10 (Brown 2011),“assess risk of policy” (Lempert _et al._ 2004; Carter _et al._ 2007; Dessai _et al._ 2007), and “vulnerability and robust response. An emerging literature has begun to assess strengths and weaknesses of these approaches -- see, for instance Hall et al. (2012) and Hallegatte et al. (2012). In the future, this literature will help decision makers better determine which robustness analysis to use when faced with deeply uncertain and complex decision challenges. This report uses RDM because it offers a set of analytic tools (such as scenario discovery) that work easily with an agency’s existing planning models and a participatory process that we have found particularly useful.<sup>5</sup> Nonetheless, all these new approaches share the central idea of beginning with a proposed policy or policies, running models over many cases to identify vulnerabilities of policy (policies), and using this information to identify and evaluate potential robust policy responses that address those vulnerabilities. This reports key conclusions rest on these central ideas.

Overall, decision makers should use RDM and related approaches if their decision challenge involves deep uncertainties and complex interactions among problem components. These conditions certainly seem to hold for the integrated flood risk management challenge facing Ho Chi Minh City as well as for many other decision challenges throughout the developing world.<sup>6</sup>

# **3. Workshops and Other Stakeholder Engagement**

Stakeholder engagement played an important role in this project. We organized two workshops and ongoing discussions with Steering Center for Flood Control according to the RDM “deliberation with analysis” process. As shown in Figure 2.1, these engagements were facilitated with outputs from the RDM analysis.

A meeting at Steering Center for Flood Control’s office in Ho Chi Minh City on October 3, 2011 launched the participatory scoping phase of our analysis (Step 1 in Fig 2.1) and focused on the XLRM factors discussed in Section 4. This collaborative scoping activity continued for approximately two months, resulting in a project memorandum delivered to the client at the end of November 2011.<sup>7</sup> In addition to defining the analytical problem, this scoping step builds a common understanding of the problem and relationships between stakeholders and analysts. The value of this step cannot be overstated, particularly in analyses involving participants who are geographically dispersed, speak different native languages, and bring different skills to the effort.

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> 5  Analytic tools, such as robust optimization and robust control, also employ a robustness criterion (Chandrasekharan 1996; Hansen _et al._ 2008). Such tools do not emphasize the identification of vulnerabilities and are not designed around a participatory decision support process. They can, however, prove very useful in identifying new strategies in Step 4 of an RDM analysis.

> 6 It is also important to relate approaches, such as RDM, that emphasize robust decisions to the large literature on resilience (Berkes 2007; Park _et al._ 2012).  While differing interpretations exist of the words robustness and resilience, we follow the view expressed by the IPCC (2010, p. 48) that the two are related concepts, with resilience generally taking a system-focused view and robustness taking a decision-focused view. Thus an observer outside Ho Chi Minh City might ask whether the city is resilient in the face of flood risk, but a decision-maker within the city might ask whether the particular policies they can pursue as part of this system are robust in the face of this risk.

> 7  Please contact the authors for a copy of this project memorandum.