| :Ratio of catchment (A<sub>c</sub>) to the practice footprint area (A<sub>p</sub>). ''syn.'' I/P ratio. For[[green roofs]] (and often permeable paving systems) this will be 1:1. In [[bioretention]] it may be 15 or 20 to 1. | | :Ratio of catchment (A<sub>c</sub>) to the practice footprint area (A<sub>p</sub>). ''syn.'' I/P ratio. For [[green roofs]] (and often permeable paving systems) this will be 1:1. In [[bioretention]] it may be 15 or 20 to 1. |