Sand Sealing of Coastal Structures

DISCUSSION: Rubblemound coastal structures contain voids between individual armor units. Structure voids maximize turbulent wave energy dissipation, but also allow passage of water and sediment. The volume of sediment passing through some jetties and terminal groins can be substantial, resulting in increased channel shoaling, higher maintenance costs, and significant loss of beach material. Most sediment infiltration problems are recognized from the resultant sediment distribution pattern. However, measuring the quantity of sediment infiltrating the structures is difficult. The extent of sand infiltration may be measured through visual observations, surveys, dredging records, aerial photographs, sediment traps, and dye tracers. "Sand sealing" refers to techniques which make coastal structures impervious to sand infiltration. These techniques vary from the use of grout or sheetpiling, to building additional structures. Each sealing method is utilized to reduce structure permeability. However, decreasing structure permeability may increase runup and overtopping, wave reflection, and structure instability.