Rivers represent one of the main conduits for the delivery of plastics to the sea, while also functioning as reservoirs for plastic retention. In tropical regions, rivers are exposed to both high levels of plastic pollution and invasion of water hyacinths. This aquatic plant forms dense patches at the river surface that drift due to winds and currents. Recent work suggests that water hyacinths play a crucial role in influencing plastic transport, by efficiently trapping the majority of surface plastic within their patches. However, a comprehensive understanding of the interaction between water hyacinths and plastics is still lacking. We hypothesize that the properties relevant to plastic transport change due to their trapping in water hyacinth patches. In particular, the length scale, defined as the characteristic size of the transported material, is a key property in understanding how materials move within rivers. Here, we show that water hyacinth patches trap on average 54%–77% of all observed surface plastics at the measurement site (Saigon river, Vietnam). Both temporally and spatially, we found that plastic and water hyacinth presence co-occur. The formation of plastic-plant aggregates carries significant implications for both clean-up and monitoring purposes, as these aggregates can be detected from space and need to be jointly removed. In addition, the length scale of trapped plastics (∼4.0 m) was found to be forty times larger than that of open water plastics (∼0.1 m). The implications of this increased length scale for plastic transport dynamics are yet to be fully understood, calling for further investigation into travel distances and trajectories. The effects of plastic trapping likely extend to other key properties of plastic-plant aggregates, such as effective buoyancy and mass. Given the prevalence of plant invasion and plastic pollution in rivers worldwide, this research offers valuable insights into the complex environmental challenges faced by numerous rivers.

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Microbial pathogens in urban floodwaters pose risks to human health, potentially causing diseases such as diarrhea. However, the disease burden related to urban traffic exposure from citizens passing through floodwaters is not easily quantified and therefore not included in many studies. Notably, this problem has received little attention in low-to-middle-income countries, with frequent flood events and the heavy diarrheal disease burden. This article calculates the infection risks and disease burden, considering traffic associated with exposure to floodwater contaminated with rotavirus for the first time in Ninh Kieu District, Can Tho city. Can Tho city in the Vietnamese Mekong Delta is well known to have many flood events every year, with many diarrheal cases during the flood season. The methodology comprises two steps. First, we applied quantitative microbial risk assessment that proposes the inclusion of exposure to traffic due to rotavirus in floodwater. Second, the disease burden was expressed in disability-adjusted life years (DALYs). The exposed groups are child pedestrians, adult pedestrians, motorcyclists, and cyclists. We used video footage to monitor the traffic. The results show that total DALYs per flood event were 1.35 × 10⁴ for 63,390 exposed people (i.e., 2129 DALYs per 10,000 cases). Motorcyclists are the strongest contributors to the DALYs (95%), followed by cyclists (2.8%), adult pedestrians (2%), and child pedestrians (0.2%). The population in Ninh Kieu District may suffer from waterborne diseases through traffic activities during flooding times. Our approach can be applied in other areas worldwide and helps identify main risk groups and focus areas for interventions.

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The Vietnamese Mekong Delta (VMD) is an example of a complex dynamic socio-hydrological system in which societies and hydrology interact and co-evolve. The dominant engineering approach in the VMD has enhanced the dynamics of society and hydrology. This study looks at the implications of socio-hydrological dynamics in the coastal VMD where saline water is controlled by various infrastructures. In the first phase, key informant interviews and focus group discussions were used to explore socio-hydrological dynamics in the study area. The results show divergence in livelihood strategies inside the freshwater-projected area, shaping a heterogeneous agricultural landscape of fresh- and brackish-water livelihoods manifested by four socio-hydrological groups. Next, the Motivation and Ability (MOTA) framework and household surveys were used to assess the adaptability in the agricultural development pathway advocated by the freshwater policy. The result revealed differentiations among these socio-hydrological groups. The findings suggest other practices may be required to help the area navigate towards future adaptations to socio-hydrological changes.@en

Exploring whether society is sufficiently equipped and motivated to adopt planned interventions is vital for modern plan development trajectories. The Motivation and Ability (MOTA) framework offers a tool to assess the societal adoptability of plans by exploring stakeholders' motivations and abilities. It was originally developed to assess plan implementation feasibility for structural measures of flood management in the Mekong Delta. Further development is necessary before applying the tool in other contexts and for other types of planning interventions. Institutional measures like participatory water management (PWM) have long been recognized as essential elements for water management, but have so far also remained out of the reach of conventional planning assessment tools such as cost-benefit or cost-effectiveness analyses. This research, therefore, aims at extending the MOTA tool in the context of PWM reforms in Bangladesh. It does this by, first, further detailing the MOTA components and identifying indicators for quantification and, second, an expert validation and application of this framework for coastal communities in Bangladesh. Our results suggest that the MOTA framework is capable of informing policymakers and implementing agencies about how to enhance the stakeholders' motivation and ability to ensure an enduring implementation of PWM reforms.@en

This study identifies how the governance of the transition to sustainable agriculture in the Vietnamese Mekong Delta is constrained by a lack of leadership, coordination, and funding. The Vietnamese Mekong Delta region is an important agricultural region yet highly vulnerable to climate change. In 2017, the Government of Vietnam issued Resolution 120, which calls for a transition towards sustainable development and climate change resilient agriculture in the delta. We evaluated the governance of implementing this resolution using an established transition governance framework, based on policy document analysis, ethnographic observations and interviews with national government agencies and ten departments in the delta provinces An Giang and Ben Tre. The analysis indicates that delays are caused by fragmented central government leadership and that friction exists between top-down plans and bottom-up action taken by the provinces in the delta. The transition is further constrained by the absence of inter-provincial coordination and funding mechanisms. Overall, this study shows that the required governance structure exists on paper but highlights how an insufficient governance process constrains climate change adaptation in Vietnam.@en