The Anatomy of Rain Garden đި
At its simplest⌠A rain garden is a shallow, planted depression designed to catch and hold stormwater. Instead of letting runoff skim across your property and into the sewers, a rain garden slows it down and soaks it into the ground.
A well-built rain garden includes the inflow where the water enters, the basin where the water collects, the plants, and the overflow where the water can spill out safely and intentionally. The inflow might be a downspout extension, a swale or dry creek cut into a slope, or an existing, well-established depression in the landscape. The basin or the sunken bowl that holds the water is typically layered with a mix of gravel, soil, and mulch for infiltration. The rooted native plants that we choose can handle both wet feet and dry spells. The overflow is the escape hatch. If a huge storm comes through there needs to be a plan. Sometimes the topography will already offer an effective overflow. Oftentimes, we will carve a spillway that gently directs the excess away from homes and structures.
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Sunken vs. Bermed Rain Gardens
A sunken rain garden is the simplest and most open style because you excavate a basin but you donât surround it with berms. Because of this, it accepts water from all directions. These types of rain gardens use the natural topography to drain toward the basin, so it works best when the site already has a low point where water gathers.
A bermed rain garden still starts with a dug basin, just like the sunken style but you build raised berms (or small hills) along one or more sides. Those berms:
- Hold water on slopes
- Can increase the capacity of your rain garden
- Shape how water enters the basin
- Prevent water from spilling out the wrong direction
- Allow you to create a rain garden even when the land doesnât naturally collect water
Berms are perfect for when we encounter sloped yards without a perfect existing depression in the landscape. Earth-shaping berms is very common when we have a defined inflow point and a defined overflow point. An inflow pointâfor example, a dry creek! We often run our dry creek beds directly into a rain gardenâŚ
A rain garden is one of the few investments that benefits you, your neighbors, and your entire city all at once. They reduce flooding on your property and beyond, help out your cityâs systems, improve water quality downstream, and replicate natural systems within the neighborhood!