Armoring Protection on Earthfill Dams

Many of the nation's existing dams are still considered to have inadequate spillway capacity. Expensive remedial measures of spillway enlargement, increased reservoir capacity, and combination of these discourage many dam owners, especially private darn owners, from rehabilitating their dams. A possible alternative to expensive rehabilitation of earthen embankment dams, whose spillways are found inadequate to pass the required inflow design flood, is found in erosion protection, or armoring, of the crest and downstream slope. For this alternative one or more types of armor are placed on the crest and downstream slope, and the structure is allowed to overtop. Among the armoring options are vegetation, geotextiles, riprap, gabions, cements (roller-compacted concrete and soil cement), and prefabricated concrete blocks (cable-tied, interlocking, and wedge-shaped). A recent survey of state dam safety officials about allowing the use of armoring and overtopping is presented and discussed. In addition, the paper discusses the hydraulic and economic feasibility of using armor protection for the rehabilitation of the Tennessee Valley Authority's Chickamauga Dam. 11 pp., 10 references.