Do all roads lead to Sapporo? The role of linking and bridging ties in evacuation decisions

Abstract

Why do some communities evacuate long-distances in higher rates than others after disaster? This mixed-methods study uses a new dataset of long-distance evacuation rates after Hokkaido's Eastern Iburi Earthquake in September 2018, aggregated to the city level from geolocated Facebook user movement. We found that communities with stronger linking and bridging social capital tended to see much lower evacuation rates to distant towns. We used statistical models, fieldwork, and content analysis of 12 interviews, finding that despite rumors on social media, communities with stronger linking social networks had greater trust in government and decided to stay in local evacuation shelters. This was especially the case if these communities also had stronger bridging social networks, helping them access key information, especially among vulnerable communities. Meanwhile, residents with weaker linking or bridging networks may have believed rumors of extreme water, food, and power shortages and left town for good. This study highlights the importance of trust in local officials when managing evacuation after disasters.

The Road More Traveled: Evacuation Networks in the US and Japan

“…Gehlot et al (2019) found that residents with wider social networks traveled further when evacuating. Similarly, past studies of Facebook-related evacuation data found that individuals with stronger bridging and linking ties evacuate more (Fraser et al, 2020; Metaxa-Kakavouli et al, 2018).…”

“…While not an all-encompassing measure of social vulnerability, wealth reflects a major social barrier for evacuation. Finally, to represent social capital, I use new Social Capital Indices for Japanese municipalities from 2017 (Fraser et al, 2022) and new social capital indices for US county subdivisions from 2018 (Fraser, Page-Tan, et al, 2022), based on Kyne and Aldrich’s (2020) Social Capital Indices for US counties. Third, the US and Japanese indices have demonstrated considerable external validity, consistently showing the same associations with key disaster outcomes as expected by literature, even in different national contexts (e.g., Fraser, 2021; Fraser, Cunningham, et al, 2021; Fraser, Page-Tan, et al, 2022; Kyne & Aldrich 2020).…”

“…Social capital refers to the social ties that connect neighbors, friends, coworkers, and even elected officials, building trust, reciprocity, and enabling collective action and good governance (Putnam, 1993, 2000; Szreter & Woolcock, 2004; Tsai, 2007). Over the last two decades, scholars have linked communities with stronger social capital to better disaster response and recovery outcomes (Aldrich, 2012; Fraser et al, 2022). Studies suggest that while bonding ties among members of the same social, ethnic, or income groups help those groups recover better, bridging ties among members of different groups help entire communities share resources and recover, while linking ties to elected officials can help residents’ needs get heard and facilitate the distribution of public goods to those who need it (Aldrich & Meyer, 2015).…”

“…In particular, bridging and linking ties tend to have multiplicative effects on recovery, helping everyone access public goods they need (Aldrich et al, 2018; Smiley et al, 2018; Aldrich 2019), while strong bonding and linking ties helps specific social groups access those resources at the expense of others (Aldrich & Crook, 2008). Recent research has shown that stronger bridging and linking social ties likewise boost evacuation (Collins et al, 2017; Fraser et al, 2022; Metaxa-Kakavouli et al, 2018), aided by their expansive and diverse social networks (Gehlot et al, 2019; Sadri et al, 2017). These social ties (not to be confused with the mobility networks this study examines as its outcome) might affect evacuation.…”

“…While past studies (Fraser et al, 2022; Huang et al, 2016; Metaxa-Kakavouli et al, 2018; Riad et al, 1999) have examined why some communities evacuate more than others, and others have approximated evacuation behavior through models and simulations of past crises (Moussaïd et al, 2016; Zhao et al, 2020), this study is the first to analyze the mobility network of evacuation among a complete population: Facebook users. With network data, two new questions can be examined: First, does evacuation tend to be clustered around the same highly interconnected locales, or dispersed among many diverse locales?…”