Moraine and Valley Wall Collapse due to Rapid Deglaciation in Mount Cook National Park, New Zealand

First approaches towards modelling glacial hazards in the Mount Cook region of New Zealand's Southern Alps

“…Hazard sources used as input to the MSF model were derived on the basis of satellite terrain mapping and slope gradient thresholds, where the main limitations relate to the 25 m resolution of the DEM, and filtering procedures that operate across several pixel values further increasing the minimum size of recognized surface features (Allen et al, 2008b). In addition, the New Zealand 25 m DTM is developed from 1986 aerial photography, and significant topographic changes have occurred within the glacial landscape over recent decades, most evidently surrounding the larger valley glaciers, where ice surfaces have lowered up to 4 m per year (Blair, 1994). Elevation data computed from ASTER stereo imagery or the 90 m resolution shuttle radar topography mission (SRTM) (Schneider et al, 2008), can keep pace with changing environmental conditions, but provide reduced topographic detail and can have severe errors in steep terrain.…”

“…Fundamental research into phenomena such as ice avalanches (Alean, 1985), glacier-related debris flows (Rickenmann, 1999) and flooding (Clague and Evans, 2000;Haeberli, 1983;Maizels and Russel, 1992) has come from Canada, Central Europe and Iceland, where populated villages and transport infrastructure extend into the glacial environment. Understanding of such processes and potential impacts in the Mount Cook region of New Zealand is comparatively limited, despite recognition of 20th century glacial recession (Chinn, 1996), associated destabilisation of surrounding terrain and lake formation (Blair, 1994;Hochstein et al, 1995), and the potential for large magnitude chain reaction events involving mass movements into glacial lakes (McSaveney, 2002). …”

“…Studies have described flood hazard problems from Franz Josef and Fox Glaciers where the sudden release of sub-or en-glacial reservoirs can mobilise large amounts of sediment (Davies et al, 2003;Goodsell et al, 2005). Debris flow activity initiated during storm events is known to potentially endanger infrastructure within the Mount Cook Village (Skermer et al, 2002;Whitehouse, 1982), and the catastrophic downwasting of large valley glaciers is resulting in widespread moraine wall failure and the destruction of backcountry huts and tracks (Blair, 1994). Ice avalanche activity in the Mount Cook region predominates as low magnitude (<1000 m 3 ), high frequency events (1-8 events/h) from steep cliff-type glaciers (Iseli, 1991), producing a significant hazard on many of the well known climbing routes during the summer ablation season (Irwin et al, 2002).…”

Paraglacial rock-slope stability

“…Observable triggers are most common for active paraglacial slope failures, which are mostly deep-seated gravitational slope deformations (McLean, 1976;Bovis, 1982;Bovis, 1990;Blair, 1994;Bovis and Stewart, 1998;Corsini et al, 2005;El Bedoui et al, 2009;Le Roux et al, 2009;Gischig et al, 2010). Monitoring of such features has provided insight into some of the drivers of slope deformation, and allows calibration of slope stability models for back-analyses of failure initiation during early deglaciation.…”

“…The combination of rapidly uplifting and tectonically damaged rock, steeply incised terrain and high precipitation and seismicity contribute to mass movement being a dominant form of erosion and landscape modification (e.g. Hovius et al, 1997;Korup et al, 2004 features have been observed and documented in several places (Beck, 1968;Pere, 2009), and an ongoing ridge collapse and creeping rockslide have been identified in Mount Cook National Park (Blair, 1994;Hancox, 1998).…”