1. Italian National Landslide Warning System
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Italian National Landslide Warning System
Mauro Rossi , Ivan Marchesini
Mauro Rossi
Istituto di Ricerca per al Protezione Idrogeologica, CNR (Via Madonna Alta, 126, Perugia, Italia)
Ivan Marchesini
Istituto di Ricerca per al Protezione Idrogeologica, CNR (Via Madonna Alta, 126, Perugia, Italia)

2. Italian National Landslide Warning System
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Outline
Early-warning system structure
Data Input
Rain gauge data quality
Algorithms for the calculation of critical levels
Algorithms for combined forecasts
System outputs and validation procedure
Conclusions and future developments
We start describing the early-warning system structure; then I’ll show the data in input and the relative procedure implemented to evaluate the data quality. I will then briefly describe the algorithms for the calculation of landslide critical levels and for the calculation of landslide critical/susceptibility combined levels. I will describe the system outputs and the validation procedure, and finally I will conclude discussing the future development.
M. Rossi & I. Marchesini

3. Italian National Landslide Warning System
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system ARCHITECTURE
The system compares rainfall measurements and rainfall estimates with empirical rainfall thresholds.
Input and Storage
Analysis
Output and Delivery
The system is based on the comparison of quantitative rainfall measurements and forecasts with empirical rainfall thresholds for possible landslide occurrence. The image shows the logical-framework for the system, which is composed of three main parts: (1) for data input and storage, (2) for analysis, and (3) for the production and delivery of the results.
The system can handle geographical and meteorological data. System outputs are available through the Web with a restricted access in different formats (standard OGC services, WebGIS interfaces, pdf bulletins). Most of the system procedures are based on Open Source software.
M. Rossi & I. Marchesini

4. Rainfall measurements
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Rainfall measurements
Rainfall (mm)
Cumulated Rain (mm)
Time (April 2004) 10 8 6 4 2
250
200
150
100 50 12 14 16 18
Every hour, rainfall measurements from 1950 rain gauges are stored in the system.
Every hour, the system receives rainfall measurements from rain gauges of the national network of the Italian National Department for Civil Protection.
The map shows the geographical locations of the rain gauges. On average there is one gauge every 150 square kilometer, but the density varies. The histogram shows an example of the rainfall information stored in the system.
M. Rossi & I. Marchesini

5. Italian National Landslide Warning System
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Rainfall forecasts
Every 12 hours, 72-hour rainfall forecasts produced by a Local Area Model (LAMI) are stored in the system.
3-h Cumulated Rainfall
Every 12 hours, the system receives 72-hour rainfall forecasts produced by the Local Area Model for Italy, run by the Italian National Department for Civil Protection. The image illustrates a typical output of the meteorological model, with colours showing the cumulated rainfall predicted over a 3-hour period.
M. Rossi & I. Marchesini

6. Quality of rainfall datA
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Quality of rainfall datA
To evaluate the reliability of the rain gauges, the Cumulated Annual Precipitation (CAP) is compared to the 30-year Mean Annual Precipitation (MAP).
It is important that the system uses reliable, near real time rainfall measurements. To evaluate the reliability of the rain gauges, the total annual precipitation of each gauge was compare to the mean annual precipitation (in the 30-year period ). Empirical rules were used to detect anomalous gauges.
M. Rossi & I. Marchesini

7. Quality of rainfall data
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Quality of rainfall data
The map to your right shows the anomalous rain gauges compared to all rain gauges, shown to the left. The majority of the anomalous gauges are characterized by delay in data transmission during an event.
M. Rossi & I. Marchesini

8. Italian National Landslide Warning System
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Rainfall threshold
The system uses a single ID empirical threshold defined using a Frequentist approach.
The threshold corresponds to a 1% exceedence probability level.
Log(Duration), log(D)
Duration, D [h]
Log(Mean Intensity), log(I)
Mean Intensity, (I) [mm/h]
SF1: I = 4.3 D-0.58
At present, the system uses a single threshold of the mean intensity–duration type. The threshold was defined using a frequentist statistical approach and corresponds to an exceedence probability of 1%.
This means that of all the known intensity-duration conditions that have resulted in landslides in Italy, only one per cent is below the threshold.
M. Rossi & I. Marchesini

9. Italian National Landslide Warning System
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Italian National Landslide Warning System
Critical levels
>>
< =
Mean Intensity, (I) [mm/h]
>
Well above the threshold
<<
Above the threshold
Based on this single 1% threshold, we separate the Duration- Intensity space in five domains (considering different exceedance probabilities: 0.005%, 0.5%, 1.5%, 5%), which are used to define five warning levels. The dark green area shows conditions well below the 1% threshold. In the red area conditions are well above the threshold. The yellow area is the on the threshold domain, and the remaining domains are below the threshold and above the threshold. In the red and orange domains landslides are expected; and in the green domains landslides are not expected.
On the threshold
Duration, D [h]
Below the threshold
Well below the threshold
M. Rossi & I. Marchesini

10. Critical levels for rain gauges
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Critical levels for rain gauges
For the rainfall measurements, the critical threshold level is obtained examining the values for the previous 24, 48, 72 and 96 hours. If the level for the 24 hour rainfall is the largest, then this level is taken as the critical level. Else, the critical level is a weighted mean of all the levels, with weights decreasing linearly with time.
M. Rossi & I. Marchesini

11. Critical levels for rain gauges
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Critical levels for rain gauges
A similar procedure was adopted to calculate the critical levels for the rainfall forecasts, but using 24 and 48-hour forecasts. If the level for the 24 hour forecast is the largest, then it is taken as the critical level. Else, a weighted mean is performed.
M. Rossi & I. Marchesini

12. Critical levels for alert zones
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Critical levels for alert zones
Critical levels are then aggregated spatially using the subdivision in “alert zones” decided by the Department of Civil Protection.
When the critical levels for all rain gauges are calculated, we aggregate the information spatially. For the geographical aggregation we use a subdivision in “alert zones” decided by the Department of Civil Protection.
M. Rossi & I. Marchesini

13. Critical levels for alert zones
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Critical levels for alert zones
Modal value
Maximum value
Two aggregation criteria are used based on the maximum or the modal values. In the first case, the alert zone critical level is the largest value attributed to any rain gauge in that alert zone. In the second case, the most represented level at the different rain gauges is attributed to the alert zone.
M. Rossi & I. Marchesini

14. Italian National Landslide Warning System
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A forecast
Brembilla,
27 April 2010.
A few landslides,
12 people evacuated.
Maximum value
Landslide
Rain gauge
This is an example of a forecast, for 27 April Two online newspapers reported information on landslides occurred near the town of Brembilla, in northern Italy, where 12 people were evacuated. The enlargement shows the location of the landslides (black dot) that occurred near the rain gauge with the largest critical level.
M. Rossi & I. Marchesini

15. Italian National Landslide Warning System
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Italian National Landslide Warning System
Another forecast
Log(Mean Intensity), log(I)
Log(Duration), log(D)
Duration, D [h]
Mean Intensity, I, [mm/h]
Forecast for 1 March 2011
One landslide fatality
This is another forecast, for March 1st, The map shows the forecast at the individual rain gauges and in the alert zones. That day, there were inundations and several landslides in the Adriatic and the Ionian sectors, and one landslide fatality near Reggio Calabria caused by a debris flow. This was a correct forecast.
M. Rossi & I. Marchesini

16. Italian National Landslide Warning System
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Validation
Validation is important, but difficult to perform.
Lack of information on landslide occurrence in an area does not mean that landslides have not occurred in an area.
Validation is an important part of the system, but it is difficult to perform because lack of information on landslide occurrence in an area does not mean that landslides have not occurred in that area, necessarily.
M. Rossi & I. Marchesini

17. Italian National Landslide Warning System
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Validation
The collection of information on rainfall events with landslides in the last few years was done to validate the rainfall thresholds used by the system and the system algorithms for the calculation of critical levels.
The systematic collection of information on rainfall events that have resulted in landslides in the last few years will allow for validation of the system.
Two types of validations are possible:
1 – The first is the validation of the rainfall thresholds for the possible initiation of landslide. At present only the national threshold used by the system was validated.
The second is the validation of the system algorithms for the calculation of critical levels.
Both the validations were performed successfully considering landslides in the Abruzzo region from April to September An extensive validation of the system has still to be performed.
M. Rossi & I. Marchesini

18. Italian National Landslide Warning System
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combined FORECAST
To consider the real instability predisposition of the territory, the system generates critical/susceptibility combined levels, using the susceptibility zonation of the Italian territory.
Critical levels don’t consider directly the real instability predisposition of the territory. To account that the system calculates critical/susceptibility combined levels. These are obtained multiplying the landslide susceptibility (S) for the exceedance probability (Psup) of the rainfall Intensity-Duration conditions associated to rainfall events. Actually they are calculated similarly to critical levels, since they are calculated by the weighted mean of the multiplication of susceptibility (S) and the exceedance probability (Psup) associated to the rainfall for different antecedent or forecast periods.
M. Rossi & I. Marchesini

19. Italian National Landslide Warning System
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combined FORECAST
For the rainfall measures
For the 24hr rainfall forecast
For the 48hr rainfall forecast
These levels are obtained multiplying the landslide susceptibility (S) for the exceedance probability (Psup) of the rainfall Intensity-Duration conditions associated to rainfall events. Actually they are obtained similarly to critical levels, since they are calculated by the weighted mean of the product of susceptibility (S) and the exceedance probability (Psup) associated to the rainfall for different antecedent or forecast periods.
M. Rossi & I. Marchesini

20. Italian National Landslide Warning System
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Italian National Landslide Warning System
combined FORECAST
Exceedance probability
Susceptibility ×
Basically the values of the Italian landslide susceptibility model obtained at the national scale using data from the AVI archive (Archivio Aree Vulnerate Italiane) are multiplied by the the exceedance probabilities associated to rainfall events to obtain the combined levels.
M. Rossi & I. Marchesini

21. Italian National Landslide Warning System
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combined FORECAST
Combined levels
Critical levels
This is an example of the levels calculated by the system. Comparing the combined levels with the critical ones some differences can be observed:
Along plains and close to the pre-alpine reliefs the combined levels are much lower due to low susceptibility values associated to flat areas (municipalities along the plain);
In some alpine areas combined levels are slightly lower than the critical levels, this because the normalization effect related to the low susceptibility values of these areas;
In the Liguria region combined levels and critical levels are similar because the high susceptibility levels characterizing these areas.
M. Rossi & I. Marchesini

22. Combined levels for alert zones
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Combined levels for alert zones
Mean value
Maximum value
Similarly to critical levels, the critical/susceptibility combined levels are aggregated spatially in the alert zones. Two aggregation criteria are used: the first associates to the alert zone the average of the levels inside itself, the second the maximum value. Unreliable rain gauges are excluded from the calculation.
M. Rossi & I. Marchesini

23. Italian National Landslide Warning System
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System outputs
The main system outputs, that consist of critical levels for more than 2100 rain gauges and for 134 alert zones, are calculated every day at 12:00 UTC+00.
The system generates maps of critical levels, published on the web as OGC (Open Geospatial Consortium) services (WMS, WFS, WCS).
The early warning system outputs are generates every day at 12:00 UTC and they are delivered to the National Civil Protection Authorities.
Maps of critical levels are generated by the system, and they are published as standard OGC (Open Geospatial Consortium) web services (WMS, WFS, WCS) by the IRPI CNR spatial data infrastructure.
M. Rossi & I. Marchesini

24. Italian National Landslide Warning System
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Web GIS interface
To facilitate the use of the system by the Civil Defence personnel, we have designed a specific web site. The site is password protected, and gives access to all current and past forecasts.
M. Rossi & I. Marchesini

25. Italian National Landslide Warning System
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Daily bulletin
In addition the system automatically prepares a bulletin with all the information generated by the system. This information is at the national scale, and for all the 20 Italian Regions. The bulletin is sent via to the Civil Protection personnel.
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26. Italian National Landslide Warning System
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Advancements needed
Several problems affect the system:
Higher temporal resolution
Use of new regional / local thresholds
Integration of different rainfall forecasts
Better validation procedures
Better integration of landslide susceptibility
Integration with vulnerability criteria
The system still have several problems and difficulties related to the use of a simple, threshold-based model for the operational forecasting of rainfall induced landslides at the national scale. To overcome some of these problems, several possible advancements, will concern:
The increase of the temporal resolution (the system should issue forecasts every 6 hours),
The adoption of new regional and local thresholds,
An integration of different rainfall forecast models,
Better validation procedures,
An improved integration of landslide susceptibility, and
The integration of vulnerability criteria.
M. Rossi & I. Marchesini

27. Italian National Landslide Warning System
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Final remarks
A distance remains between science & technology and their application to operational landslide forecasting.
The Italian landslide early warning system remains – and will remain in the near future – an experimental system.
A significant distance remains between science & technology, and their application to successful operational landslide forecasting at the national scale, to reduce the human consequences of slope failures.
With this respect, the Italian landslide early warning system remains – and will remain for a while – an experimental system, but helpful to mitigate landslide risk to the population in Italy.
M. Rossi & I. Marchesini

28. Italian National Landslide Warning System
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References
Brunetti M.T., Peruccacci S., Rossi M., Luciani S., Valigi D. Guzzetti F., Rainfall thresholds for the possible occurrence of landslides in Italy. Natural Hazards and Earth System Sciences, 10, 447–458. Guzzetti F., Peruccacci S., Rossi M., Stark C.P., The rainfall intensity-duration control of shallow landslides and debris flows: an update. Landslides, 5(1), 3-17, doi: /s Guzzetti F., Peruccacci S., Rossi M., Stark C.P., Rainfall thresholds for the initiation of landslides in Central and Southern Europe. Meteorology and Atmospheric Physics, 98, Rossi M., Peruccacci S., Brunetti M.T., Marchesini I. et al., SANF: a national warning system for rainfall-induced landslides in Italy. Proceedings 11th International & 2nd North American Symposium on Landslides, June 2-8, 2012, Banff, Alberta, Canada.
M. Rossi & I. Marchesini