Vegetated Geogrids

Dune CoreApproachConstruction CostSoft Hard Low HighMaintenance CostAdaptabilityLow High Low HighDescriptionDune cores refer to the technique ofstabilizing shorelines with structurallyreinforced mounds. Although muchmore common along ocean coasts wherethe primary destructive forces are relatedto shore perpendicular waves, some ofthe concepts can and have been adaptedfor use along sheltered shorelines.Geotextile tubes, made of high strengthpolyester or polypropylene, typicallymake up the dune core. These tubes areplaced along the bank and are frequentlyburied and/or planted so as to remainhidden. The core only becomes activeduring storm events, when erosionexposes the tube. As such, this approachis not recommended on chronicallyeroding banks.of the fill material, while the strength isselected such that the tube can withstandthe high pressures experienced duringthe filling process. Fill material canconsist of either onsite or dredgedmaterial, which is pumped into the tubesthrough several injection ports. Theseinjection ports are secured after pumpingso that they are not torn and reopened bywave and current forces. Once filled,the tubes have cross sections that arecircular along the sides, and flat on top.After installation, the filled materialexperiences dewatering, which impactsthe settling of the material. The tubesmay need to be refilled to retain thedesigned crest elevation. For stability, itis essential that the filled tubes have ahigh unit weight.DRAFTFigure 24: Typical dune core cross-section.Design and ConstructionThe selection of geotextile material forcreating the dune core is based on theporosity and strength characteristics ofthe material. The porosity is selected tomatch the particle size and permeabilityFigure 25: Onsite placement of a dune core,along an ocean coastline.