Hard surfaces

Increases in hard surfaces such as pavement, roads and housing development have an impact on the process of run-off, infiltration and erosion. When trees and natural vegetation cover is replaced with hard surfaces the water runs off more quickly and soaks in less.

Hard surfaces may cause:

• an increase in flooding due to less water being retained in the soils, wetlands etc.
• a decrease in water quality due to a reduction in sediment trapping
• an increase in erosion due to increased run-off and concentration of flow into one area, i.e. when it comes out of a drain or gutter.

Quick facts

When 10%

of a catchment is covered in impervious surfaces, many types of pollution sensitive aquatic insects decline by as much as one third, compared to streams in undeveloped forested watersheds. Studies have shown that there is no ‘safe zone’, meaning that even minimal development can negatively affect aquatic life in urban streams.[1]