Rain gardens are landscaped depressions that receive stormwater runoff, allowing it to slowly infiltrate into the groundwater. This helps reduce flooding, erosion, and pollution from stormwater runoff. Rain gardens should be sized to about 20-30% of the drainage area and deep enough (around 6 inches) to temporarily store runoff from a 1-inch rainfall. The soil must have proper drainage and permeability to allow infiltration. Rain gardens provide habitat and remove pollutants from stormwater runoff through various natural processes.