Vegetative Filtering Selection Guide
Channel Ultra- Parking Roads Residential Pervious Rooftops
Grass Channel No No Maybe Maybe Yes Maybe
Dry Swale No Maybe Ideal Ideal Yes Maybe
Wet Swale No Maybe No No Maybe Maybe
Filter Strip No Maybe Yes Yes Ideal Yes
Ideal: physically, economically best alternative for site
Maybe: depends upon space available, soils, water table, etc.
No: seldom or never suitable
Notes:
Although as a group, vegetative filters can be applied to a diverse range of development conditions, individual designs are limited to a much narrower range. These common development situations include ultra-urban sites, parking lots, road and streets, small residential subdivisions and backyard/rooftop drainage. The table in this slide is a matrix that illustrates the most economical and feasible vegetative filtering designs for each of these five broad categories of development, as well as those that are not applicable.
The linear nature of streets and highways make the grass channel an excellent choice for this kind of development. A grass channel usually fits within the right of way, and is a relatively simple adaptation of the drainage channel that is usually provided anyway. In residential subdivisions, the preferred design is the dry swale. When designed properly, the design blends into the landscape and has relatively low maintenance requirements. The filter strip is considered the most ideal option for dealing with rooftop runoff and lawns in residential areas. The design can effectively treat stormwater quality at low cost with only minor changes in site grading, assuming land is available.