Mashes Sands Erosion Control Project
MRD conducted a wave, hydrodynamic and sediment transport modeling study to determine the sediment transport rates and pathways. Shoreline and volume changes were calculated, and a sediment budget was developed for the study area. Extensive sea grass beds were identified within the project influence and mapped. The sediment transport modeling assisted in assessing the performance of the design alternatives and the potential impacts to these sea grass beds.
MRD evaluated design alternatives and ranked them in order of viability to meet the study’s goals. A beach restoration with Terminal Groin was selected to increase storm capacity, mitigate historic erosion trends, and minimize impacts to the sea grass beds. The beach would be widened by 100 feet along the 1,800 foot shoreline to enhance the recreational opportunities of the County Park. The beach quality sand dredged from the Mashes Sands boat ramp and Sunrise canals will be used as the source of sand for the beach fill project.
In addition, MRD assessed the dredging protocol of the County’s boat ramp channel and recommend alternatives to reduce the frequency and maintenance dredging costs. Based on the coastal analysis, a “sand-tight” 200-foot long terminal groin was selected and constructed to reduce the 50,000 yds3 shoaling rate into the navigation channel. The structure designed based on the CEM and was sited to minimize impacts to the adjacent wetlands and sea grasses.
MRD was responsible for project implementation including design, permitting and construction phase services for the terminal groin. The groin is estimated to have reduced the shoaling rate into the channel by 80%.