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.