Eventi estremi

Risksv0

Responsible:Niccolò Calandri

Extreme Events — GDACS Monitoring

Overview

The Extreme Events layer provides a comprehensive risk assessment based on historical disaster data from the GDACS (Global Disaster Alert and Coordination System), managed jointly by the European Commission's Joint Research Centre (JRC) and the United Nations Office for the Coordination of Humanitarian Affairs (OCHA).

The monitoring covers six event types:

Event Type	Data Source	Key Metrics
Earthquakes	USGS/EMSC seismic networks	Magnitude (Richter), depth, PGA
Floods	GDACS flood model, satellite imagery	Affected area, severity, duration
Cyclones	JTWC, NHC, JMA	Category (Saffir-Simpson), wind speed
Volcanoes	Smithsonian GVP, VAAC	VEI, ash plume height
Droughts	GDACS drought monitor	SPI, duration, severity
Wildfires	MODIS/VIIRS, EFFIS	Burned area, FRP, duration

The overall risk is calculated through a frequency × severity matrix that classifies the area into four alert levels: Green (low risk), Yellow (moderate), Orange (significant), and Red (severe).

Calculation Methodology

Risk assessment framework:

Event retrieval — Historical disaster events within a defined radius of the analysis area are queried from the GDACS database
Frequency analysis — Event count per type over the reference period (typically 20+ years)
Severity scoring — Each event is scored based on its intensity metrics (magnitude, category, affected area)
Risk matrix computation:

	Low Severity	Medium Severity	High Severity	Very High Severity	Extreme Severity
Low frequency	Green	Green	Yellow	Yellow	Orange
Medium frequency	Green	Yellow	Yellow	Orange	Red
High frequency	Yellow	Yellow	Orange	Red	Red

Aggregation — Individual event-type risks are combined into an overall risk score
Classification — Final alert level: Green, Yellow, Orange, or Red

Data Sources

Source	Provider	Type	Coverage	Update
GDACS	JRC / UN OCHA	Event database	Global	Near-real-time
USGS Earthquake Catalog	USGS	Seismic events	Global	Continuous
MODIS/VIIRS Active Fire	NASA	Fire detections	Global	Daily
EFFIS	JRC/Copernicus	European fire data	Europe	Daily

Technical Notes

GDACS provides near-real-time alerts but historical completeness varies by region and event type
The risk matrix approach provides a standardized comparison across different disaster types
Earthquake risk assessment considers both magnitude and proximity to fault lines
Drought monitoring uses standardized precipitation indices which may have limited accuracy in data-sparse regions
The 20+ year historical window may not capture very rare catastrophic events

References

GDACS — Global Disaster Alert and Coordination System. European Commission / UN OCHA. Available at: https://www.gdacs.org/
De Groeve, T., Thielen-del Pozo, J., Brakenridge, R. (2015). "Global Disaster Alert and Coordination System". In: Shroder, J.F. (Ed.), Hazards, Risks and Disasters in Society. Elsevier.
JRC (2020). "INFORM Risk Index: Methodology". Publications Office of the European Union.

Data Sources & References

Sources

WRD_GDACS_99

Methodology

La mappa Extreme Events utilizza i dati del sistema GDACS (Global Disaster Alert and Coordination System), gestito dalla Commissione Europea JRC e UN OCHA per l'allerta precoce e il coordinamento dei disastri naturali. Il sistema monitora 6 tipologie di eventi estremi: - EQ (Earthquakes/Terremoti): dati USGS ed EMSC, disponibili dal 2002; - FL (Floods/Inondazioni): dati GloFAS e CEMS, disponibili dal 1988; - TC (Tropical Cyclones/Cicloni): dati NHC, JTWC, JMA, disponibili dal 2011; - VO (Volcanic Eruptions/Vulcani): dati Smithsonian GVP, disponibili dal 2018; - DR (Droughts/Siccità): dati SPEI Global Database, disponibili dal 2018; - WF (Wildfires/Incendi): dati VIIRS e MODIS FIRMS, disponibili dal 2020. Per ogni evento vengono estratte le geometrie di impatto specifiche (isosisme per terremoti, aree inondate, tracce dei cicloni, buffer vulcanici, perimetri incendi) e le informazioni di impatto (magnitudo, morti, sfollati, area colpita). Per l'area di interesse viene calcolato il rischio combinando frequenza storica e severità degli eventi in una matrice 3x5 (severità Low/Medium/High × frequenza da Very Rare a Very Frequent). La classificazione finale è in 4 livelli: Green (rischio basso), Yellow (moderato), Orange (alto), Red (molto alto).

Extreme Events — GDACS Monitoring

Overview

The monitoring covers six event types:

Event Type	Data Source	Key Metrics
Earthquakes	USGS/EMSC seismic networks	Magnitude (Richter), depth, PGA
Floods	GDACS flood model, satellite imagery	Affected area, severity, duration
Cyclones	JTWC, NHC, JMA	Category (Saffir-Simpson), wind speed
Volcanoes	Smithsonian GVP, VAAC	VEI, ash plume height
Droughts	GDACS drought monitor	SPI, duration, severity
Wildfires	MODIS/VIIRS, EFFIS	Burned area, FRP, duration

Calculation Methodology

Risk assessment framework:

Event retrieval — Historical disaster events within a defined radius of the analysis area are queried from the GDACS database

Frequency analysis — Event count per type over the reference period (typically 20+ years)

Severity scoring — Each event is scored based on its intensity metrics (magnitude, category, affected area)

Risk matrix computation:

	Low Severity	Medium Severity	High Severity	Very High Severity	Extreme Severity
Low frequency	Green	Green	Yellow	Yellow	Orange
Medium frequency	Green	Yellow	Yellow	Orange	Red
High frequency	Yellow	Yellow	Orange	Red	Red

Aggregation — Individual event-type risks are combined into an overall risk score

Classification — Final alert level: Green, Yellow, Orange, or Red

Source

Provider

Type

Coverage

Update

GDACS

JRC / UN OCHA

Event database

Global

Near-real-time

USGS Earthquake Catalog

USGS

Seismic events

Global

Continuous

MODIS/VIIRS Active Fire

NASA

Fire detections

Global

Daily

EFFIS

JRC/Copernicus

European fire data

Europe

Daily

Data Sources & References

Sources

WRD_GDACS_99