Statistics of Landslide Size

The size (e.g. length, area, volume) of individual landslides varies largely. As shown in Figure 1.1, the length of landslides varies from less than a meter to several hundreds or even thousands of kilometres for submarine slides. Landslide area spans the range from less than a few square meters, for shallow soil slides, to thousands of square kilometres, for large submarine failures. The volume of single mass movements ranges from less than a cubic decimetre, for rock fragments falling off a cliff, to several hundreds of cubic kilometres, for gigantic submarine slides (Locat and Mienert, 2003), or for slope failures identified on the Moon (Hsu, 1975), Mars (McEwen, 1989) and Venus (Malin, 1992). The frequency-size distribution of landslides is important information to determine landslide hazards (Guzzetti et al., 2005a) (see § 7.3), and to estimate the contribution of landslides to erosion and sediment yield (e.g., Hovius et al., 1997, 2000; Martin et al., 2002; Guthrie and Evans, 2004b; Lavé and Burbank, 2004). For these reasons, it is essential that the distributions are quantified precisely, using accurate and reliable methods. In this chapter, after a review of the limited literature, I show how to obtain frequency-area and frequency-volume statistics of landslides from empirical data obtained from landslide inventories. I then discuss applications of the obtained frequency statistics of landslides, with examples from the Umbria region, including an application to investigate the completeness of the three landslide inventory maps available for the Collazzone area. ...