period flood under current socioeconomic conditions, climate change may expose 38‐46% of the population, depending on the severity of sea level rise. Climate change impacts may make frequent events as important as rare ones in terms of exposure: for instance, a 25‐year flood under future climate conditions exposes more people than a 200‐year flood under current conditions. While poor districts are not found to be more exposed to floods at the national level, the city‐level analysis of HCMC provides evidence that 68‐85 percent of slum areas are exposed to floods, a higher percentage than the rest of the city. In addition to showing the benefits of investing today in flood protection, this paper provides policy implications for the design of flood risk management strategies in Vietnam.

# **2. Literature review**

In the last 30 years, floods worldwide have killed more than 500,000 people and resulted in economic losses of more than US$500 billion (Kocornik‐Mina et al. 2015). It is therefore no surprise that a number of studies have examined the population and economic assets exposed to flood risk. At the global level, it is well documented that an increasing share of the population and economic assets lie in areas exposed to riverine and coastal flood risk today, and these trends show no sign of slowing down (UN‐ISDR 2015; Ceola, Laio, and Montanari 2014; Jongman et al. 2014). To compound these socioeconomic changes, climate change is expected to intensify many hazards and further increase exposure: the number of people exposed to river floods could increase by 4‐15% in 2030 and 12‐29% in 2080 (Winsemius et al. 2015).

But only a handful of global studies have examined how this distribution of flood exposure differs between rich and poor. Kim (2012) assesses these dynamics at the country‐level, and finds that poor countries tend to be more exposed to natural disasters, including floods, compared to rich countries. More recently, (Winsemius et al. 2015) examined whether poor people _within countries_ are more exposed to flood risk, and found that this was the case for 60% of the 52 countries sampled.

Within Vietnam, studies suggest that floods significantly impact poverty, both quantitatively at the national level using household survey data (Bui et al. 2014) and qualitatively through focus group interviews at the local level in Ho Chi Minh City (World Bank and Australian AID 2014). One study within Vietnam examines the exposure of poor and non‐poor people to floods and found that a disproportionate number of poor people live in highly‐flooded areas of the Mekong Delta (Nguyen 2011).

At a more local scale and especially within cities, land and housing markets often push poorer people to settle in riskier areas. Where markets factor in hazard risks, housing is cheaper where risk is higher (Husby and Hofkes 2015). And, because poorer people have fewer financial resources to spend on housing and a generally lower willingness and ability to pay for safety, they are more likely to live in at‐risk areas (Lall and Deichmann 2012; Fay 2005; Hallegatte et al. 2016).

Empirically, this higher exposure to flood risk for poor urban dwellers is found in about 75% of the countries examined by (Winsemius et al. 2015), and also when using high‐resolution data on household location and flood hazards in Mumbai, India (Patankar 2015). This high exposure of the urban poor to floods has severe implications on the health of children and economic outcomes of adults, as evidenced in HCMC (World Bank and Australian AID 2014).

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