The hard surfaces of roads, sidewalks and parking lots interfere with the natural process of rainwater absorption, causing the water to puddle and run off into gutters and sewer systems, collecting pollutants along the way. Rain-capture solutions, however, can be used to reduce water runoff on public and private properties alike. Cities such as Los Angeles have passed laws emphasizing low-impact development to require the use of rain-capture devices in many new developments.
In 2006, the city of Philadelphia began installing porous pavements in selected public areas like basketball courts and schoolyards. The pavement looks like concrete, but it doesn't contain the fillers that make regular concrete impervious to water. When it rains, the porous concrete quickly absorbs the water, filtering it into a gravel bed below the top surface. Perviouspavement.org, a website developed and maintained by the National Ready Mixed Concrete Association, offers tips and advice for mixing porous concrete for contractors and do-it-yourself homeowners.
Porous cement isn't the only paving material that can help reduce rainwater runoff. The Clemson University Department of Horticulture Extension Service recommends using "permeable paving surfaces" for patios and walkways. These include modular paving materials and wood decks, both of which slow the runoff of rainwater and allow it to soak into the ground beneath the walkway, path, patio or deck.
According to the Clemson Extension Service, landscaping your property can also help slow rainwater runoff. Terraces are especially effective in slowing and capturing rainwater and are an attractive landscape solution for sloping yards. Many homeowners plant rain gardens, which are designed to capture the runoff from downspouts, gutters and driveways. A rain garden located close to the house will capture the runoff from the roof and downspouts, while one located further away can service the entire lawn or the patio.
Downspouts tend to concentrate runoff in one spot, contributing to erosion. Instead of directing the downspout onto the ground, point it into a rain barrel to collect rainwater for gardening and other outdoor tasks that require water. There are many specialty rain barrels on the market that include intake filters, runoff valves and hoses that allow you to draw off the water collected in the barrel for irrigating the garden, washing off garden tools or washing your car.