Using Fine-Grained Sediment and Wave Attenuation as a New Measure for Evaluating the Efficacy of Offshore Breakwaters in Stabilizing an Eroded Muddy Coast: Insights from Ca Mau, the Mekong Delta of Vietnam

Offshore breakwaters can be effective in reducing the energy of incident waves through dissipation, refraction or reflection. Breakwaters are increasingly constructed to stabilize eroded muddy coasts, particularly in developing countries. Accumulation of fine-grained sediment and wave attenuation are two attributes of a stable muddy coast. Effective interventions in stabilizing eroded muddy coasts include two important elements: accumulation of fine-grained sediment and wave reduction. The efficacy of offshore breakwaters in stabilizing eroded muddy coasts is, however, not yet adequately understood. A crucial question needing attention is whether accumulation of fine-grained sediment and wave attenuation should be used in evaluating the efficacy of these offshore breakwaters in stabilizing eroded muddy coasts. To address this issue, a pile-rock offshore breakwater in Huong Mai, Tieu Dua of Ca Mau, Vietnam was selected as an appropriate example in this regard. Accumulation of fine-grained sediment and wave attenuation were tested as means to investigate the efficacy of the Huong Mai structure in stabilizing the eroded muddy coast. The study was undertaken using field-based measurements and semi-structured interviews in three stages between October 2016 and December 2020. We found that this structure has had limited efficacy in stabilizing the eroded muddy coast. The structure was effective in dissipating the energy of incident waves, but we found no evidence of fine-grained sediment accumulation due to an inappropriate structural design. There was also no monitoring system in place, leading to difficulties in evaluating its efficacy in terms of wave attenuation and accumulation of fine-grained sediment. The gaps between the shoreline and the structure have not been adequately explained, resulting in substantial challenges in replicating the structure elsewhere. The Huong Mai structure should be strengthened using supplementary measures and granulometric tests in order to improve the efficacy in stabilizing eroded muddy coasts. The methods in this study provide new insights in this regard

Current Management of Allocated Mangroves for Livelihood Improvement in the Mekong Delta, Vietnam: Knowledge Gaps and a Potential Model for Future Management

The paper aims to critically review the current management of mangrove forests allocated to local communities for protecting and using mangrove forests for livelihoods in the Mekong Delta of Vietnam, and to outline a prospective model guidelines. Allocated mangrove forests were severely eroded. Private coastal lands have been intensively used for agriculture or aquaculture. Allocated mangroves and private lands need to be sustainably managed, especially to adapt to projected sea level rise in the region. The review revealed that allocated mangrove forests were poorly managed without technical guidelines on configuring allocated mangrove forests in many coastal provinces the Mekong Delta. The Kien Giang communities have recently established a future management step with developing model guidelines on configuring mangrove areas at the 30/70 ratio. The model guidelines are expected to overcome some of the challenges to the current management of allocated mangroves in Kien Giang and the Mekong Delta, but first testing in the local circumstance in Kien Giang for effectiveness and efficiency prior to wider application and policy change

Configuration of Allocated Mangrove Areas and Protection of Mangrove-Dominated Muddy Coasts: Knowledge Gaps and Recommendations

Mangrove-dominated muddy coasts have been allocated for developing livelihood models, particularly in developing countries. Uncontrolled allocation causes the mangrove forests to be vulnerable and even severely eroded. Restoration of vulnerable and eroded coastal areas has been merely conservation-driven, leaving livelihood-oriented mangrove forests unprotected. As a consequence, mangrove-dominated muddy coasts have not been well-protected. How livelihood-oriented mangrove forests are configured towards protecting coasts and protecting local livelihoods remains a challenge. This study employed a critical review for addressing this matter. The results reveal that there is limited practical knowledge of configuring livelihood-oriented models for protecting the coasts. The configuration process reported in this study is merely based on technical recommendations in South East Asia to date. The recommended configuration commences with the first stage of voluntarily designating a certain percentage of allocated forests on the seaward side to protect coasts, relocating livelihood models in the gaps among current stands of mangrove forests landward. Abandoned ponds are ecologically restored using sediment trapping structures for providing suitable substrate for promoting regrowth of local mangrove species as the second stage, followed by designation of an appropriate percentage as mangrove belts on the seaward side. The two-step configuration is highly likely to be replicable and applicable nationally and regionally due to full consideration of different political, sociocultural, and environmental characteristics in Vietnam and Indonesia

Developing a framework for integrating local and scientific knowledge in internationally funded environment management projects: case studies from Kien Giang Province, Vietnam

Local and scientific knowledge, when adequately and properly integrated, produces enormous benefits for natural resource management in comparison to a single knowledge system being used. Adequate and proper integration has major constraints that include ineffective use of the integrated knowledge, thoroughly inclusive processes, and true public participation. A six-stage framework is developed using the results and conclusions of two case studies regarding sustainable management of eroding mangrove-dominated muddy coasts in Vam Ray, Hon Dat district, Kien Giang Province, Vietnam. The framework does not stop with the creation of integrated knowledge, but should undergo a longer process. The new knowledge developed in this framework is the understanding gained and lessons learnt during the testing of products of multiple knowledge systems in a local context rather than products of integrated knowledge systems themselves. The Vam Ray framework promotes a high level of participation, effective use of products of multiple knowledge systems, maximum integration of local and scientific knowledge, local ownership, and sustainability. Therefore, the Vam Ray framework adds a new dimension to the literature in relation to integration of local and scientific knowledge in natural resource management

Mangrove transplantation in Brebes Regency, Indonesia: lessons and recommendations

Despite repeated efforts to transplant mangroves to stop coastal erosion, the Brebes coasts were severely eroded between 2010 and 2013. Effective coastal erosion control in Brebes is not possible if the current situation is not adequately addressed and problems not properly identified. This study applied participatory action research methods for critically reviewing current mangrove transplantation projects in Brebes Regency, Indonesia. Mangrove transplantation has had limited success in restoring Brebes eroding coasts. Inefficient nursery operation, the wrong choice of mangrove species, improper transplantation techniques, poor coastal protection, and inadequate ongoing monitoring and evaluation significantly contributed to the limited success. Inadequate monitoring and evaluation meant that few lessons were learnt and the same mistakes continued to be made. Recommendations for production of mangrove seedlings, mangrove transplantation techniques, and monitoring and evaluation are provided to ensure effective mangrove transplantation in the future in Brebes Regency, Indonesia

Mangrove allocation for coastal protection and livelihood improvement in Kien Giang province, Vietnam: constraints and recommendations

A management policy adopted by the Kien Giang Province, Vietnam, is to allocate mangroves areas using contracts with local community members who are dependent on mangrove resources for both mangrove protection and livelihood improvement. However, community members have not made the best use of the allocated areas, and mangroves have not been well protected. The policy is due to be revised in late 2016, as is legally required. This study used mixed methods to review the policy and its implementation with respect to mangrove protection requirements and use of mangroves for livelihood improvement and to provide recommendations for sustainable mangrove management in Kien Giang. The policy and its implementation is demonstrated to be a constraint to achieving its goal. Limited understanding of the policy of contractees resulted in ineffective and inefficient aquaculture and mangrove protection in almost all areas. Permitted thinning and selective harvests led to the creation of substantial gaps and disconnections in the established mangroves, making the entire coastline vulnerable to coastal erosion. Improper technical guidance on the configuration of mangrove allocations, and mangrove protection and transplantation methods resulted in the mangrove protected areas being fragmented and vulnerable to erosion. Permitted thinning and selective harvest practices should be reviewed to ensure adequate resilience and protection of mangrove areas, especially on critically eroding areas. Proper law enforcement should be put in place to ensure contracts are adequately implemented. Allocation and/or transferal of areas less than 1 ha must be discontinued in the future to avoid further defragmentation and degradation. Technical guidance on configuring allocated mangrove areas should be established and incorporated into the updated policy that would help improve the effectiveness of the policy, and address problems relating to strengthening resilience and protection of mangrove areas in Kien Giang Province, Vietnam. Similar programs using mangrove area allocation to individuals and households in response to mangrove area loss exist elsewhere in the Mekong delta. Understanding the reasons for the very limited success of the Kien Giang program and local co-investigation in drawing lessons learnt can help guide other similar programs elsewhere in the Mekong Delta region

Existing strategies for managing mangrove dominated muddy coasts: knowledge gaps and recommendations

Mangrove dominated muddy coasts (MDMCs) throughout the world have been made vulnerable to erosion by human induced and natural factors. Meanwhile, their management has not been clearly identified in the literature. This study uses a comprehensive literature review to describe strategies, specifically designed to manage MDMCs for effectiveness, and provides recommendations for sustainable management of these coasts. Only a small percentage of previous studies deals with real-world management of MDMCs. Two approaches that are specifically designed to manage MDMCs are science-based approaches and local knowledge-based approaches. Both approaches, each having advantages, have had limited success in effectively managing MDMCs, with a low level of local involvement, and a minimal integration of the different knowledge systems. MDMCs and their management should be distinguished from other types of coasts to avoid possible confusion in the literature. Mechanisms are needed for integrating different knowledge systems for effectively managing MDMCs. These mechanisms should promote a high level of integration of local and scientific knowledge, local ownership, and sustainability

Protected mangrove forests and aquaculture development for livelihoods

The coastal province of Kien Giang exposes some of the challenges of mangrove-based aquaculture (MBA) and coastal protection, both within the Mekong Delta and more broadly. Kien Giang was therefore selected as a case study to explore in detail the relationship between MBA and mangrove protection. This was achieved through a combination of spatial analysis of coastline change from Google Earth imagery, ground truthing and field visits, semi-structured interviews, participatory community meetings, and focus group interviews. The results indicate that the current MBA does not guarantee mangrove protection. The current MBA strategies are shown to be sustainable on stable or progradational coasts, where ponds are adequately protected by 700 m wide mangrove belts. However, ponds developed on erosional coasts commonly fail, and frequently accelerate coastal retreat as the degraded mangrove belts less effectively protect the coast. Therefore, the legislation, or its implementation should be revised to ensure that mangrove allocations for MBA can only be allowed where the shoreline is stable or prograding, and where protection is provided by minimum 40 m wide mangrove belts. As mangrove forests on the Mekong Delta face additional threats associated with rising sea levels and climate change, the revision of current practices is critically urgent

Ecological and human health risk assessments of cyanotoxins and heavy metals in a drinking water supply reservoir

Human beings are frequently exposed to a mixture of chemical pollutants through the ingestion of contaminated drinking water. The present study aimed to assess the ecological and human health risks associated with the contamination of cyanotoxins and heavy metals in a drinking water supply reservoir, the Tri An Reservoir (TAR), in Vietnam. Results demonstrated that the concentrations of individual heavy metals varied in the following order: iron (Fe) > lead (Pb) > arsenic (As) > zinc (Zn). Although the ecological potential risk of heavy metals was low during the study period, the concentration of Fe sometimes exceeded the Vietnamese standard for drinking water. Toxic cyanobacteria and microcystins (MCs) frequently occurred in the TAR with the highest density of 198.7 × 103 cells/mL and 7.8 μg/L, respectively, indicating a high risk of health impacts to humans. The results of the study indicate that exposure to heavy metals does not pose any non-carcinogenic health risks for both adults and children. However, the contamination of MCs in the surface water posed a serious disease enhancement to both adults and children through direct ingestion and dermal absorption. HIGHLIGHTS The ecological and human health risks associated with the contamination of cyanotoxins and heavy metals were investigated.; Water was contaminated with cyanotoxins and iron.; The potential risks of heavy metals were low, but the concentration of cyanotoxins indicated a high risk to human health.; This study highlights the ecological and human risks from exposure to mixtures of pollutants.