Identifying gaps in research on social vulnerability to floods: a systematic review of indicators, indexes, and methodological approaches

Abstract Social vulnerability plays a critical role in shaping the impacts of flooding, yet the ways in which it is measured remain inconsistent and often disconnected from local realities. As climate-related flood events intensify globally, there is an urgent need to understand how social vulnerability is conceptualized and assessed to inform more equitable and effective risk reduction strategies. This paper reports the results of a systematic literature review on indicators and indexes used to assess social vulnerability to floods. Utilizing the PRISMA methodology, we identified and screened 1621 studies published between 2013 and 2023, selecting 36 peer-reviewed publications for examining how social vulnerability indices have been conceptualized, constructed, and applied, as well as the range of indicators, and methodological approaches used. We identified 78 indicator sets across 22 thematic domains. Results indicate that most attention has been given to a small set of indicators focusing on at-risk populations, socioeconomic factors, housing, and employment, while other factors such as health conditions, disaster preparedness, social connectedness, gender minorities, and sexuality are consistently underrepresented. Many studies rely on established frameworks without adapting them to local socio-cultural contexts and use census and secondary data sources, providing limited household-level and qualitative insights. Lack of methodological transparency, particularly regarding normalization and weighting, is common as is insufficient validation and ground-truthing. Greater attention to these issues, along with empirical case studies, is needed to provide in-depth insights into the root causes of social vulnerability and inform policies better tailored to local realities. This review highlights significant conceptual and methodological gaps, calling for more context-sensitive, mixed-method, and empirically validated approaches to improve the robustness and local relevance of social vulnerability assessments in flood-prone areas.