Multi-Hazard Scenarios and Dynamic Risk

Gill, J., Hussain, E., Malamud, B., and Sakic Trogrlic, R.
Tomorrow's Cities
Impact story
April 2021

In this paper, we discuss the dynamic nature of risk through the lens of multi-hazard relationships and scenarios. Disaster risk is commonly expressed as (Risk = Hazard × Exposure × Vulnerability). This expression does not communicate the extent to which each term (and therefore risk and impact) can change over time, and any relationships between the four variables. To better convey and discuss multi-hazards and dynamic risk, in July and August 2020 we held two virtual workshops (40 and 35 participants) as part of the GCRF Tomorrow’s Cities Research Hub, which has as its focus four cities Istanbul, Kathmandu, Nairobi, and Quito, with a particular emphasis on the urban poor. During the two workshops, participants (including those from academia, NGOs, and the public sector) from each city generated multi-hazard scenarios that can be used to improve the understanding of dynamic risk and we highlighted three main examples of dynamic risk: (1) The hazard term can involve multiple hazards, with relationships between hazards, and the likelihood or magnitude of single natural hazards and multi-hazard scenarios varying over time. (2) Both the exposure and vulnerability components of the risk equation change over time, and can contribute to the triggering, amplification (or reduction) of multi-hazard events. (3) Progression through multi-hazard scenarios can influence or drive changes in both exposure and/or vulnerability terms. These three statements illustrate the dynamic nature of each component of the risk equation and the existence of relationships between each term. Furthermore, they demonstrate how understanding the multi-hazard landscape and potential multi-hazard scenarios can help to enrich understanding of dynamic risk. This understanding of multi-hazard scenarios can be used to consider potential interventions where risk is dynamic.