A drainage structure having perforated parallel top and bottom plates ( 5 & 6 ) separated by spacer members ( 7 ). A web ( 15 ) joins adjacent spacer members ( 7 ) and has a curved profile ( 17 ) such that water spilling over the web ( 15 ) does so, at a varying velocity profile to increase oxygenation of the water. This drainage structure ( 1 ) can also be filled with good drainage soil ( 42 ) and planted with grass ( 4 ) to filter and retain water that passes therethrough, with a layer of filter medium ( 42 ) below and a water permeable drain ( 1 & 24 ) below the filter medium ( 42 ), to transport water into the substrate and into a reticulation tank ( 57 ) where the water can percolate back into the soil.
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