A composite synthetic ground cover system for erosion control to be placed atop substantially non-level, sloping ground, comprising: a synthetic grass which comprises a turf backing and synthetic grass blade-like elements tufted and secured thereto and extending therefrom; an infill ballast applied to the synthetic grass atop the turf backing; and a binding agent applied to the infill ballast to protect the infill ballast against high velocity water shear forces; wherein the composite synthetic ground cover system further comprises: an impermeable backing applied to or formed on an underside of the turf backing, said impermeable backing comprising a permeable geotextile and an impermeable polymer applied to the permeable geotextile to make the backing impermeable; said synthetic ground cover system comprising an affixed composite of the impermeable backing and the synthetic grass, said impermeable backing strengthening the turf backing and the connection between the blade-like elements and the turf backing, wherein the composite synthetic ground cover system can remain in place atop substantially non-level, sloping ground despite shear forces from gravity, wind, and water flow, and wherein water present above the turf backing is prevented from penetrating the soil by the impermeable backing. a synthetic grass which comprises a turf backing and synthetic grass blade-like elements tufted and secured thereto and extending therefrom; an infill ballast applied to the synthetic grass atop the turf backing; and a binding agent applied to the infill ballast to protect the infill ballast against high velocity water shear forces; wherein the composite synthetic ground cover system further comprises: an impermeable backing applied to or formed on an underside of the turf backing, said impermeable backing comprising a permeable geotextile and an impermeable polymer applied to the permeable geotextile to make the backing impermeable; said synthetic ground cover system comprising an affixed composite of the impermeable backing and the synthetic grass, said impermeable backing strengthening the turf backing and the connection between the blade-like elements and the turf backing, wherein the composite synthetic ground cover system can remain in place atop substantially non-level, sloping ground despite shear forces from gravity, wind, and water flow, and wherein water present above the turf backing is prevented from penetrating the soil by the impermeable backing. an impermeable backing applied to or formed on an underside of the turf backing, said impermeable backing comprising a permeable geotextile and an impermeable polymer applied to the permeable geotextile to make the backing impermeable; said synthetic ground cover system comprising an affixed composite of the impermeable backing and the synthetic grass, said impermeable backing strengthening the turf backing and the connection between the blade-like elements and the turf backing, wherein the composite synthetic ground cover system can remain in place atop substantially non-level, sloping ground despite shear forces from gravity, wind, and water flow, and wherein water present above the turf backing is prevented from penetrating the soil by the impermeable backing.