divide Fault Zone. Nineteen occurred within 300 vertical metres above or below glacial ice; 13 have source areas within 300 vertical metres of the estimated lower permafrost boundary, where degrading permafrost is expected. The prevalence of recent failures occurring from glacier-proximal slopes and from slopes near the lower permafrost limit is demonstrably higher than from other slopes about the Main Divide. Many recent failures have been smaller than those recorded pre-1950, and the influence of warming may be ephemeral and difficult to demonstrate relative to simultaneous effects of weather, erosion, seismicity, and uplift along an active plate margin.

Glacial lake outburst flood risk in Himachal Pradesh, India: an integrative and anticipatory approach considering current and future threats

“…For implementation within HP, we do not distinguish between whether the slope is bedrock or ice-covered, and assume an impact into a lake is possible from any slope [30°(cf. Allen et al 2011;Fischer et al 2012), where the overall slope trajectory is[14°(cf. Noetzli et al 2003;Romstad et al 2009).…”

On the influence of topographic, geological and cryospheric factors on rock avalanches and rockfalls in high-mountain areas

“…Haberli et al, 2004) and for New Zealand (e.g. Allen et al, 2011). Not only large-volume events have been observed, but also many smaller rockfalls have been observed, for example in the European Alps in the very warm summer of 2003 (e.g.…”

“…Making statements about the likely locations and timing of such mass movement processes on bedrock slopes requires an understanding of the processes and factors relevant for local slope instabilities as well as of the spatial and temporal variability of theses factors. The distribution and characteristics of detachment zones, such as are recorded in inventories, can be used as proxy data for analyses of potential predisposing factors for slope failures (Carrara and Pike, 2008;van Westen et al, 2008;Allen et al, 2011). Thus, establishing relationships between present-day slope failures and hypothesised causal factors is one way of improving understanding of conditions under which instabilities develop.…”

“…Baillifard et al, 2003;Ruff and Czurda, 2008;Allen et al, 2011). Comprehensive data compilation and analyses of rockfall and rock avalanche events in the Swiss and European Alps were undertaken by Abele (1974) and Gruner (2004).…”

Controls on Rockfall-Talus Process-Response Systems, Kananaskis, Canadian Rockies

“…Such factors include the presence of steep rock slopes bedrock (related to the structural geology of the mountains as well as glacial sculpting) and the weathering and development of joints leading to processes such as frost cracking (Luckman & Fiske, 1997;Selby, 1982;Matsuoka & Sakai, 1999;Hales & Roering, 2005). Other hillslope processes such as rock slides, debris slides and debris flows have generally been the subject of more investigations (Anderson & Anderson, 2010;Allen, Cox, & Owens, 2011) compared to the relatively low-magnitude, high-frequency process of rockfall that produces talus slopes (Gardner et al, 1983;Hales & Roering, 2005). Most previous studies of rockfall-talus have focused on local events (e.g.…”