In terms of the hazard, the flood maps for HCMC show flood depth and extent from the river and from sea (when looking at the sea level rise scenario). Pluvial flooding and possible ‘sink’‐areas in the city are not taken into account. Moreover, the lowest return period we have flood maps for is not low, compared to what is experienced in the city. Some areas of HCMC are flooded every year. Since this analysis used a flood with a 10‐year return period as the flooding scenario with the highest recurrence interval we were not able to capture the relative differences in exposure to these yearly/bi‐annual flooding events (and we hypothesize that poor people are relatively more exposed to these types of flooding than the general population).

# **7. Policy Recommendations**

Despite the limitations, this analysis presents some initial findings on what exposure to floods looks like in Vietnam, how it may change under a changing climate, and the exposure of poor people. The results from this paper have implications regarding infrastructure development, land use planning, and strategies to manage flood risk.

First, the results of this paper suggest that climate change is likely to increase the number of people exposed to floods, especially in the Mekong and Red River Deltas. Climate change impacts can make frequent events as important as rare ones in terms of exposure: for instance, a 25‐year flood under future conditions of high sea level rise exposes more people than a 200‐year flood under current conditions. In addition to showing the benefits of investing in flood risk management today, these results also suggest that new investments in flood protection (whether natural protection through mangroves or physical protection through dikes and drainage systems) should be planned with climate change considerations (e.g. where will flood be the worst in the future and how can new infrastructure withstand future levels of flood).

However, current planning approaches in Vietnam have not yet adequately taken these existing and future floods into account (IMHEN and UNDP 2015). For example, the city of Long Xuyen in the Mekong Delta has based its dike infrastructure around the city on historical floods levels only, with no inclusion of future climate change‐induced water levels (This Report, 2016). Qualitative surveys in Long Xuyen suggest existing defenses have already proved inadequate in recent flooding (This Report, 2016). Investments in climate‐informed flood protection taken now reduce flood exposure, but can also save money in the long‐ run by reducing the amount spent on recovery and reconstruction for future floods. And while it is challenging to integrate into project planning, innovative approaches such as decision‐making under uncertainty can provide support to decision‐makers on how to design flood projection with climate change in mind (Hallegatte et al. 2012).

Furthermore, while infrastructure investment can protect certain areas, it may increase exposure in other areas. for example, upstream dams in the Mekong Delta can increase the strength and velocity of downstream floods (This Report, 2016). Thus, flood risk assessment needs to be integrated across policy sectors (agriculture, industry, infrastructure, defense, urban planning) before development decisions are made, and more comprehensive approaches, like integrated coastal zone management and planning, would help to reduce exposure of people and assets in Vietnam.

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