icient Pavement. Asphalt 0.95 Turf, Flat (0- 1% slope) 0.25 Pavement, Concrete 0.95 Turf, Average (1 - 3% slope) 0.35 Pavement, Brick 0.85 Turf, Hilly (3 - 10% slope) 0.40 Pavement, Gravel 0.75 Turf, Steep (> 10% slope) 0.45 Roofs, Conventional 0.95 Vegetation, Flat (0 - 1% slope) 0.10 Roo