Enhancing marsh elevation using sediment augmentation: A case study from southern California, USA

Tidal marshes are an important component of estuaries that provide habitat for fish and wildlife, protection from flooding, recreation opportunities, and can improve water quality. Critical to maintaining these functions is vertical accretion, a key mechanism by which tidal marshes build elevation relative to local sea level. The beneficial use of dredged material to build marsh elevations in response to accelerating sea level rise has gained attention as a management action to prevent habitat loss over the coming decades. In January 2016, a sediment augmentation project using local dredged material was undertaken at Seal Beach National Wildlife Refuge in Anaheim Bay, California, USA, to benefit tidal marsh habitat and the listed species it supports. The application process added 12,900 cubic meters of sediment with an initial, average 22-cm gain in elevation over a 3.2-hectare site. Due to sediment characteristics and higher than anticipated elevations in some areas, vegetation colonization did not occur at the expected rate; therefore, adaptive management measures were undertaken to improve hydrology of the site and facilitate vegetation colonization. More case studies that test and monitor sea level adaptation actions are needed to assist in the planning and implementation of climate-resilient projects to prevent coastal habitat loss over the coming century.

A Cost-evaluation Technique for Restoration of Seagrass and Other Plant Communities

Coastal habitat loss must be reduced either through conservation or mitigative efforts. Implementation of mitigation depends largely on accurate cost-assessment of the projects that are involved. We centre our discussion here on seagrass transplanting as an exemplary mitigative tool.The technology of restoring seagrass communities has received increasing attention in recent years. However, the methods used have had varying degrees of success, a largely unknown factor being the cost of the technique that is used.In this paper is presented a universal format that includes consideration of the essential factors in our costanalysis, such as planning, planting, and monitoring activities, geographic location, tidal influence, labour, and materials (both expendable and non-expendable). Cost per (successfully established) shoot or seed or fruit is recommended as the best indicator of cost effectiveness for a given technique. Incorporation and presentation of this information is urged in future projects to motivate wider application of seagrass and other essential plantcommunity restoration.