ROCKEFELLER REFUGE GULF SHORELINE PROTECTION DEMONSTRATION

摘要

Currently, 25 to 35 square miles of wetlands are lost each year along coastal Louisiana. The shoreline along the Rockefeller Wildlife Refuge in Cameron Parish is experiencing some of the highest rates of loss, with estimates of long-term shoreline retreat ranging from 30 to 40 ft/year (Byrnes et ah 1995). To combat the direct loss of wetlands at Rockefeller Refuge, the Louisiana Office of Coastal Protection and Restoration (OCPR) teamed with the National Marine Fisheries Service (NMFS) and Louisiana Department of Wildlife and Fisheries (LDWF) to implement the Rockefeller Refuge Gulf Shoreline Stabilization Project. The project intent is to halt erosion along the 9.2 mile portion of the Refuge west of Joseph Harbor Bayou. Due to the challenges presented by extremely soft soils, requirement to protect the marsh shoreline for up to hurricane conditions, and limited construction budget, a smaller demonstration project utilizing three alternative designs was proposed and constructed in Fall/Winter of 2009. The alternatives constructed include: gravel beach fill, light-weight aggregate core breakwater, and a low crested "reef breakwater. Following construction, a monitoring plan was implemented to assess the ability of the three alternatives to combat erosion along the shoreline. The monitoring plan was designed to collect a comprehensive set of data to document the performance of the alternatives for one year following construction. A metocean data station was installed at the project site to collect wave, wind, and tide data for 6 months. Concurrent measurements of waves offshore and leeward of the breakwaters were conducted to assess wave transmission. In addition, the project area was surveyed approximately every four months to document the structure geometry, shoreline and nearshore profile changes, and structure settlement. The later was performed by surveying settlement plates that were installed during construction. In addition, a separate control area near the project location was surveyed to assess shoreline retreat with no shoreline protection. Aerial photography was obtained during each survey to visually document the conditions during the surveys.