No abstract

Ho Chi Minh City (HCMC) is facing notably high levels in current and future flooding. Simultaneously, the ongoing process of rapid industrialization is characterized by the strong emergence of manufacturing firms within the urban area. As manufacturing firms are at the frontline regarding damage caused by flooding, which is often neglected in risk analyses, we argue that the assessment of firms' exposure to flooding is essential for implementing an integrative flood risk governance. Hence, this study maps manufacturing firms in HCMC, using geocoding based on the Vietnam Enterprise Census (2005, 2015), and assesses whether they are exposed to future sea level rise. The maps developed visualize the expansion of manufacturing firms from 2005 to 2015 and the spatial distribution of firms exposed to future sea level rise in HCMC. Our results reveal that particularly domestic, private micro firms in labor-intensive industries, which represent the backbone of the local economy, are exposed, threatening their competitiveness and viability.

Abstract. The risk of urban flooding is a major challenge for many megacities in low elevation coastal zones (LECZ), especially in Southeast Asia. Here, the effects of environmental stressors overlap with rapid urbanization, which significantly aggravates the hazard potential in these regions. Ho Chi Minh City (HCMC) in Southern Vietnam is a prime example of this set of problems and therefore a meaningful study case to apply the concept of low-regret disaster risk adaptation as defined by the Intergovernmental Panel on Climate Change (IPCC). In order to explore and evaluate potential options for hazard mitigation, a hydro-numerical model was employed to scrutinize the effectiveness of two adaptation strategies: (1) a large-scale flood protection scheme as currently constructed in HCMC and (2) the widespread installation of small-scale rainwater detention as envisioned in the framework of the Chinese Sponge City Program (SPM). A third adaptation scenario (3) assesses the combined implementation of both approaches (1) and (2). From a hydrological point of view, the reduction of various flood intensity proxies suggests that the effectiveness of large-scale flood protection outweighs that of small-scale rainwater storage by far. For example, an assessment of the Normalized Flood Severity Index (NFSI) suggests a potential flood reduction that is 3.5 times higher for a classic infrastructure solution than for the Sponge City approach. In contrast, the number of manufacturing firms that are protected from risk after the implementation of disaster risk adaptation significantly excels for the latter response option: while the ring dike mitigates flooding at about 20 % of all considered locations, the assumed rainwater detention would protect up to 93 %. And also, from a governance perspective, decentralized rainwater storage conforms better to the low-regret paradigm: while the large-scale ring dike depends on a binary commitment (to build or not to build), decentralized small- and micro-scale solutions can be implemented gradually (through targeted subsidies) and add technical redundancy to the overall system. In the end, both strategies are highly complementary in their spatial and temporal reduction of flood intensity, so local decision-makers may specifically seek multi-faceted strategies, avoiding singular approaches and designing adaptation pathways in order to successfully prepare for a deeply uncertain future.

Adaptive governance approaches emphasize the crucial role of the private sector in enabling climate change adaptation. Yet, the participation of local firms is still lacking, and little is known about the conditions potentially influencing firms’ adaptation decisions and mechanisms that might encourage private sector engagement. We address this gap with an empirical analysis of the willingness of manufacturing small- and medium-sized enterprises (SMEs) to participate financially in collective flood adaptation in Ho Chi Minh City (HCMC), a hotspot of future climate change risk. Using scenario-based field experiments, we shed light on internal and external conditions that influence potential investments in collective initiatives and explain what role SMEs can play in flood adaptation. We find that direct impacts of floods, perceived self-responsibility, and strong local ties motivate firms to participate in collective adaptation, whereas government support, sufficient financial resources, and previously implemented flood protection strategies reduce the necessity to act collectively. Here, opportunity costs and the handling of other business risks play a decisive role in investment decisions. This study shows that although private sector engagement appears to be a promising approach, it is not a panacea. Collective initiatives on flood adaptation need formal guidance and should involve local business networks and partnerships to give voice to the needs and capacities of SMEs, but such initiatives should not overstretch firms’ responsibilities.

Abstract. Urban flooding is a major challenge for many megacities in low-elevation coastal zones (LECZs), especially in Southeast Asia. In these regions, the effects of environmental stressors overlap with rapid urbanization, which significantly aggravates the hazard potential. Ho Chi Minh City (HCMC) in southern Vietnam is a prime example of this set of problems and therefore a suitable case study to apply the concept of low-regret disaster risk adaptation as defined by the Intergovernmental Panel on Climate Change (IPCC). In order to explore and evaluate potential options of hazard mitigation, a hydro-numerical model was employed to scrutinize the effectiveness of two adaptation strategies: (1) a classic flood protection scheme including a large-scale ring dike as currently constructed in HCMC and (2) the widespread installation of small-scale rainwater detention as envisioned in the framework of the Chinese Sponge City Program (SCP). A third adaptation scenario (3) assesses the combination of both approaches (1) and (2). From a hydrological point of view, the reduction in various flood intensity proxies that were computed within this study suggests that large-scale flood protection is comparable but slightly more effective than small-scale rainwater storage: for instance, the two adaptation options could reduce the normalized flood severity index (INFS), which is a measure combining flood depth and duration, by 17.9 % and 17.7 %, respectively. The number of flood-prone manufacturing firms that would be protected after adaptation, in turn, is nearly 2 times higher for the ring dike than for the Sponge City approach. However, the numerical results also reveal that both response options can be implemented in parallel, not only without reducing their individual effectiveness but also complementarily with considerable added value. Additionally, from a governance perspective, decentralized rainwater storage conforms ideally to the low-regret paradigm: while the existing large-scale ring dike depends on a binary commitment (to build or not to build), decentralized small- and micro-scale solutions can be implemented gradually (for example through targeted subsidies) and add technical redundancy to the overall system. In the end, both strategies are highly complementary in their spatial and temporal reduction in flood intensity. Local decision-makers may hence specifically seek combined strategies, adding to singular approaches, and design multi-faceted adaptation pathways in order to successfully prepare for a deeply uncertain future.