Impervious areas affect rainfall runoff, flooding, a

Impervious areas can affect precipitation runoff and flooding, and water quality

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.

And, notice in the foreground the housing units under construction, and the exposed dirt that accompanies construction. Rainfall falling on these exposed area can cause severe sediment runoff, which can get into local creeks and cause water-quality problems. 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.

Find out more

• Impervious Surfaces and Flooding

• Why is this house wearing stilts?

• Sediment and suspended sediment in rivers

• Runoff (surface water runoff)