SierraScape October - November 2006
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Scott Woodbury, manager of the Whitmire Wildflower Garden at Shaw Nature Reserve, with a presentation on Rain Gardens which use natural features and native plants to slow and control stormwater runoff.

The problem: Government studies have shown that up to 70% of the pollution in our aquifers, rivers, lakes and coastal areas is carried there by storm-water runoff. Storm-water runoff comes from rooftops, roads, driveways, sidewalks, parking lots, even mowed lawns, which do not absorb water effectively and create fertilizer and pesticide runoff. These impervious surfaces have taken the place of soil that readily absorbs rainwater. The result is an increase in storm-water volume and velocity creating an increase in water pollution, stream bank erosion and flooding.

A natural solution: In nature, plant life reduces storm-water runoff on hillsides, along stream and riverbanks, and in low-lying wetlands (these areas are called a watershed). Throughout a watershed, living plants aerate soil, slow down water and help water percolate into the ground, thus reducing erosion and flooding. Unfortunately, healthy natural watersheds and their associated plant communities have been damaged and/or destroyed by urbanization.

Rain gardens function like miniature natural watersheds. They slow down, capture and absorb water using elements similar to those in nature: plants, rocks, shallow swales and depressions that hold water temporarily rather than let it quickly run away. Rain gardens improve water quality in lakes and rivers by reducing siltation, and they minimize flooding and loss of soil. They reduce costs associated with topsoil loss in agriculture and reduce erosion damage along river edges. Use of rain gardens also can save tax dollars by reducing the need for communities to build larger storm-water retention facilities. They provide beauty, natural diversity and wildlife habitat in areas that otherwise would be a monoculture of lawns, pavement, concrete culverts and storm drains. This landscaping style increasingly is used by homeowners, commercial and residential developments, and by cities for park beautification.