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Impacts of the North Atlantic Oscillation on Landslides
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Resumo(s)
Western Iberia landslides are mostly triggered by rainfall, as, in fact, are
most landslides worldwide. Results obtained using empirical relationships between
rainfall amount and duration, and slope instability show that critical rainfall conditions
for failure are not the same for different types of landslides.While rapid debris
flows are usually triggered by very intense showers concentrated in just a few hours,
shallow translational soil slips are most commonly triggered by intense precipitation
falls within the 1–15 days long range. On the contrary, activity of the more
deeply-seated landslides of rotational, translational and complex types is related to
successive weeks of nearly constant rainfall, over periods of 30–90 days. Largescale
patterns such as the El Niño and the North Atlantic Oscillation (NAO) change
slowly and have been shown to have an impact in both the precipitation regime and
the temporal occurrence of different landslide types in different areas of the world.
In this work a particular attention is devoted to the impact of NAO on the landslide
events that have occurred in the region located just north of Lisbon between 1956
and 2010. Results show that the large inter-annual variability of winter precipitation
observed in Portugal is largely modulated by the NAO mode. The application of a
3-month moving average to both NAO index and precipitation time series allowed
the identification of many months with landslide activity as being characterized by
negative average values of the NAO index and high values of average precipitation
(above 95 mm/month). Landslide activity in the study area is related to both intense,
short duration precipitation events (1–15 days) and long-lasting rainfall episodes
(1–3 months). The former events trigger shallow translational slides while the later
episodes are usually associated with deeper and larger slope movements. The association
between the NAO and landslide activity is shown to be more evident for the
group of deep seated landslide events.
Descrição
Palavras-chave
Landslides Rainfall triggering Thresholds NAO
Contexto Educativo
Citação
Zêzere J.L., & Trigo R.M. (2011) Impacts of the North Atlantic oscillation on landslides. In: Vicente-Serrano S., Trigo R. (eds). Hydrological, socioeconomic and ecological impacts of the North Atlantic Oscillation in the Mediterranean Region. Advances in Global Change Research, vol 46. Springer, Dordrecht. DOI: 10.1007/978-94-007-1372-7_14.
Editora
Springer