How to Build a Rain Garden to Capture Runoff
There are many reasons to build a rain garden. Rain gardens help filter out pollutants like bird guano from stormwater and turn them into nutrients for your garden. They help reduce the draw on local aquifers to irrigate our gardens and allow those aquifers to be replenished by the natural water cycle. Because of this, rain gardens are essential in the fight to reduce stormwater pollution’s impacts on river systems, which in turn, end up in our beloved ocean. Stormwater is one of the largest sources of environmental pollutants entering the world’s oceans today. Rain gardens can even help reduce the populations of mosquitoes and other biting insects who rely on stagnant water to breed. As climate change brings diseases like malaria further north, managing mosquito populations becomes less a luxury and more a public health necessity.
Apart from purely utilitarian reasons to build rain gardens, the hobby gardeners and organic farmers of the world will find that rain gardens also provide an opportunity to sculpt a beautiful new aesthetic which conventional gardens simply cannot match. To get started, all you need is a ruler, a level, and a calculator.
Doing The Math
Rain gardens capture the rainfall from impermeable surfaces that flows across your property. Then, using nothing more than the natural slope of the land it collects and disperses that water into the garden and out into the local watershed beyond. If done properly, this water should collect and drain away within 24 hours of any given rainfall. Of course, to capture all the water falling on your roof, driveway, patio, and other impermeable surfaces you’ll need to know roughly how much water to expect.
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