By Emily Howe, aquatic ecologist
Green infrastructure solutions are wide-ranging, flexible and can be applied on different scales — from the house to broad landscape.
In some cases, like Seattle, clean drinking water is secured by watershed protection at the headwaters of the Cedar River. Rather than installing a water-treatment plant, the City of Seattle lets nature do the work of gathering and cleaning municipal water supplies. Other large-scale green-infrastructure investments include preserving and reconnecting floodplains to rivers, wetland protection and protection of trees.
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But green infrastructure can be much smaller scale as well. Home rain gardens, for example, capture runoff from roofs and driveways. These garden depressions allow water to percolate into the soil rather than running into street stormwater systems. Collectively, rain gardens can reduce flow volume to pipes, ensuring that storm events do not overwhelm municipal water-treatment plants and pipe systems. Other small-scale efforts include permeable pavement, green roofs, rainwater-harvest systems, trees and tree boxes, and infiltration planters.
Mid-scale, regional stormwater systems function a little differently, targeting problems associated with widespread impervious surfaces, such as streets and parking lots. Many municipalities have installed combination green/gray infrastructure systems, which intercept main-line stormwater pipes connected to large neighborhoods and business districts. In these cases, hundreds of acres can be treated by routing stormwater through engineered swales containing soils and vegetation. These swales slow, filter, and clean stormwater of its pollutants before reaching the outfall pipe to adjacent water bodies.