The USGS Water Science School
If you are not familiar with the term "impervious surface," this picture of a typical landscape in suburban Atlanta, Georgia, USA, will help explain it. As cities grow and more development occurs, the natural landscape is replaced by roads, buildings, housing developments, and parking lots. The metro Atlanta region has experienced explosive growth over the last 50 years, and, along with it, large amounts of impervious surfaces have replaced the natural landscape.
Impervious surfaces can have an effect on local streams, both in water quality and streamflow and flooding characteristics. In areas that have a lot of impervious areas, more runoff water enters local streams and also enters at a faster rate, which can result in local flooding. Water-quality problems can occur from development which disturbs the natural landscape. For example, if development is occuring alongside a tributary and proper sediment controls are not taken, then after a rainstorm, sediment-laden water from a tributary can contribute large amounts of sediment into larger rivers.
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