Adapting the EDuMaP method to test the performance of the Norwegian early warning system for weather-induced landslides

Abstract

Abstract. The Norwegian national landslide early warning system (LEWS), operational since 2013, is managed by the Norwegian Water Resources and Energy Directorate and was designed for monitoring and forecasting the hydrometeorological conditions potentially triggering slope failures. Decision-making in the LEWS is based upon rainfall thresholds, hydrometeorological and real-time landslide observations as well as on landslide inventory and susceptibility maps. Daily alerts are issued throughout the country considering variable size warning zones. Warnings are issued once per day for the following 3 days and can be updated according to weather forecasts and information gathered by the monitoring network. The performance of the LEWS operational in Norway has been evaluated applying the EDuMaP method, which is based on the computation of a duration matrix relating number of landslides and warning levels issued in a warning zone. In the past, this method has been exclusively employed to analyse the performance of regional early warning models considering fixed warning zones. Herein, an original approach is proposed for the computation of the elements of the duration matrix in the case of early warning models issuing alerts on variable size areas. The approach has been used to evaluate the warnings issued in Western Norway, in the period 2013-2014, considering two datasets of landslides. The results indicate that the landslide datasets do not significantly influence the performance evaluation, although a slightly better performance is registered for the smallest dataset. Different performance results are observed as a function of the values adopted for one of the most important input parameters of EDuMaP, the landslide density criterion (i.e. setting the thresholds to differentiate among classes of landslide events). To investigate this issue, a parametric analysis has been conducted; the results of the analysis show significant differences among computed performances when absolute or relative landslide density criteria are considered.

The Norwegian forecasting and warning service for rainfall- and snowmelt-induced landslides

“…The service, or some of its components, has been partly presented and described in conference proceedings and previous articles (i.e. Boje et al, 2014a;Bell et al, 2014;Piciullo et al, 2017). The service, presented herein, can be categorized as a "territorial" EWS following Calvello (2017) and as "forecasting and warning type" based on Stähli et al (2015).…”

“…The performance of the landslide service was also tested with the EduMaP (Event, Duration Matrix, Performance) method proposed by Calvello and Piciullo (2016). It has been adapted to the Norwegian landslide forecasting and warning service (taking into account the variable warning areas) and tested for Western Norway for the years 2013-2014, and the results are presented in Piciullo et al (2017). Based on the results from both methods we have started to work on the regional improvement of a landslide threshold, as has been done for Southern and Eastern Norway, contributing in the reduction of false alarms in these regions (Boje, 2017).…”

The Norwegian forecasting and warning service for rainfall- and snowmelt-induced landslides

“…The method has been adapted to the Norwegian landslide forecasting and warning service (taking into account the variable warning areas) and tested for Western Norway for the years 2013-2014. Results are presented in Piciullo et al (2017). The results show an overall good performance of the system for the 10 area analysed.…”

“…A weekly evaluation of the hazard assessment is carried out in light of observed situation, number of landslides events and confirmed hazard level. The classification criteria were presented in Piciullo et al (2017). The evaluation 20 is quality assured several weeks later using updated information about how the situation was, against what actually happened and registered events.…”

“…The service, or some of its components, has been partly presented and described in conference proceedings and previous articles (i.e. Boje et al, 2014a;Bell et al, 2014;Piciullo et al, 2017;Tiranti et al, submitted).…”