  Natural hazards are becoming increasingly expensive as climate change and
development are exposing communities to greater risks. Preparation and recovery
are critical for climate change resilience, and social media are being used
more and more to communicate before, during, and after disasters. While there
is a growing body of research aimed at understanding how people use social
media surrounding disaster events, most existing work has focused on a single
disaster case study. In the present study, we analyze five of the costliest
disasters in the last decade in the United States (Hurricanes Irene and Sandy,
two sets of tornado outbreaks, and flooding in Louisiana) through the lens of
Twitter. In particular, we explore the frequency of both generic and specific
food-security related terms, and quantify the relationship between network size
and Twitter activity during disasters. We find differences in tweet volume for
keywords depending on disaster type, with people using Twitter more frequently
in preparation for Hurricanes, and for real-time or recovery information for
tornado and flooding events. Further, we find that people share a host of
general disaster and specific preparation and recovery terms during these
events. Finally, we find that among all account types, individuals with
"average" sized networks are most likely to share information during these
disasters, and in most cases, do so more frequently than normal. This suggests
that around disasters, an ideal form of social contagion is being engaged in
which average people rather than outsized influentials are key to
communication. These results provide important context for the type of disaster
information and target audiences that may be most useful for disaster
communication during varying extreme events.
