What is Green Infrastructure?
Green infrastructure uses natural processes to mimic nature for managing storm water. In technical terms, biomimicry, or copying nature, utilizes the same processes and systems found in a natural environment, before land development. These systems and processes are employed to solve stormwater issues.
Simply put, as buildings and structures were developed and constructed, the naturally occurring systems to handle stormwater were disturbed. These disturbances led to an increase in stormwater runoff. Roads were built, homes were built, and the soil was compacted by construction equipment. These disturbances led to a significant increase in impermeable surfaces or, in other words, surfaces that did not allow water to percolate through to the soil. The result – both the volume and the peak flow of storm water increased. The increase in stormwater runoff is significant. While this method of construction and stormwater management was conventional forty years ago, we are now seeing some of the pitfalls of this approach.
In a natural environment, prior to development, ninety-eight percent of the stormwater that fell on any given property stayed on the property. The leaves of the trees that covered the property as the rain fell, initially slowed the rain down. The soil, which was permeable and not compacted, captured the majority of the rainfall. Only two to three percent of the rain that fell on a certain area ran off across the surface area. The velocity of the water runoff was significantly slower because of the vegetation covering that area.
The problems created by the increasing velocity and flow of storm water has resulted in a significant number of problems. Stream banks are eroding and threatening to undermine building foundations. In some cases expensive shoring has been installed to prevent the loss of property. In many areas, subterranean HVAC ductwork on some properties is collecting water resulting in mold and mildew. Subsurface water is surfacing on roadways resulting in flooding. In freezing conditions, icy roads and walkways create safety issues.
Why Green Infrastructure?
Green infrastructure is the latest and most effective development in land use planning. Many businesses and communities would like to utilize the best stormwater management practices available. Green infrastructure was developed in the United States in the mid 1990’s as a means to address a growing concern about the increasingly severe problems associated with stormwater issues. Stormwater, or non-point source water, is the largest source of water pollution in America. The conventional technology used fifty years ago to handle stormwater was to rapidly collect it and pipe it away via engineered collection systems. As noted earlier, the conventional technology of fifty years ago has created serious issues and is no longer an effective means to stormwater solutions. Traditional infrastructure has been refined. Green infrastructure employs the most advanced methods and techniques for managing stormwater.
What are the Elements of Green Infrastructure?The elements of green infrastructure utilize soil and plants, or vegetation, to manage stormwater. Additionally, in developing a green infrastructure approach we examine the stormwater production as far upstream, as close to the source of the stormwater production, as possible.
There are two recommended primary elements:
1. Downspout Disconnections or Extensions
2. Rain Gardens and Bioswales
Downspout Disconnections or Extensions
The largest source of stormwater runoff occurs from rain falling on rooftops. Many rooftops currently have a stormwater collection system installed complete with gutters and downspouts. However, in some cases the downspouts drain into pipes that surface on a downgrade and the stormwater flows onto adjoining condominium areas. In other cases, the downspout outflows are not piped anywhere. They simply drain out onto the surface of the property. Finally, some downspout outflows are directed onto roadways and driveways.
[Insert roof runoff here
Downspout disconnections and extensions require directing the stormwater from the downspouts into a permeable area, such as a rain garden or bioswale, as close to the source as possible. The storm water is not directed onto another impermeable surface like a roadway or driveway, as is the situation often seen today.
Downspout disconnections and extensions are the simplest and least expensive way to mitigate the stormwater issues quickly. Additionally, this benefits the environment because it helps to restore the natural water cycle.
Rain Gardens and Bioswales
Rain Gardens and bioswales are vegetated areas, lower in elevation than the surrounding area, with engineered soil that allows rainwater to be percolated through a series of soil and gravel layers. The purpose of a rain garden or bioswale is two fold. First, the rain garden or bioswale captures and detains storm water. Second, the rain garden or bioswale filters the storm water, thus reducing stormwater runoff and pollution.
Rain gardens and bioswales are located in an area as close as possible near the structure that produce the stormwater runoff. Native plants are usually used for vegetation because native plants are more adaptable to the local climate and do not require as much maintenance as turf or other plant materials. The vegetation in a rain garden or bioswale maintains the soil’s permeability and assists in filtering the storm water.
Rain garden and bioswales should be designed and engineered to capture one hundred percent of a one-inch rainfall. Ideally, the one-inch rainfall event will be retained for at least eighteen hours but not more than seventy-two hours.
Conclusions
Embarking on a multi-year project that aims to reduce and eliminate many of the stormwater issues experienced since development while restoring the natural water cycle is one that takes informative, collaborative effort. This kind of forward thinking, integrated, and long-range planning approach will combine the existing traditional infrastructure with newer techniques in green infrastructure. The result will be a sustainable approach to stormwater mitigation that will be effective, resilient and less expensive in the long-term, than conventional stormwater management. Additionally, green infrastructure is more than just mitigating stormwater. The solutions recommended will have a positive, long lasting impact on the environment.
Recently, I spoke at the Great Lakes Awareness Event hosted by Patagonia Chicago.
I am excited to be participating in the Great Lakes Awareness Event with Patagonia, the sportswear and outdoor apparel retialer in Chicago.