Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Nat. Hazards Earth Syst. Sci., 18, 1037-1054, 2018
https://doi.org/10.5194/nhess-18-1037-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
04 Apr 2018
Regional rainfall thresholds for landslide occurrence using a centenary database
Teresa Vaz, José Luís Zêzere, Susana Pereira, Sérgio Cruz Oliveira, Ricardo A. C. Garcia, and Ivânia Quaresma Centre for Geographical Studies, Institute of Geography and Spatial Planning, Universidade de Lisboa, Lisbon, 1600-276, Portugal
Abstract. This work proposes a comprehensive method to assess rainfall thresholds for landslide initiation using a centenary landslide database associated with a single centenary daily rainfall data set. The method is applied to the Lisbon region and includes the rainfall return period analysis that was used to identify the critical rainfall combination (cumulated rainfall duration) related to each landslide event. The spatial representativeness of the reference rain gauge is evaluated and the rainfall thresholds are assessed and calibrated using the receiver operating characteristic (ROC) metrics.

Results show that landslide events located up to 10 km from the rain gauge can be used to calculate the rainfall thresholds in the study area; however, these thresholds may be used with acceptable confidence up to 50 km from the rain gauge. The rainfall thresholds obtained using linear and potential regression perform well in ROC metrics. However, the intermediate thresholds based on the probability of landslide events established in the zone between the lower-limit threshold and the upper-limit threshold are much more informative as they indicate the probability of landslide event occurrence given rainfall exceeding the threshold. This information can be easily included in landslide early warning systems, especially when combined with the probability of rainfall above each threshold.

Citation: Vaz, T., Zêzere, J. L., Pereira, S., Oliveira, S. C., Garcia, R. A. C., and Quaresma, I.: Regional rainfall thresholds for landslide occurrence using a centenary database, Nat. Hazards Earth Syst. Sci., 18, 1037-1054, https://doi.org/10.5194/nhess-18-1037-2018, 2018.
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Short summary
This work proposes a comprehensive method to assess rainfall thresholds for landslide initiation using centenary landslide and rainfall data. The method includes the identification of critical rainfall related to each landslide event, the calculation and calibration of rainfall thresholds and the evaluation of rain gauge spatial representativeness. Results show that thresholds based on a probabilistic approach are highly recommended and can be easily included in early warning systems.
This work proposes a comprehensive method to assess rainfall thresholds for landslide initiation...
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