A large part of our city has been covered by pavement and buildings, which changes how rainwater moves and is absorbed into the ground. This cycle can wreak havoc on the soil around a house, but the management of stormwater on a property may be much simpler that one would initially think. Homeowners can employ a variety of low-impact development techniques to provide on-site collection and detention of rainwater, filtering of runoff and allowing groundwater recharge.
One technique to capture water is to use deep soil in shrub areas, which allows runoff to soak into the soil, so that plants will require less water. Also, provide linear, grass-lined depressed areas, called swales, to direct runoff to a permeable collection area. The use of materials that let water seep through, such as porous concrete or grass pavers for walkways and parking areas, can make a huge difference in the amount of water that stays on your property.
Disconnect downspouts and redirect rainwater to flow from gutters into rain barrels. This newly captured water can be used to water a garden.
Another idea is to create a rain garden. Rain gardens are simply a planted depression in the landscape that allows rainwater runoff from impervious urban areas like roofs, driveways, walkways, parking lots and compacted lawn areas the opportunity to soak into the soil. Well-designed rain gardens absorb 30 percent more rainwater than conventional lawns.
Rain gardens also clean runoff water. As water passes through the plant/soil mixture, chemical and biological processes break down pollutants. This helps protect the creeks and rivers in our area from oils, fertilizers and other pollutants carried by runoff.
A typical rain garden consists of native plants, deep well-drained soil, mulch and sometimes gravel. The surface layer of mulch or gravel slows and spreads water throughout the garden so that plant roots and soil can absorb the water.
The selected plants for a rain garden need to be able to withstand the extremes of both flooding and drought. Plants on the upper edges of the garden are often xeric, or dry, in their requirements, while plants placed in the deeper areas of the garden should be able to tolerate large amounts of water, as the soil there will remain saturated much longer after a rain.
Many species of plants found along river edges are particularly well suited to the extreme environments of rain gardens: native grasses like Gulf Muhly Grass and flowering shrubs such as Texas Star Hibiscus or Turk's Cap.
Studies have indicated that residential developments with natural landscaping, water-capture methods and permeable materials can reduce annual stormwater runoff volumes by as much as 65 percent. In our city, where the storm-drought cycle is so prevalent, the use of such techniques can help you do your part to help our city.
Larry Clark is a landscape architect and urban designer with Bender Wells Clark Design.