Evacuation decisions in response to natural disasters: Insights from a large-scale social media survey

TL;DR

The paper addresses the complex, multi-level decision process behind evacuation during natural disasters, focusing on the 2019-2020 Australian bushfires. It combines a rapid Facebook-based survey (with rejection sampling) and Facebook Data for Good displacement maps to estimate displacement and augment mobility data, applying weighted logistic analyses and a Horvitz-Thompson framework to scale findings to the population. Key findings reveal demographic heterogeneity in evacuation timing, agency in evacuation decisions, and household-separation patterns, with distinct gender and income effects and substantial impact on work and duration of displacement. The approach demonstrates the feasibility and value of rapid-response social-media surveys to inform disaster response planning, complementing geolocation data and enhancing policy-relevant insights for transportation, housing, and relief allocation.

Abstract

Evacuation in response to natural disasters is a complex process involving multiple decision-makers at the personal, household, community, and government levels. Consequently, many disparate factors influence who evacuates, when, and how to respond to a nearby disaster. In this paper, we leverage a novel method of data collection through social media to explore the evacuation response decisions of people in areas affected by the 2019-2020 Australian bushfires. We explore the validity of this data collection method for generating plausible estimates of evacuation and its ability to supplement cell phone location data using survey responses. Ultimately, we identify several key factors influencing household decisions on evacuation, specifically focusing on the phenomenon of household members evacuating or returning from evacuation at different times.

Figures (6)

• Figure 1: Map of the bounding box survey locations: Green Wattle Creek Fire in Eastern New South Wales and the Cudlee Creek Fire in Adelaide Hills South Australia.
• Figure 2: Example survey question from the Facebook Australia Bushfire survey on the platform.
• Figure 3: Men are significantly more likely to say that the decision to evacuate was their own, while women are more likely to attribute it to the government.
• Figure 4: Women are more likely to evacuate within the same city as their home. This corresponds with trends in the Displacement Map data across many disasters and geographies.
• Figure 5: Men are significantly more likely to return home ahead of the other household members.