Abstract

Landsliding is the dominant mass-wasting process in humid-temperate uplands and an important regulator of sediment yield from steep-land drainage basins. Information about the magnitude and frequency distribution of landslides has been derived from aerial photography, but it has proved difficult to set limits on the long-term scaling behavior of landsliding because the requirements of spatial and temporal coherence and the large number of observations necessary to undertake magnitude versus frequency analyses are not easy to fulfill. We use a 2250-yr-long record of hillslope erosion associated with extreme hydrologic events preserved in sediments from Lake Tutira, New Zealand, to investigate scaling in landslide deposits. Both the magnitude versus frequency distribution of sediment layers attributed to landsliding and the distribution of time intervals between landsliding events take the form of power laws, the former with an exponent b = 2.06 and the latter with an exponent b = 1.4. These results suggest that the erosional events originate from a self-organized critical process, and are in agreement with observations of scaling in turbidite deposits and grain flows in controlled laboratory experiments. The implications are that the aggregate behavior of landsliding at the catchment scale is orderly and that the stratigraphic record preserves a unique, long-term perspective on a fundamental geomorphic process and the extreme hydrologic events that trigger it.

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