Concrete can impair water quality by increasing polluted runoff.
While concrete may seem like a harmless part of the environment, its presence can pose environmental risks in some areas. A 2007 study by the NOAA National Geophysical Data Center estimates that just over 1 percent of the entire surface of the United States is covered by impervious surfaces, including concrete. This figure breaks down to 297 square meters per American. In areas of urban development, the environmental issues it causes are most acute.
Nonpoint Source Pollution
One of the greatest environmental issues associated with concrete is nonpoint source pollution (NSP). NSP can come from a wide range of sources, including automobiles, agricultural runoff and other pollutants introduced into the environment. Concrete provides a means for precipitation washing over its surface to move these contaminants quickly over a wide area. The risk exists that this polluted runoff will enter water resources, possibly contaminating drinking water or impairing recreational water resources.
Flood Risk
Concrete surfaces also increase the risk of flooding. Impervious surfaces such as roads and parking lots do not absorb excess water caused by precipitation. Instead, water has no place to go but to flow freely over concrete. By acting as a barrier to penetration in the soil, the concrete surface allows water to flow unimpeded, so the dangers of flooding increase. Urban areas are at the greatest risk of floods due to their higher concentrations of concrete on impervious surfaces. Low-lying areas and floodplains are also vulnerable to an elevated flood risk due to concrete surfaces.
Soil Erosion
Concrete poses an additional danger of soil erosion. The speed of flowing water over these surfaces can cause erosion along edges of concrete, dumping sediments and other contaminants into waterways. The sediment may contain pollutants, which can harm freshwater ecosystems. The increased cloudiness of water resources can lead to wildlife and plant die-offs in species that cannot tolerate these conditions. An increase in sediment can prevent sunlight from reaching submerged plants, affecting plant growth. These conditions can worsen water quality in affected areas.
Mitigating Risks
The environmental issues that concrete causes either directly or indirectly warrant careful land-use planning, especially in areas where water flow goes directly into lakes and streams. Options for city planners include limiting the amount of concrete surfaces. In areas where it is deemed necessary, alternative choices, including pervious concrete pavement, can replace regular concrete on pedestrian paths and some road surfaces, explains the U.S. Environmental Protection Agency. In this way, people can benefit from having concrete surfaces for travel, while reducing concrete's impact on the environment.
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