Subsurface infiltration beds

 An infiltration bed is a vegetated bed where the rainwater is retained temporarily until it has seeped into the soil. The vegetated area is designed with a top soil layer suitable for vegetation and with sand/gravel underneath which is suitable for infiltration. To manage overflow in connection with extreme rain, adjacent to the infiltration bed, an area may be designed which is suitable for infiltration and detention of the rainwater. Furthermore, a dry well may be installed beneath the infiltration bed.

Infiltration beds are useful in many places, e.g. near homes, industry, in shopping areas and carparks. The surface of infiltration beds may vary. Often, the surface is directly vegetated with plants; however, it may also be covered by a layer of gravel/small stones. With a layer of small stones, the bed will require less maintenance. However sand and waste will often infiltrate the stones and eventually cause the soil below the stones to grow more compact and, thus, gradually reduce the possibility for water to seep through.

An infiltration bed can be established in a corner of the garden, along flagged paths or as a separate bed in the lawn. In public spaces, infiltration beds can be laid along roads, in the central reservation, and in carparks to mark the line between parking spaces, or as larger beds covering areas between buildings.