User:Tiffli/sandbox

http://www.missouribotanicalgarden.org/sustainability-conservation/sustainable-living/at-home/rainscaping-guide/vegetated-bioswales.aspx

Bioswales are landscape elements designed to remove silt and pollution from surface runoff water. They consist of a swaled (Define this?) drainage course with gently sloped sides (less than six percent) and filled with a combination of vegetation, compost, and riprap.[1]:19 (this citation isn't working) The path of the flowing water, along with the wide and shallow ditch, is designed to maximize the time water spends in the swale, which aids capture of pollutants and silt. Depending upon the geometry of land available, a bioswale may have a meandering or almost straight channel alignment. Biological factors also contribute to the breakdown of certain pollutants.[2] Bioswales are often constructed around parking lots, where pollution from vehicles is collected by the paving and then flushed into the bioswale by rain. A bioswale, or other type of biofilter, wraps around the parking lot and treats the runoff before releasing it to the watershed or storm sewer. (add links to other items in Wikipedia, such as "biofilter")

As a type of Best Management Practice (BMP) bioswales can be implemented during either during the design or construction stage of a project.

Objectives & Benefits
Bioswales facilitate a swale (what does this mean?) by placing ditch blocks or weirs perpendicular to the flow path. The soil layers of bioswales treat water quality through peculation(??? percolation?), while the vegetation and microbes in a bioswale reduces total volume of storm water runoff (how do microbes reduce volume?). Bioswales increase groundwater infiltration and aquifer recharge. Bioswales can also act as multifunctional conveyance systems in that they channels storm water runoff and can be aesthetic part of landscape and improve biodiversity. ADD REFERENCES TO EACH SENTENCE, CHECK FACTS

Bioswale Vegetation
Like ecosystems, bioswales have different layers of vegetation: bottom groundlayer, side slope groundlayer, side slope understory, and side slope overstory. Common vegetation lining the bottom of bioswales include sedge, Juncus, Mimulus guttatus, and Ranunculus (This list is very much limited to a specific geography, is it possible to refer to plants in a generic sense instead of naming individual species for each of the areas of a bioswale?  What types of vegetation are these?  What attributes should the vegetation in these different locations have?  Do these lists change by climate zone?  For example, I don't think trees would be a good idea for a bioswale in a very arid area.). Common side slope groundlayer vegetation includes elymus glaucus, deschampsia cespitosa, bromus carinatus, and festuca occidentalis. Common side slope understory vegetation includes physocarpus capitatus, rosa nutkana, sambucus racemosa, and cornus stolonifera. Common side slope overstory includes abies grandis, alnus rubra, fraxinus latifolia, and thuja plicata.

Vegetation can be established in bioswales in several ways: sodding, seeding, and plug planting. Properly installed sod can provide some immediate vegetation benefits and immediate protection from erosion, but soil preparation is important. Sod strips should be rolled or tamped and secured with 3 staples or pegs after being laid perpendicular to the direction of flow. Seeding should be irrigated carefully before the rainy season. Bunch grasses, rushes, shrubs, and tress should be plug planted. NEED REFERENCES FOR THIS SECTION

Contaminants Addressed
Several classes of water pollutants may be captured in bioswales: silt, inorganic contaminants, organic chemicals and pathogens. For silt, these effects are resultant turbidity to receiving waters (REWRITE, not clear; CITE). Inorganic compounds may be metallic compounds such as lead, chromium, cadmium and other heavy metals. Lead is the most prevalent chemical of this class, deriving from automotive residue (e.g. surface spillage of leaded gasoline) (is this true everywhere around the world? If not, say where this is true). Other common inorganic compounds are macronutrients such as phosphates and nitrates. Principal sources of these nutrients are excess fertilization, which can cause eutrophication in receiving waters. Chief organic chemicals are pesticides from agricultural and urban landscaping. These chemicals can lead to a variety of organism poisoning and aquatic ecosystem disturbance. VAGUE, rewrite. Pathogens typically derive from surface runoff containing animal wastes and can lead to a variety of diseases in humans and aquatic organisms. REFERENCE EACH SENTENCE EXPLAIN HOW BIOSWALES DEAL WITH EACH POLLUTANT, this describes the pollutants but not how bioswales clean them.

Examples
Two early examples of scientifically designed bioswales for large scale applications are found in the western United States. In 1996 for Willamette River Park in Portland, Oregon 2330 lineal feet of bioswale was designed and installed to capture and prevent pollutant runoff from entering the Willamette River. Intermittent check dams were installed to further abet silt capture, with the outcome of reducing 50 percent of all suspended solids entering the river system.

A second example of a large scale designed bioswale is at the Carneros Business Park, Sonoma County, California. Starting in 1997 the project design team worked with the California Department of Fish and Game and County of Sonoma to produce a detailed design to channel surface runoff at the perimeter of a large parking area. Surface runoff consists of building roof runoff, parking lot runoff and overland flow from properties to the north of the project site. A total of two lineal miles of bioswale was designed into the project. The purpose of the bioswale was to minimize runoff contaminants from entering Sonoma Creek. The designed bioswale channel is grass-lined, but almost linear in form. Downslope gradient is approximately four percent and cross-slope gradient is approximately six percent.