A process, phenomenon, or human activity that may cause loss of life, injury, other health impacts, property damage, social and economic disruption, or environmental degradation
Hazard
Hazards predominantly associated with natural processes and phenomena
Natural hazards
Hazards of atmospheric, hydrological, or oceanographic origin
Hydrometeorological hazards?
Hazards that originate from internal Earth processes
Geological or geophysical hazards
Hazards of organic origin or conveyed by biological vectors, including pathogenic microorganisms, toxins, and bioactive substances
Biological hazards
Hazards induced entirely or predominantly by human activities and choices. They typically do not include armed conflicts or social instability
Anthropogenic hazards
Hazards that originate from technological or industrial conditions, dangerous procedures, infrastructure failures, or specific human activities.
Technological hazards
Hazards that may include chemical, natural, and biological hazards, often created by environmental degradation or physical/chemical pollution in air, water, or soil
Environmental hazards
Hazards originating from sources located outside the site area of interest (ex: 2004 Indian Ocean Tsunami – earthquake in Banda Aceh, Indonesia, affected coastal communities of other countries)
External hazards
An initial hazard followed by a chain of interrelated hazards (ex: earthquake triggers a landslide → the landslide triggers flooding → flooding triggers further landslides)
Cascading hazard
What are hazard interrelationships?
The mode in which one hazard affects another hazard
The occurrence of one hazard increases the likelihood and/or magnitude of additional hazards in the future (ex: forest fires can amplify the triggering of debris flows during heavy rain)
Amplification relationship
One hazard causing another hazard to occur. Any natural hazard might trigger zero, one, or more secondary hazards, which may be the same or different from the primary hazard
Triggering relationship
Two different natural hazards impact the same time period and spatial area, creating a footprint with spatial and temporal characteristics that differ from the component single hazards
Compound relationship
What are the types of multi-hazards (Tilloy et al., 2019)?
Independent
Triggering
Change conditions
Compound
Mutual exclusion
type of multi-hazards: Hazards occur independently but may coincide spatially/temporally.
Independent
type of multi-hazards: Two hazards show negative dependence.
Mutual exclusion
type of multi-hazards: Different hazards result from the same primary event.
Compound
type of multi-hazards: One hazard changes the probability of another by altering underlying conditions.
Change conditions
type of multi-hazards: Primary hazard causes a secondary hazard.
Triggering
Two or more unrelated natural hazard events that can affect human life or property (ex: area may be susceptible to flooding, bushfires, and fault rupture)
Cumulative hazards
A volcanic eruption causes ash fall, which triggers localized roof collapses, followed by rapid snowmelt or heavy rain causing mudflows (lahars) that destroy downstream communities.
Volcanic eruption chain
Large wildfires destroy vegetation → soil becomes unstable → massive debris flows or landslides during subsequent heavy rain.
Wildfire-landslide sequence
A hurricane (primary) causes storm surge → coastal flooding → power grid failure → release of toxic materials from industrial sites (Natech disasters).
Example: Hurricane Katrina, 23 August 2005, New Orleans, Louisiana, Mississippi, Alabama.
Tropical cyclone cascading consequences
