Rainfall thresholds for shallow landslides triggering in El Salvador

El Salvador is a country that is geologically young in most of its territory, with steep slopes covered with unconsolidated volcanic sediments. It is frequently affected by extreme weather events and it also has the highest population density in Central America, which makes it very vulnerable to landslides. Therefore, predicting when landslides will occur it is necessary, and rainfall thresholds are a useful tool for that purpose. In this study, thresholds represented by cumulated rainfall (E, in mm) and duration (D, in hours) for shallow landslide initiation in El Salvador have been generated, with the objective of using them in the future in a national landslide early warning system. The thresholds have been delineated with the CTRL-T code (Melillo et al, 2018), which automatically reconstructs the rainfall conditions that triggered the landslides and determines thresholds at different non-exceedance probabilities. Rainfall data from an automatic rain gauge network and landslide data occurred in the period of 2004 to 2019 were used. A validation of the thresholds with the procedure introduced by Gariano et al (2015) has been conducted, using rainfall and landslide data for the year 2020. There are not previous ED thresholds at national level created for El Salvador, so a comparison with global and national thresholds from other countries was done.

References

Gariano S.L., Brunetti, M.T., Iovine, G., Melillo, M., Peruccacci, S., Terranova, O., Vennari, C., Guzzetti, F. (2015). Calibration and validation of rainfall thresholds for shallow landslide forecasting in Sicily, southern Italy. Geomorphology 228:653–665.

Melillo, M., Brunetti, M. T., Peruccacci, S., Gariano, S. L., Roccati, A., & Guzzetti, F. (2018). A tool for the automatic calculation of rainfall thresholds for landslide occurrence. Environmental Modelling & Software, 105:230-243.