Multiple-hazards and their interactions in urban low-to-middle income countries: a case study from Nairobi

Global policy frameworks, such as the Sendai Framework for Disaster Risk Reduction 2015-2030, increasingly advocate for multi-hazard approaches across different spatial scales. However, management approaches on the ground are still informed by siloed approaches based on one single natural hazard (e.g. flood, earthquake, snowstorm). However, locations are rarely subjected to a single natural hazard but rather prone to more than one. These different hazards and their interactions (e.g. one natural hazard triggering or increasing the probability of one or more natural hazards), together with exposure and vulnerability, shape the disaster landscape of a given region and associated disaster impact.  Here, as part of the UK GCRF funded research grant “Tomorrow’s Cities” we first map out the single natural hazardscape for Nairobi using evidence collected through peer-reviewed literature, grey literature, social media and newspapers. We find the following hazard groups and hazard types present in Nairobi: (i) geophysical (earthquakes, volcanic eruptions, landslides), (ii) hydrological (floods and droughts), (iii) shallow earth processes (regional subsidence, ground collapse, soil subsidence, ground heave), (iv) atmospheric hazards (storm, hail, lightning, extreme heat, extreme cold), (v) biophysical (urban fires), and vi) space hazards (geomatic storms, and impact events). The breadth of single natural hazards that can potentially impact Nairobi is much larger than normally considered by individual hazard managers that work in Nairobi. We then use a global hazard matrix to identify possible hazard interactions, focusing on the following interaction mechanisms: (i) hazard triggering secondary hazard, (ii) hazards amplifying the possibility of the secondary hazard occurring.  We identify 67 possible interactions, as well as some of the interaction cascade typologies that are typical for Nairobi (e.g. a storm triggers and increases the probability of a flood which in turn increases the probability of a flood). Our results indicate a breadth of natural hazards and their interactions in Nairobi, and emphasise a need for a multi-hazard approach to disaster risk reduction.