Vegetated Geogrids

A key should be dug at the bottom of theslope and into the bank to prevent scour.A filter fabric is then placed on thegraded slope, and covered in layers withstones from the key up to the top of theslope. If the top of the slope isunvegetated, vegetation can be plantedto increase erosional resistance and toadd to the aesthetic and ecological valueof the project. The cost of a rip rap isapproximately $50/cy - $100/cy. Highlyskilled labor is not required for theconstruction of rip-rap slopes.Once in place, rip-rap slopes typicallyrequire minimal maintenance. Aftersignificant storm events, slopes shouldbe checked to ensure that a significantprotective layer remains. Repairs ifrequired will typically consist of thereplacement of lost material.AdaptabilityRip-rap structures have long life spansand are self adjusting. Since thestructures are composed of small, easilymovable stones, when any damageoccurs or rocks are misplaced, the rocksstill present fall into and fill the spaces.Overtopping and scour are importantdesign considerations which may beexacerbated under sea level risescenarios. Modification of a rip-rapstructure to address these concerns isstraightforward, and consists of addingmaterial in critical areas.AdvantagesRip-rap slopes have many advantagesover other engineered shore protectionapproaches, among them are:• They are flexible and can mold to thecurvature of the stream bank.• They are more economical thanlarger stone structures.• They are flexible and have thecapability to self-adjust.• They can be used for relatively highvelocity flows.• They are extremely adaptable.DisadvantagesRip-rap has many disadvantagescompared to other engineered shoreprotection approaches, among them are:• Heavy equipment can be required forconstruction.• Rip-rap slopes provide lessprotection than many other hardapproaches.• Moving ice can remove largequantities of stone at once.Similar TechniquesAlternatives may include: revetments,gabions, and jack fields.DRAFT