Low impact development has been acknowledged by the Water Environment Research Foundation as a sustainable stormwater practice. It is used to develop systems that imitate natural water movement processes. These systems facilitate the use of storm water as a resource rather than eliminating it as a waste product, effectively reducing the impact that an urban area may have on the local watershed. Preserving the hydrologic and ecological functions of ecosystems is an important aspect of an environmental engineer’s work. Prospective and practicing environmental engineers need to understand the utility of the following low impact development techniques, and how each one can be used to protect environments and infrastructure.
Rain barrels effectively reduce strain on residential sewerage infrastructure and promote water efficiency by diverting stormwater to storage systems that collect rain as it falls. The water can be filtered and used for consumption, irrigation, and other recreational uses, saving a modest amount of money that would otherwise be spent on public water utilities. The rain barrels are usually positioned under downspouts, allowing them to capture rainwater that would pour into local drainage infrastructure. As long as rain barrels are installed correctly and emptied at regular intervals in between heavy rain events, they effectively reduce strain on municipal drainage systems and flooding.
In a case study by the Insurance Bureau of Canada between 2012 and 2014, 1,000 rain barrels were provided to the small community of Stratford, Canada. The purpose was to measure the effect of rain barrels on the water drainage and treatment infrastructure by monitoring and analyzing the flow rates and precipitation records. At the end of this experiment, the engineers determined that the amount of rainwater being stored by the rain barrels accounted for an approximate 4.5% decrease in the flow of stormwater to Stratford’s wastewater treatment plant. This low impact development technique must continue to be enhanced by environmental engineers, because during peak storm events, this reduction in water flow could be enough to prevent drainage system overload and reduce flooding.
As defined by the U.S. Environmental Protection Agency, a green roof is a vegetative layer growing on the roof of a structure. Modern green roof technology has existed since the early 1970s, when the concept became popular in German communities. But recently, environmental engineers have determined that advancing the methods used to design effective infrastructure for green roof systems is necessary to improve environmental sustainability in urban environments.
Green roof technology is a low impact development technique that allows populated areas to sustain biologically diverse environments on rooftops, while also sparing the environment from pollution, excessive stormwater runoff, and high energy expenditures. Populations of flora and fauna can make their homes on green roofs, providing new species access to otherwise inaccessible areas. The plants also process carbon dioxide, store stormwater, and absorb excess heat effectively, meaning pollution is reduced, drainage systems receive less strain, and less energy is expended on cooling the buildings that have green roof systems installed.
Permeable pavers are low impact development solutions that use interlocking pieces of concrete pavement to reduce the amount of surface runoff generated on walkways, patios, driveways, parking lots, alleys, and other low volume roads. The 100% surface permeability offered by permeable pavers routes water directly to soil subgrades, rather than into sewerage systems. Permeable pavers consist of concrete pavers that are connected using stone filled joints, which store the water until it is able to flow through an open-graded bedding into a base and subbase aggregate.
The design and construction of permeable pavers has several important costs and benefits, but when engineers implement them correctly, the benefits make this low impact development technology very worthwhile. Permeable pavers have been shown to significantly reduce noise pollution, as the substances used in the components often have noise-reducing properties. Permeable pavers also help municipalities to manage stormwater runoff volume and improve water quality, as the interlocking pavement causes precipitation to run off faster than impermeable surfaces. It does so without relying on stormwater drainage systems that may flood and discharge pollutants into nearby surface water sources. Unfortunately, permeable pavers are a relatively new technology, so environmental engineers must contend with concerns regarding the maintenance costs of these pavers and develop new solutions to the potential risks of moisture damage that may reduce their effectiveness.
Engineering the most effective methods of allowing the stormwater in urban environments to be naturally absorbed and filtered by the soil is necessary to reduce the frequency of flooding events and to limit the amount of waste water. When communities adopt low impact development strategies, they reduce the negative impacts of stormwater runoff on their communities and watersheds. By reviewing these and other low impact development techniques, practicing environmental engineers can help keep groundwater sources potable and plentiful without placing unsustainable demand on urban infrastructure.
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