Periglacial Preconditioning of Debris Flows in the Southern Alps, New Zealand

Sattler, Katrin

doi:10.1007/978-3-319-35074-5

Cited by 8 publications

(5 citation statements)

References 308 publications

(524 reference statements)

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“…No detailed meteorological data are available for the study area. Mean annual air temperatures (MAAT) for active rock glaciers in the Southern Alps have been modelled to be positive and among the highest reported on a global scale (see Sattler, 2016; Sattler et al, 2016, for details). MAAT for Irishman Stream Valley head should be around 0°C or slightly above at 2000 m a.s.l and it has a southerly aspect.…”

Section: Study Areamentioning

confidence: 99%

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Age constraints of rock glaciers in the Southern Alps/New Zealand – Exploring their palaeoclimatic potential

Winkler

2018

The Holocene

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Two rock glaciers in the valley head of Irishman Stream in the central Ben Ohau Range, Southern Alps/New Zealand, have been investigated using the electronic Schmidt-hammer (SilverSchmidt). Longitudinal profiles on both features reveal a consistent trend of decreasing R(Rebound)-values and, hence, increasing weathering intensity and surface-exposure age on their numerous transverse surface ridges from rooting zone towards the front. Previously published numerical ages obtained by terrestrial cosmogenic nuclide dating (TCND) allowed the calculation of a local Schmidt-hammer exposure-age dating (SHD) age-calibration curve by serving as the required fixed points. Age estimates for the lowermost rock glacier surface ridges fall within the early Holocene between 12 and 10.5 ka and indicate a fast disappearance of the Late Glacial glacier formerly occupying the valley head, followed by the initiation of rock glacier formation around or shortly after the onset of the Holocene. Although it cannot be judged whether the rock glaciers investigated were active within the entire Holocene or only repeatedly during multiple episodes within, their location and intact morphology exclude any substantial glacial activity at Irishman Stream during the Holocene. This has considerable regional palaeoclimatic implications because it opens for the hypothesis that climatic conditions during early Holocene were possibly comparatively dry and favourable for rock glacier initiation, but less so for glaciers. It would also challenge the view that air temperature is the sole major climate driver of glacier variability in the Southern Alps. More work utilising the palaeoclimatic potential of rock glaciers in the Southern Alps is advised.

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Section: Study Areamentioning

confidence: 99%

“…But it does not reach the central Ben Ohau Range. Irishman Stream is located east of the 2000 mm isohyet (Sattler, 2016; Tait et al, 2006). It seems too dry to support considerable Holocene glaciation, thus allowing the formation of rock glaciers practically absent in the more westward parts of the Southern Alps.…”

Section: Study Areamentioning

confidence: 99%

Age constraints of rock glaciers in the Southern Alps/New Zealand – Exploring their palaeoclimatic potential

Winkler

2018

The Holocene

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“…Large parts of the cirque are steep enough for debris flow initiation and composed of supply-unlimited loose material (cf. Sattler, 2016). The eastern parts of the cirque are even continuously replenished through gravitational processes with sediments originating from above the first steep rock step (Fig.…”

Section: Potential Ppdf Initiation Zonesmentioning

confidence: 99%

Scenario building and runout modelling for debris flow hazards in pro-/periglacial catchments with scarce past event data: application of a multi-methods approach for the Dar catchment (western Swiss Alps)

Fischer,

Kummert,

Aeschbacher

et al. 2023

Preprint

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Abstract. In high mountain areas, the disposition (susceptibility of occurrence) for debris flows is increasing in steep terrain, as – due to climate change – rapid glacier retreat and permafrost degradation is favouring higher availability of loose sediments. The probability of occurrence and magnitude of pro- and periglacial debris flows is increasing, too, as triggering events such as heavy thunderstorms, long-lasting rainfalls, intense snow melt or rain-on-snow events are likely to occur more often and more intensely in future decades. Hazard assessment for debris flows originating from pro- and periglacial areas is thus crucial but remains challenging, as records of past events on which local magnitude-frequency relationships and debris flow scenarios can be based on are often scarce or inexistent. In this study, we present a multi-methods approach for debris flow hazard scenario building and runout modelling in pro- and periglacial catchments with scarce past event data. Scenario building for the debris flow initiation zone reposes on (i) the definition of meteorological and hydrological triggering scenarios using data on extreme point rainfall and precipitation-runoff modelling, and (ii) the definition of bed load scenarios from empirical approaches and field surveys. Numerical runout modelling and hazard assessment for the resulting debris flow scenarios is carried out using RAMMS-DF, which was calibrated to the studied catchment (Le Dar, western Swiss Alps) based on the area of debris flow deposits from the single major event recorded there in summer 2005. The developed approach is among the first to propose systematic scenario building for pro- and periglacial debris flows triggered by precipitation dependent events.

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“…Active periglacial processes (sub-zero temperature fluctuations) are likely to affect the higher slopes. Rock glaciers have been mapped in the Two Thumb ranges and some in the higher, northern parts of the range are likely still active where permafrost presence is modeled (Sattler, 2016;Sattler et al, 2016). No glaciers presently exist in the central Two Thumb range but there are cirque glaciers (mostly >1900 m asl) and a few small valley glaciers (terminating >1200 m asl) in the northern part of the range, 20-30 kilometers farther north.…”

Section: Study Site and Settingmentioning

confidence: 99%

The Anomalously Old Bush Stream Rock Avalanche and Its Implications for Landslide Inventories in Dynamic Landscapes

McColl

2020

Front. Earth Sci.

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Previous dating of rock slope failures in most glaciated mountain chains has revealed almost exclusively young, mostly Holocene ages. In this study, a rock avalanche in the glaciated Rangitata Basin in Canterbury, New Zealand is mapped, described, and dated, revealing a pre-Holocene age of failure. The geomorphology and characteristics of the rock avalanche, named here as the Bush Stream Rock Avalanche, were assessed from field mapping and photogrammetric analyses. To assess the age of the rock avalanche, in situ cosmogenic 10 Be exposure dating was applied to boulders on the deposit. The geomorphological mapping shows that the morphology of the head scarp and deposit of the rock avalanche are distinct from the surrounding landscape, much of which appears to be glacial in origin. The rock avalanche traveled about 4 km, with a volume of 50-100 M m 3 , and appears to have temporarily blocked Bush Stream. The dated boulders suggest an age of >16 ka (and likely >20 ka), making it the oldest reported alpine rock avalanche in New Zealand, and one of the oldest last-glaciation rock avalanches to be reported worldwide. Deep depressions, possibly kettle holes, in the deposit are indicative of runout over a glacier (or associated dead ice), but any glacier present at the time must have been small and probably decaying. The excellent preservation was likely favored by a small catchment located on the dry lee side of the Two Thumb Range which dampened glacial and fluvial activity. The study confirms that rock avalanches were being produced in the Southern Alps early in the last glaciation or early period of deglaciation, but that evidence for them likely exists only in the rare environments that have conditions favorable for preservation. Preservation potential in most of the Southern Alps is low, with older deposits readily buried or eroded by New Zealand's high rates of erosion, aggradation, and dynamic processes. Unless methods can be developed to identify missing older events, we are hampered in our ability to understand the frequency, and therefore causes, of large slope failures in the Southern Alps and in other highly dynamic alpine landscapes.

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Periglacial Preconditioning of Debris Flows in the Southern Alps, New Zealand

Cited by 8 publications

References 308 publications

Age constraints of rock glaciers in the Southern Alps/New Zealand – Exploring their palaeoclimatic potential

Age constraints of rock glaciers in the Southern Alps/New Zealand – Exploring their palaeoclimatic potential

Scenario building and runout modelling for debris flow hazards in pro-/periglacial catchments with scarce past event data: application of a multi-methods approach for the Dar catchment (western Swiss Alps)

The Anomalously Old Bush Stream Rock Avalanche and Its Implications for Landslide Inventories in Dynamic Landscapes

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