Coastal vegetation planting projects for tsunami disaster mitigation: effectiveness evaluation of new establishments

Coastal vegetation acts as a natural barrier against extreme natural and anthropogenic activities, protecting infrastructure and human lives. Establishment of hard infrastructure for tsunami protection is not feasible in developing countries due to its cost-intensive nature. Coastal vegetation can therefore be a feasible alternative for tsunami and general coastal protection in developing countries. This study investigates the effectiveness of current coastal vegetation projects and reports a pilot-scale vegetation project, which provides insights into the management and sustainability of such projects. Thirty-seven establishments of coastal vegetation for tsunami protection were identified for the study from Hambantota to Colombo along the southern coast in Sri Lanka. Evaluation was carried out to assess whether the coastal vegetation establishments fulfilled the planning objectives, such as vegetation alignment to tsunami direction, tree density and tree species, and whether monoculture or mixed species are grown. The study also assessed continuous maintenance and awareness about coastal vegetation, community participation and long-term institutional support from government, nongovernment groups, academic institutions, and other institutions within an integrated framework. Approximately 50% of the sites were found to be effective in terms of fulfilling the above requirements and had reasonable protection against future tsunami-type events. Continuous maintenance is ensured only for 35% of sites with community participation. The survey also revealed the importance of adopting scientific and nonscientific methods of vegetation establishment and selecting appropriate species and structure of vegetation strips for tsunami protection. It is expected that this will lead to the development of coastal vegetation guidelines for local authorities.