Rain Gardens

Building Rain Gardens in an Urban Setting

Rain Gardens must be designed properly in urban landscapes to successfully managing runoff. Design considerations for including rain gardens include proper drainage, slope, location, size, soil infiltration rate, plant material and irrigation. A soil’s porosity (amount of available pore space), permeability (how interconnected pore spaces are), and infiltration rate (how quickly the water moves through the soil) are critical to the success of a rain garden and its ability to absorb stormwater. These soil properties affect the amount of air, moisture, and nutrients that are available in the root zone and how much runoff is absorbed into the ground instead of running off into the storm drain system and out to the ocean.

Plant selection must consider: size at maturity, exposure (amount of sun or shade), and tolerance of seasonal high temperature, rainfall and drought.