A green roof is the roof of a building which is partially or completely covered with vegetation. A green roof may consist of features such as a drainage system, filter cloth, root repellant layer, and thermal insulation. Green roofs reduce stormwater runoff by reducing, retaining and delaying runoff during rainfall events.

Permeable pavement is a type of hard surface ground cover that is porous, allowing rainwater to pass through into the ground beneath. This system mimics the process that would occur when rain falls onto natural surfaces, such as a forest floor. Permeable pavement can also trap suspended solids and pollutants, which allows for cleaner water to returned back to underground aquifers.

Invasive plant species removal consists of removing vegetation that is non-native to the ecosystem in which it has been found. Invasive species often take over native systems and can cause damage to the environment and/or human health. In many situations, invasive species removal may be done as a first step before native plants and trees are planted.

Depaving is the process of removing unnecessary pavement which contributes to stormwater pollution. Removing these impervious surfaces also allows for the creation of community green spaces and increases the land available for urban farming and habitat restoration. In some cases, a site may be depaved, and then turned into a rain garden.

Rainwater harvesting involves collecting and storing rainfall for re-use or release into the landscape or sewer system and can range in scale from a single rain barrel to large commercial storage facilities.

Tree planting activities consist of planting native vegetation in both urban and rural settings. This is often done to restore fish and wildlife habitat and reduce erosion. Trees and other vegetation reduce stormwater runoff by providing a canopy layer that rain lands on and evaporates. The roots of trees also take up rainwater and help allow healthy soil to infiltrate.

A rain garden is a bowl-shaped garden designed to capture and filter stormwater runoff from roofs, driveways and other hard surfaces, keeping it from becoming harmful water pollution. Rain gardens are relatively simple to install and feature well-draining soil and easy-to-maintain plants that allow for stormwater infiltration. For simplicity we define “Rain gardens” as an inclusive catch-all for simple as well as engineered, small as well as large versions of this concept, including: Bioretention facilities, stormwater planters, Bioswales etc.