General Design Standards for Rain Gardens

This storm water BMP is a shallow circular or informally designed planting area with a very limited sized drainage basin, a concave cross section, a defined holding capacity, an improved soil structure that will encourage rapid infiltration, and capable of supporting perennial wetland plants as shown in the Wetland Plant List or turf grass growing to a tall grass state and mowed no more often than once a month.  The rain garden shall be designed to be at least twelve (12) inches in depth and no more than twenty-four (24) inches deep with shallow sloping sides not to exceed a thirty (30) percent slope. The micro-detention shall have inflow and overflow capability. The purpose of the micro-detention is to soak up common overland flow at a proscribed capture rate (CR) determined by the Director of Landscape & Forestry.

Rain gardens shall be a minimum size of a ten (10) foot radius planted with facultative or wetland plants consisting of grasses, sedges, rushes, ornamental ground covers, flowering, deciduous or evergreen shrubs.

 

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