How to Solve Storm Runoff While Staying Green
Storm drains in the San Francisco area discharge directly into San Francisco Bay, thereby allowing the water to carry surface debris and chemical pollutants with it. These pollutants destroy local fisheries, cause algal blooms and alter the local ecology, so mitigating strategies are clearly necessary. Re-designing storm drains is not realistic given the extreme costs involved, so what can the metropolitan area do to solve these problems?
The answer is a concept called Low Impact Development, or LID. The primary principle behind the concept is that trees and other types of “green infrastructure,” can help reduce the problems associated with storm runoff – primarily by virtue of their water-storing abilities. In this way, LID principles seek to manage rainwater where it falls, rather than by transporting it to another location. In addition to being highly efficacious, LID is less expensive than traditional water management strategies.
LID proponents embrace a variety of different strategies, techniques and tactics, such as those listed below.
Perhaps unsurprisingly, given the diverse array of other benefits street trees provide, street trees are helpful for reducing runoff water. While trees planted in rain gardens must be flood tolerant to withstand the saturated soil conditions, virtually any trees that are otherwise well suited for urban settings can make suitable street trees, by placing them at various elevations within the watershed.
Rain gardens are patches of flood-tolerant plants and trees, which can be placed in a variety of elevations within a watershed. By directing runoff water to flow across such areas, the vegetation and substrate slow down the water, so the plants and trees can absorb more of it.
Swales and Curb Cuts
Swales are vegetated areas, placed in the path of a runoff channel -- for example, a median containing small trees and ornamental plants. Small voids are cut into the curb, which divert the runoff water into the swale, thereby allowing the vegetation and soil contained within the swale to absorb some of the water.
Plant- or grass-covered roofs greatly reduce the amount of runoff water traveling through gutters and down downspouts. Green roofs can be placed on the roofs of commercial buildings as well as residential homes.
By connecting large tanks to the rain gutters of buildings, you can stop vast quantities of rainwater from reaching the ground at the same time. This not only reduces the amount of runoff water flowing down the street, but it provides surplus water for other needs, such as irrigation.
Many runoff problems can be solved by replacing concrete sidewalks and roads with surfaces that allow water to percolate to the soil below. Pervious pavements and paving stones feature numerous holes that allow water to pass through.
Part of the beauty of LID principles is that they are applicable to landowners and municipalities alike. If you are interested in implementing LID features, contact Homescape Now and consult with one of our experienced landscape technicians. He or she can then help you select the best species for your tree installation project.