What are they?
Large landscape practices are designed to capture, store, and/ or infiltrate significant quantities of stormwater using basin-like depressions in the ground. Unlike flood control basins, which quickly release water from all but the largest storms, these types of practices may be designed to drain down slowly over a period of one to three days. In some instances, they may be designed as permanent wet ponds or wetland systems to provide nutrient cycling and water filtration through natural chemical processes. Drainage stones, piping and sand layers can be engineered into these systems to optimize their functionality. During large storms, overflow from these practices may be piped into the storm sewer system or discharge directly via overflow structures into nearby water bodies. During dry periods, the appearance of these features – planted with trees, shrubs and grasses – approximates low lying meadows or woodlands. These naturalized systems can provide significant habitat for birds and pollinators like bees and butterflies.
When are they used?
Large landscape green infrastructure practices can be used to manage large volumes of stormwater, for example from a neighborhood development project or a large commercial site. They may be designed to extend or accentuate existing natural features in recreational areas along bike trails or walking paths, or simply to enhance the natural character of the development. These types of systems are most likely to be incorporated into a landscape plan along edge areas, slightly offset from walkways and roads. They are most often planted with naturalistic meadow-type grasses, trees, and shrubs.
What are some key considerations?
- Subsurface components need to be cleaned occasionally, so it is important that these systems be designed with safe and easy maintenance access.
- For settings in wooded areas, protection of plants from wildlife is important during the early stages of establishment. Deer fencing (to protect small trees in particular) and muskrat trapping (for ponds and wetlands) can help to prevent wildlife damage.
The following large landscape practices are described in further detail in this section:
- Naturalized Detention Basin*
- Constructed Wetlands*
- Infiltration Basin
- Wet Pond (naturalized edge and water re-use)*
Further information on green infrastructure design standards can be found in the NJ BMP Manual.
*These three techniques, while recognized as best practices in NJ DEP BMP Manual, are not viewed by NJ DEP as green infrastructure.