We installed this two-tiered rain garden in a Baltimore city front yard to collect and manage runoff from 2 downspouts and a sump pump. The rain garden was designed with two bioretention cells to deal with the slope of the yard and prevent an excessively high berm at the low end. Cedar logs were used to tier the two cells which allowed the water to overflow from one cell to the next.
This specific rain garden can capture about 240 gallons of runoff from the downspouts during a 1” storm and an additional 375 gallons from the sump pump.
