LID, or Low Impact Development, is a method of design using green infrastructure to control both the quality and quantity of stormwater runoff. The practice began as an alternative to regular BMPs on construction sites after it was determined that traditional practices, such as ponds, generally didn’t do much for water quality goals or cost effectiveness. The primary goal is to try and recreate or preserve the area’s natural hydrology. Basically most elements of urban development and infrastructure, including roofs, sidewalks, roadways, and medians all have the potential to serve as components in this type of design.
Types of LID
- Rain Gardens: Instead of sending runoff overland and through different pesticides, fertilizers, and other chemicals? to be directly swallowed up by the storm drain, implement a rain garden. This is simply a small and attractive planting bed meant to work like a sponge to filter the water and allow it to seep into the surrounding soil.
- Green Roofs: They help to filter, absorb, and detain rainfall with lightweight soils and specialized plants meant to thrive in harsher, dryer, high temperature environments. These green roofs can not only help to reduce runoff by slowing down the flow of water into the storm drain system, but they also help to remove airborne pollutants and prevent them from polluting water runoff. These are also known to extend the life of your roof!
- Permeable pavers: Instead of traditional asphalt and paving practices, permeable pavers provide the ability for water to, instead of running directly into a storm drain, percolate through the ground. Permeable pavers help to reduce suspended solids from water, many of which are considered pollutants.
- Rain barrels and cisterns: This is simply the practice of retaining rainwater in a detention device. You can then use this water later for different purposes, such as lawn or garden watering, or as a secondary supply of water.
- Tree box filters: These function as mini bioretention areas below the trees. The runoff is directed to these areas, the water filtered by soil and vegetation, and then serves as irrigation for the tree from where it is collected in a catch basin.
What does it cost?
Although costs will vary greatly depending on the site and the conditions within the site, there are some general cost benefits that are commonly seen with the use of LID projects. These include lower lifetime costs, environmental and social benefits, reduced offsite costs, the functional use of space, and a relatively low maintenance requirement.
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