*''R'' = ''A<sub>c</sub>''/''A<sub>p</sub>''; the ratio of contributing drainage area (''A<sub>c</sub>'') to permeable paving area (''A<sub>p</sub>''). Note that the contributing drainage area (''A<sub>c</sub>'') should not contain pervious areas. R should not normally exceed 2. | *''R'' = ''A<sub>c</sub>''/''A<sub>p</sub>''; the ratio of contributing drainage area (''A<sub>c</sub>'') to permeable paving area (''A<sub>p</sub>''). Note that the contributing drainage area (''A<sub>c</sub>'') should not contain pervious areas. R should not normally exceed 2. |