Distribution of landslides in southwest New Zealand

Abstract

This study examines the size distribution of a regional medium-scale inventory of 778 landslides in the mountainous southwest of New Zealand. The spatial density of mapped landslides per unit area can be expressed as a negative power-law function of Landslide area A L spanning three orders of magnitude ($10 2 -10 1 km 2 ). Although observed in other studies on landslide inventories, this relationship is surprising, given the lack of absolute ages, and thus uncertainty about the temporal observation window encompassed by the data. Large slope failures (arbitrarily defined here as having a total affected area A L >1 km 2 ) constitute 83% of the total affected landslide area A LT . This dominance by area affects slope morphology, where large-scale landsliding reduces slope angles below the regional modal value of hillslopes, j mod $39. More numerous smaller and shallower failures tend to be superimposed on the pre-existing relief. Empirical scaling relationships show that large landslides involve >10 6 m 3 of material. The volumes V L of individual preserved and presumably prehistoric (i.e. pre-1840) landslide deposits equate to 10 0 -10 2 years of total sediment production from shallow landsliding in the respective catchments, and up to 10 3 years of contemporary regional sediment yield from the mountain ranges. Their presence in an erosional landscape indicates the geomorphic importance of landslides as temporary local sediment storage.

The CAIRN method: automated, reproducible calculation of catchment-averaged denudation rates from cosmogenic nuclide concentrations

“…For the problem of spatially heterogeneous lithology, careful geologic mapping, such as that done by a handful of recent authors (e.g., Safran et al, 2006;West et al, 2014;McPhillips et al, 2014;Carretier et al, 2015), can alleviate some of the uncertainty, but such mapping is logistically challenging. For landsliding, mass removal can be measured in the field, modeled (e.g., Niemi et al, 2005;Yanites et al, 2009), or approximated using mapped landslide inventories (e.g., Hovius et al, 1997;Korup, 2005). These may be combined with data on landslide area-volume relationships (e.g., Guzzetti et al, 2009).…”

The 20 February 2010 Madeira Island flash-floods: VHR satellite imagery processing in support of landslide inventory and sediment budget assessment

“…The difficulty resides in acquiring information on surface and sub-surface geometry for a large number of landslides, and can only be solved, at present, adopting empirical relations that link geometrical measurements, such as the individual landslide area, with its volume. Several authors have suggested that there is a relationship between the area and the volume of landslides that can be expressed through empirical formulations (Simonett, 1967;Rice and Fogging, 1971;Innes, 1983;Guthrie and Evans, 2004;Korup, 2005;ten Brink et al, 2006;Imaizumi and Sidle, 2007;Guzzetti et al, 2008;Imaizumi et al. 2008).…”

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

“…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). Large bedrock failures from glaciated areas of the Southern Alps have received greater scientific attention (e.g., Korup, 2005a;Whitehouse and Griffiths, 1983), partly because road infrastructure can be at risk (Paterson, 1996), downstream chain reactions can endanger lowland areas (e.g., Davies and Scott, 1997;Hancox et al, 2005), and recent glacial changes appear to be increasing the frequency of high magnitude events and likelihood of impacts into glacial lakes (McSaveney, 2002).…”