Embodiments of the invention comprise a system for strengthening a sloped structure such as a berm, basin, levee, or embankment. The comprises first and second opposing sides, the second side being adjacent the sloped structure; a bottom side adjoining bottom edges of the first and second sides, thereby forming a cavity within the first, second, and bottom sides; fill material disposed within the cavity; an impermeable membrane encapsulating at least a portion of the fill material; and a plurality of reinforcing members disposed within the fill material.