Vegetated Geogrids

fill material and transport methods.Construction costs can range from$100/lf to $200/lf. This price includesthe assembly and filling of the baskets,the wire for the baskets, the stone fill,and basket closure. Normally heavyequipment is not necessary forconstruction of a gabion wall, howeverthe labor involved with basket closure issubstantial.Once in place, it is important thatgabions are routinely checked fordamage and broken wires; however theytypically require very minimalmaintenance. The most common repairsconsist of fixing broken baskets and/orreplacing missing rocks. Any largevegetation should be removed to reducethe likelihood of the baskets breaking.Erosion around the structure must alsobe very closely monitored. Undercuttingat the toe of the structure can causefailure if appropriate remediationmeasures are not taken. Finally,locations on the gabion where runoffflows over the top of the structure cancause soil erosion and must also beclosely monitored. If regular inspectionsare performed geotechnical failure canbe avoidedAdaptabilityIn terms of adaptability gabion structuresare quite flexible. Because of theirmodular nature, gabions lend themselvesto adding units to increase their heightand/or structural resiliency.AdvantagesGabions have many advantages overother engineered shore protectionapproaches, among them are:• Gabions can be used when armorstone is too costly.• Structural integrity increases overtime with the addition of sand andvegetation.• Since the structures are flexible andpermeable, scouring is reducedcompared to solid shear structures.• The porosity of the structure allowssand and dirt to accumulate andproduce vegetation.• Gabions can withstand relativelyhigh velocity flows.• Gabion walls easily fit into thecontours of the stream bank.• Gabion walls can freeze & thaw andthe shifting of the stones will haveminimal impact to the structure.• Heavy machinery is notrequired forconstruction.• Maintenance costs are minimal.DisadvantagesGabions have many disadvantagescompared to other engineered shoreprotection approaches, among them are:• They have a limited lifespan (5-10yrs) due to the breakdown of thewire mesh used to construct thebaskets.• Ultimately they break, resulting incobbles and wire mesh scattered onthe beach. This material can pose asignificant hazard.• Many people consider gabions aneyesore.• Usage is restricted to areas of lowmoderatewave energy.• Gabions are hard structures, whichreduce the sediment supply to thebeach.• Gabions alter the nearshore habitat.• Erosion in adjacent areas may beexacerbated if the structure is notproperly designed.DRAFT