Sourced from Total Landscape Care
Buildings, paved roads, parking lots and concrete sidewalks comprise significant expanses of hardscapes in urban areas.
During periods of heavy precipitation, runoff is to be expected due to the impervious nature of these surfaces. It is estimated that stormwater runoff may be as high as 55 percent of total precipitation in urban areas.
Other factors that may lead to runoff include compacted soils with poor drainage, due to lack of pore space, which are commonly encountered in urban environments. Negative consequences of stormwater runoff include: slope erosion, exceeding capacity in municipal waste water treatment systems and incursion of chemicals, oils and fertilizers into natural bodies of water.
Such pollutants and their sources include: pesticides, copper from automobile brake pads, zinc and lead found in roofing products and phosphorus and nitrogen contained in fertilizers. Extreme levels of phosphorus in the water can cause eutrophication (which is the buildup of nutrients in natural bodies of water).
Eutrophication may lead to algal blooms, which are fed upon by microorganisms. As the microorganism populations increase and eventually die, the oxygen in the water becomes depleted, which harmfully affects fish and aquatic wildlife.
Natural settings like forests, open fields and wetlands are more efficient in processing stormwater. This is affected by greater water infiltration into those highly permeable soils. This natural process can be simulated in urban environments with the use of green infrastructure (GI).
A simple description of GI is “constructed features that use living, natural systems to provide environmental services, such as capturing, cleaning and infiltrating stormwater; creating wildlife habitat; shading and cooling streets and buildings; and calming traffic.”
Among the benefits of GI are: amelioration of temperatures in urban areas, improved aesthetics of streets and sidewalks and minimizing and cleaning stormwater runoff. Several forms of GI can be utilized in urban settings, including: urban forests, green roofs, rain gardens and bioswales.