Permeable/Pervious Pavements

Permeable pavements are porous concrete or asphalt that allows water to run through, or infiltrate, into the surrounding soils and groundwater. These pavements are used as part of a larger stormwater site management system. Polluted stormwater moves through the pavement surface though a base and sub base with spaces, or voids, utilizing crushed gravel, sand and occasionally, geotextiles. Permeable pavement is used in areas with less heavy traffic such as parking lots, neighborhoods, sidewalks, trails and highway shoulders.


Bioretention includes bioretention cells and swales which uses soils, plants, trees, shrubs, and grasses to improve water quality, reduce flooding and convey, or direct, stormwater away from critical infrastructure. Bioretention cells may or may not have an underdrain and are not designed as a conveyance system. Bioretention swales are designed as a conveyance system.

Rain gardens

Rain gardens, are shallow depressions in the land filled with native soil or soil mix, plants and other vegetation that captures and in some cases, filters, stormwater from adjacent areas. Even though rain gardens are a type of bioretention, they have different permit requirements. For more information on the differences between bioretention and rain gardens, please read this article.

Green Roofs

A green roof is a roof partially or fully covered with vegetation and a growing medium which is planted over a waterproofing membrane. It can contain edible plants and walkable gardens. Green roofs reduce and slow stormwater, reduce urban heat island effect, and reduce energy use, air pollution and green house gas emissions.

rainwater catchment

Rainwater collection is a method of collecting and storing rainwater from rooftops, land surface,  or rock catchments. The system includes catchment, pre-treatment, storage, treatment, use, reuse and operations and maintenance. Physical components include a roof, gutter or roof drain and a piping system to convey the water to and from a storage tank or cistern. In Washington State, you do not need a water right for rooftop collection and use.

LID Research at WSU Puyallup