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.

There have been few reviews of the effectiveness of the management of coastal mangrove protected areas and coastal land use planning at all levels in the Mekong Delta, Vietnam. Ben Tre province provides a good case study to enable the assessment of typical management practices in the provinces of the Delta. The study aims to critically review the current strategies for managing the Ben Tre coast and to consider what changes are required to ensure effective coastal management. The current coastal management strategies only dealt with symptoms and worked temporarily. There has been insufficient coordination in land use planning and coastal management among the Ben Tre government agencies, substantially contributing to mangrove loss and degradation. Natural regeneration of local mangrove species and secondary succession, although having been practically effective for protecting from coastal erosion, have not been used as coastal management measures. Three strategies, hold the existing defence line, managed realignment, and no active intervention, are recommended to assist in managing the Ben Tre coast for adaptation to climate change and sea level rise, and livelihood improvement.