Rain gardens soak up rainwater from the downpipe, driveway and lawn. As it rains, it fills up and temporaily ponds before the water soaks away. Rain gardens not only water themselves, they also excel at reducing pollutants (fertilizers, zinc off the roof, bird droppings, etc) and help reduce chances of localised flooding.
Areas where water pools in heavy rain can be turned into rain gardens. These mini-wetlands hold water for hours or 1-2 days after heavy rain, letting it gradually drain into the soil so it’s filtered before entering waterways. Roof stormwater can also be diverted into raingardens.
On sandy soil, make a depression lower than the surrounding area, with gently sloping sides. The size of the raingarden depends on the amount of water it will get. Plant it up with natural wetland plants like rushes, sedges and flaxes, or groundcovers like leptinella and gunnera. A rock or pebble mulch is good, as bark mulch can float away when the area fills with water.
On heavier soils, raingardens might need an underdrain and/or an overflow. For more information see here.
Swales: On slopes, swales (ditches cut crossways across a sloping bank) help slow the flow of water, which lets it sink into the soil rather than running off.
Plants as filters: The bush acts as a natural water holder and filter, releasing water slowly over time. Compare a valley of sodden bush with a valley of pasture – you’ll see far more soil erosion and dirtier streams in the farmland. We can’t all have bushclad properties, but even on a small section, plantings of shrubs and grasses hold and filter water better than paved areas or lawns.